WO2010014015A1

WO2010014015A1 - Tablet manufacturing method

Info

Publication number: WO2010014015A1
Application number: PCT/NZ2008/000190
Authority: WO
Inventors: Fadil Al Alawi; Karthigeyan Nanjan; Wayne Frederick Leech
Original assignee: Bomac Research Limited
Priority date: 2008-07-29
Filing date: 2008-07-29
Publication date: 2010-02-04
Also published as: BRPI0822980A2; AU2008360070A1; AU2008360070B2; ZA201101565B

Abstract

A method of manufacturing a tablet formulated for administration to an animal containing at least one macrocyclic lactone compound and at least one additional compound with anthelmintic activity by the steps of: (a) dissolving the macrocyclic lactone compound or compounds in at least one organic solvent; (b) combining the mixture of step (a) with at least one organic co-solvent; (c) combining the mixture of step (b) with: i. at least one additional compound with anthelmintic activity; ii. at least one binder compound; iii. at least one filler / bulking agent compound; and, (d) drying the mixture of step (c).

Description

TABLET MANUFACTURING METHOD

STATEMENT OF CORRESPONDING APPLICATIONS

This application is based on the Provisional specification filed in relation to New Zealand Patent Application Number 552292, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The invention relates to a tablet manufacturing method. More specifically, the invention relates to a method of manufacturing a tablet formulation containing at least one lipophilic compound with anthelmintic activity and at least one further anthelmintic compound for use in treatment of an animal

BACKGROUND ART

Anthelmintic chemical compounds are widely known agents that are destructive to worms and used for treating internal and external parasitic infestations in animals including humans.

There are many different types of anthelmintic compound, each with varying degrees of parasitic activity and chemical properties.

A difficulty in formulating such compounds is that many are extremely insoluble in aqueous environments such as extracellular fluids, thus they need to be formulated to make them bioavailable. In addition, in order to make these compounds soluble, different conditions may be required resulting in situations where one compound may be solubilized by for example, by reducing pH. This change can cause other compounds in the formulation to become insoluble, or the change may cause physical or chemical degradation of another compound in the formulation. In addition, the change may cause adverse side effects in the animal.

Stabilising and providing combinations of anthelmintic agents for oral administration have been considered in the prior art. A wide variety of advantages may be obtained by such combinations and these are discussed in prior art patent specifications including WO 00/74489 and WO 02/09764, incorporated herein by reference.

In the present invention, an aim is to provide a method of manufacturing a tablet formulation containing at least two different anthelmintic compounds from different families of anthelmintic activity where these compounds would not normally be able to be mixed together. A further aim is to increase the bioavailability of a lipophilic compound with anthelmintic activity.

A problem found in the prior art with existing anthelmintic compounds including benzimidazole anthelmintics is the need to deliver the compound as an oral suspension due to the poor solubility of this type of compound in aqueous environments. One preferred method of administration is by injection however, as the solubility of the anthelmintic is often poor, drugs delivered by injection are not always readily absorbed and often may cause pain to the animal or human absorption or precipitate formation.

The macrocyclic lactone family of anthelmintic compounds, which family includes abamectin and ivermectin, present a different challenge again with such compounds being lipophilic and largely insoluble in aqueous environments. It should be appreciated that providing a tablet formulated to include one or more anthelmintic agents is a challenge particularly where the agents are lipophilic, require specific conditions in which to dissolve or may lose viability when stored over time. Another problem specific to tablets is ensuring that the tablet dissolves on administration and releases the active agents in a form that is bioavailable and does not simply pass through the animal without achieving the desired therapeutic effect.

One attempt to address the above problem is an albendazole capsule for the treatment of gastrointestinal parasites in adult sheep and lambs (marketed in New Zealand as [EXTENDER® 100). This product is formulated to provide a slow release of albendazole to 'control' parasites over a time period of 100 days. A disadvantage of this product is the continuous release of albendazole at levels below that required to kill adult parasites. The drug levels are designed to the kill incoming larvae, which require a lower dose rate for control than adult parasites - in effect the product's main use may be as a prevention method and not to address infestation once it occurs. Besides not addressing adult parasites, use of the product may lead to drug resistance where the low dose allows adult parasites to become resistant to the ivermectin. Further reinforcing the resistance problem is that, when this product is given to adult ewes, drug resistant parasites may also be transferred to progeny from the ewes prolonging resistance across different generations. A further problem with the above slow release capsule is that the time period between delivery and slaughter must be sufficiently long to ensure all agent has been released. By contrast, fast release products are more flexible as the time period between delivery and slaughter may be significantly shorter.

Another product is a slow release capsule containing ivermectin (marketed in New Zealand as IVOMEC® Maximiser™ CR). It gives a slow release of ivermectin over 100 days with ivermectin levels dropping below that required to kill adult parasites for a substantial amount of that time. It consequently suffers from the disadvantages previously described.

It should be appreciated that it is desirable to have a formulation:

• for delivery of parasinoidal compounds including lipophilic agents,

• which stabilises these agents so that they may be stored over time with minimal physical or chemical degradation, and

• delivers a consistent dose of the agents on administration to an animal.

It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.

All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.

It is acknowledged that the term 'comprise' may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term 'comprise' shall have an inclusive meaning - i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term 'comprised' or .'comprising' is used in relation to one or more steps in a method or process.

Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.

DISCLOSURE OF INVENTION

According to one aspect of the present invention there is provided a method of manufacturing a tablet formulated for administration to an animal containing at least one solubilisable lipophilic compound with anthelmintic activity and at least one additional anthelmintic compound formed by the steps of:

(a) dissolving at least one of the solubilisable lipophilic compound or compounds in at least one organic solvent;

(b) mixing the mixture of step (a) with at least one co-solvent;

(c) mixing the mixture of step (b) with:

i. at least one additional anthelmintic compound;

ii. at feast one binder compound;

iii. at least one filler / bulking agent compound; and,

(d) drying the mixture of step (c).

For the purposes of this specification, the term 'tablet' refers to the formulation being administered orally and in a consistency able to be administered as a granular material, discrete tablet or capsule, or alternatively expelled by device such as a 'pill popper¹, stomach tube or other delivery device. Preferably, at least one of the anthelmintic compounds used in the tablet may be characterised by being lipophilic and having poor solubility and/or poor dispersion characteristics in an aqueous environment. It is understood by the inventors that this poor solubility and/or poor dispersion may result in corresponding poor oral absorption, which may lead to poor pharmacokinetics. These factors may contribute to the compound having poor oral bioavailability. If such a compound is administered absent of a suitably formulated delivery system, the compound may either not be absorbed or be only poorly absorbed within an aqueous environment such as the blood stream.

Preferably a compound may display 'poor oral bioavailability' if, when orally delivered to an animal on its own (i.e. absent of a suitably formulated delivery system), it achieves less than approximately 20% absorption of the compound into the blood stream when compared with the results obtained using an equivalent single active orat drench.

Preferably, an 'aqueous environment¹ may be extracellular fluid.

In a further embodiment, the method includes a further step (e) after step (d) of:

(e) mixing the dried mixture of step (d) with at least one further compound with properties selected from: a disintegrant, a glidant/free flowing agent; a lubricant; and combinations thereof.

In a yet further embodiment, the final mixture after step (d) or step (e) if present may be compressed into a tablet.

Preferably, the solubilisable lipophilic active compound is a macrocyclic lactone. Preferably, the solubilisable lipophilic anthelmintic compound is abamectin or ivermectin. More preferably, the solubilisable lipophilic anthelmintic compound is abamectin, although it should be appreciated that as ivermectin also has similar lipophilic properties to abamectin, ivermectin is also encompassed within the present invention.

Preferably, the solubilisable lipophilic compound or compounds included in the tablet are at a dose sufficient to: prevent growth of parasites; reduce parasite numbers; kill parasites; kill incoming parasite larvae; lower the number of surviving incoming parasite larvae; kill or reduce the number of hypobiotic state parasites; and combinations thereof.

Most preferably, the tablet includes sufficient solubilisable lipophilic compound or compounds to provide the animal with a dose of the compound or compounds equivalent to that which would be obtained from an oral drench containing the same lipophilic compound or compounds.

Preferably, where abamectin is present, the abamectin is included at a rate of at least approximately 0.2mg to 0.6 mg of abamectin or ivermectin per kg of animal body weight. More preferably, the rate is approximately 0.2 mg/kg. Most preferably the rate is approximately 0.4mg/kg.

It should be appreciated that the doses described above are sufficient to kill or at least reduce parasite infestation including both larvae and adult parasites.

In one embodiment of the present invention, the amount of active ingredient per tablet for a cattle formulation is 64mg abamectin per tablet dosed to an animal weighing approximately 160kg. It is the inventor's experience that this level of abamectin provides a blood level of abamectin to the animal equivalent to that which would be obtained from an oral drench containing abamectin such as the product Genesis™. It should be appreciated that the dosage of abamectin may be varied depending on the amount of abamectin desired to be administered and that levels of abamectin above or below 64mg may be used without departing from the scope of the invention. Similarly, the dose may be varied for different animals.

Preferably, the solubilisable lipophilic compound is formulated to be rapidly released on oral administration.

Preferably, the solubilisable lipophilic compound is formulated so that the compound or compounds remain present in the bloodstream of the animal for at least 24 hours.

Preferably, the solubilisable lipophilic compound is formulated so that the compound or compounds dissipate from the bloodstream of the animal in a similar manner as an oral drench. It is understood by the applicant that the compound has left the blood stream after a time period of no more than two weeks.

Preferably the additional anthelmintic compound or compounds added in step (c) are compounds with different spectrum anthelmintic activity than the solubilisable lipophilic compound used in step (a).

In one embodiment, the anthelmintic compound added at step (c) is a substituted or unsubstituted benzimidazole compound. Preferably, the substituted or unsubstituted benzimidazole compound includes the structure:

where n = 1 or 2;

where R₁ which may be the same or different at each occurrence = H₁ Cl, -SC₃H₇, -SOC₃H₇, -SC₆H₅, -SOC₆H₅, -C₄H₉, Or -OC₆H₃CI₂; and, where R₂ = -NHCO₂CH₃ or -SCH₃.

Preferably, the substituted or unsubstituted benzimidazole compound may be selected from: albendazole, ricobendazole, fenbendazole, oxfenbendazole, parbendazole, triclabendazole and combinations, analogues and derivatives thereof. Most preferably, the benzimidazole compound is albendazole.

Preferably, the substituted or unsubstituted benzimidazole compound or compounds included in the tablet are at a dose sufficient to: prevent growth of parasites; reduce parasite numbers; kill parasites; kill incoming parasite larvae; lower the amount of incoming parasite larvae; and combinations thereof.

In a preferred embodiment, the tablet includes sufficient benzimidazole compound or compounds to provide the animal with a dose of the compound or compounds equivalent to that which would be obtained from an oral drench containing the same benzimidazole compound or compounds.

Preferably, where albendazole is present, the albendazole is included at a rate of at least 1 mg albendazole per kg of animal body weight.

In one embodiment, albendazole is included at a rate of approximately 3.7 mg albendazole per kg of animal body weight where the animal is a sheep.

In an alternative embodiment, albendazole is included at a rate of approximately 7.5 mg albendazole per kg of animal body weight where the animal is a bovine.

It should be appreciated that this dose is sufficient to kill or at least reduce parasite infestation including both larvae and adult parasites.

In one particular embodiment of the present invention, the amount of active ingredient per tablet for a cattle formulation is 1200mg albendazole per tablet dosed to an animal weighing approximately 160kg. It is the inventor's experience that this level of albendazole provides an oral bioavailability equivalent to that which would be obtained from an oral drench containing albendazole such as the product Valbazen™. It should be appreciated that the dosage of albendazole may be varied depending on the amount of albendazole desired to be administered and that levels of albendazole above or below 1200mg may be used without departing from the scope of the invention. Similarly, the dose may be varied for different animals for example the varied doses described above between sheep and cattle.

Preferably, the benzimidazole compound or compounds are formulated to be rapidly released on oral administration.

Preferably, the benzimidazole compound or compounds are formulated so that the compound or compounds or its active metabolites remain present in the bloodstream of the animal for at least 12 hours.

Preferably, the benzimidazole compound or compounds are formulated so that the compound or compounds or its active metabolites dissipate from the bloodstream of the animal in a similar manner as an oral drench. It is understood by the applicant that the compound has left the blood stream after a time period of no more than one week.

Preferably, the benzimidazole raw material is a dry micronised particulate powder. The inventors have found that micronised powder is a further key property. Without a micronised particle structure, the desired degree of oral bioavailability may be difficult to achieve.

In a further embodiment, the additional anthelmintic compound added to the mixture in step (c) is levamisole. Preferably, where levamisole is present, the levamisole is levamisole hydrochloride (HCI) included at a rate of approximately 5 to 9 mg levamisole per kg of animal body weight. More preferably, approximately 7.5 mg levamisole per kg of animal body weight.

In a yet further embodiment, both a substituted or unsubstituted benzimidazole compound and levamisole HCI compound are added in step (c).

Preferably, the solubilisable lipophilic compound is dissolved in at least one organic solvent. Preferably, the solubilisable lipophilic compound is subsequently mixed with at least one second organic solvent (termed a 'co- solvent' for the purposes of this specification). Preferably, the solvent or solvents and co-solvent or co-solvents are different compounds.

Preferably, the first organic solvent or solvents may be selected from: an alcohol, a glycol, an ether, a pyrrolidoπe with two or more carbon atoms, and combinations thereof. More preferably, the solvent or solvents may include: ethyl alcohol, benzyl alcohol, phenethyl alcohol, ethyl benzyl alcohol and other aromatic monohydric alcohols; glycols, glycol ethers, glycol ether acetates, C₁ to C₈ alkyl pyrrolidones, and combinations thereof. In a preferred embodiment, the solvent is benzyl alcohol which is preferred as it not only dissolves the solubilisable lipophilic compound, but also, acting with the co-solvent, stabilises the compound increasing the overall stability of the product.

Preferably, the co-solvent or co-solvents are alcohol or ether compounds with three or more carbon atoms. More preferably, the co-solvent or co-solvents include: diol alcohols or ethers including glycols, aromatic monohydric alcohols, glycol ethers, glycol ether acetates, and combinations thereof. In a preferred embodiment, the co-solvent is a propylene glycol compound such as monopropylene glycol which is preferred as it not only mixes with the solubilisable lipophilic compound and solvent but also stabilises the compound increasing stability and provides emulsifying properties. It is understood that the emulsifying properties assist in preventing crystallisation / precipitation of the lipophilic compound on release in the gut although other factors may also account for the increased bioavailability effect and this description should not be seen as limiting.

A further advantage of the organic solvents and co-solvents chosen are that they improve oral bioavailability by conferring a transmucosal effect on the tablet formulation whereby the solvents and co-solvents assist in transfer of the agent - or agents from the gut and into the animal bloodstream.

Without use of the above solvents and co-solvents, the solubilisable lipophilic compound or compounds would pass straight through the animal on administration with no or only sparing absorption. By dissolution and mixing with solvents and co-solvents, the solubilisable lipophilic anthelmintic compound is increased in oral bioavailability.

Preferably, the tablet as described above includes a ratio of solubilisable lipophilic compound to solvents and co-solvents within the range of approximately 1 part lipophilic compound to 0.8-1.2 parts organic solvent to 3.2- 3.6 parts organic co-solvent.

Preferably, the binder in step (c) is a pyrrolidone compound. More preferably, the binder is a polyvinyl pyrrolidone compound.

Preferably, the filler, disintegrant, glidant/free flowing agent and lubricant used in , steps (c) and step (e) if present include: corn starch, sodium starch glycolate, silica or silica based compositions, magnesium stearate or other anionic salts.

In a further embodiment, additional inert compounds may also be added. Preferably, drying in step (d) is completed by air drying at 40⁰C. It should be appreciated that the formulation may be dried using other methods including spray drying, freeze drying and the like without departing from the scope of the invention.

In preferred embodiments, the tablet produced by the method disintegrates within approximately 15 minutes when placed in water at 37°C.

In one embodiment of the present invention, the amount of active ingredient per tablet for a cattle formulation is 64mg abamectin, 1200mg levamisole HCI and 1200mg albendazole per tablet dosed to an animal weight of approximately 160kg. It is the inventor's experience that these levels of agent provide sufficient oral bioavailability to the animal on administration that blood levels obtained are equivalent to that which would be obtained from single agent oral drenches. It should be appreciated that the dosage of each agent may be varied depending on the amount of agent desired to be administered and that levels of agent above or below the example provided may be used without departing from the scope of the invention. Similarly, the dose may be varied for different animals.

According to another aspect of the present invention there is provided a method of increasing the oral bioavailability of at least one solubilisable lipophilic agent or agents in a tablet formulation characterised by the steps of:

(a) dissolving the at least one solubilisable lipophilic agent or agents in at least one solvent; and,

(b) mixing the dissolved agent or agents of step (a) with at least one co- solvent.

In addition to increasing oral bioavailability, the inventors have found that the resulting tablet formulation remains stable with minimal loss in active stability during storage. For the purposes of this specification, the term 'stable' refers to at least 6 months (preferably 18 months) chemical stability (e.g. within ±10% w/w active agent of the stated composition) of active agent when stored at 40⁰C or below and at a high humidity (relative humidity of less than 75%) and of a reasonable physical stability such that no physical alteration is observed in the tablet during storage or at the time of administration.

Other agents are also envisaged as being added to the formulation including other anthelmintic agents as well as other non-anthelmintic agents. For example, in farming applications, other nutrients such as trace minerals may be added to the formulation to allow the animal to be dosed for parasites but also to enhance the animal's nutrition.

In one embodiment mineral supplementation may be included in the formulation to provide a source of cobalt, copper, iodine, selenium and zinc.

According to a further aspect of the present invention there is provided a tablet manufactured in accordance with the method substantially as described above.

According to a further aspect of the present invention there is provided a method of treating non-human animals for parasite infestation by administration of a tablet formulation manufactured according to the method substantially as described above.

According to a further aspect of the present invention there is provided the use of at least one solubilisable lipophilic agent or agents and at least one further agent with anthelmintic activity in the manufacture of a tablet according to the method substantially as described above in the treatment of a parasite infestation in non- human animals.

Preferably, the non-human animal is a ruminant animal. In specific embodiments envisaged by the inventors, the animals are ovine or bovine species although it is anticipated that any animal susceptible to parasite infestation treatable using an anthelmintic composition may be treated.

Preferably, the parasites treated include endoparasites.

As should be appreciated by those skilled in the art, a key advantage from the formulation is that lipophilic or sparingly soluble agents may be mixed with hydrophilic agents to form combination formulations. Without the method described above, the lipophilic agent may not mix with the hydrophilic agent or on mixing, the compounds may produce unwanted reactions or degradation in agent activity.

It should further be appreciated by those skilled in the art that producing a formulation of this nature is particularly challenging. Besides the lipophilic versus hydrophilic nature of such combinations, the different agents may require very different pH ranges in order to remain stable. The present invention addresses these pH challenges by not needing to rely on pH alterations to achieve the desired oral bioavailability and stability.

A further advantage of the formulation is that, as multiple agents are included, product effectiveness is increased (several classes of parasite may be targeted in one dose) and has labour savings in terms of not having to dose two or more times with different products.

A yet further advantage of the present invention is that tablets may be advantageous in small farm applications. At present drenches and topical pour- on solutions are packaged in large containers for use in dosing large numbers of animals (typically 500 doses). The cost of these treatments is considerable. In contrast, the present invention may be sold as a package such as a bottle or box containing any number of doses which, for a small farm of lifestyle block would be preferable than purchasing a large container at significant cost. Purchase of a small number of tablets would also remove the need to dump unused drenches or pour-on solutions that have passed their expiry date.

BRIEF DESCRIPTION OF DRAWINGS

Further aspects of the present invention will become apparent from the ensuing description which is given by way of example only and with reference to the accompanying drawings in which:

Figure 1 shows a graph of levamisole blood levels measured post administration based on two formulations labelled Reformulation 1 and Reformulation 2;

Figure 2 shows a graph of abamectin blood levels measured post administration based on two formulations labelled Reformulation 1 and Reformulation 2;

Figure 3 shows a graph of albendazole sulfoxide blood levels measured post administration based on two formulations labelled Reformulation 1 and Reformulation 2;

Figure 4 shows a graph of levamisole blood levels measured post administration based on a third formulation labelled Reformulation 3 and a Reference levamisole oral drench product;

Figure 5 shows a graph of abamectin blood levels measured post administration based on a third formulation labelled Reformulation 3 and a Reference abamectin oral drench product; Figure 6 shows a graph of albendazole sulfoxide blood levels measured post administration based on a third formulation labelled Reformulation 3 and a Reference albendazole oral drench product;

Figure 7 shows a graph of levamisole blood levels measured post administration based on Reformulation 2 and a Reference levamisole oral drench product;

Figure 8 shows a graph of abamectin blood levels measured post administration based on Reformulation 2 and a Reference abamectin oral drench product;

Figure 9 shows a graph of albendazole sulfoxide blood levels measured post administration based on Reformulation 2 and a Reference albendazole oral drench product;

Figure 10 shows a graph of levamisole blood levels measured post administration based on an active only capsule with no carriers or surrounding formulation;

Figure 11 shows a graph of albendazole sulfoxide blood levels measured

V post administration based on an active only capsule with no carriers or surrounding formulation;

Figure 12 shows a graph of abamectin blood levels measured post administration of a fourth formulation (Reformulation 4) compared to a Reference abamectin oral drench;

Figure 13 shows a graph of albendazole sulfoxide blood levels measured post administration of a fourth formulation (Reformulation 4) compared to a Reference albendazole oral drench; and, Figure 14 shows a graph of levamisole blood levels measured post administration of a fourth formulation (Reformulation 4) compared to a Reference levamisole oral drench.

BEST MODES FOR CARRYING OUT THE INVENTION

Examples are how provided showing various embodiments of the present invention.

EXAMPLE 1

In a first trial, the inventors developed tablet formulations containing abamectin, albendazole and levamisole HCI and the bioavailability of these formulations was tested.

Formulations

Three formulations were tested where all three formulations were modeled on providing a tablet to treat a 60kg sheep:

• Reformulation 1 includes abamectin, levamisole HCI, and albendazole. Abamectin is dissolved in one solvent (monopropylene glycol) and includes:

Table 1 ; Reformulation 1 Com osition

Reformulation 2 includes abamectin, levamisole HCI, and albendazole. Abamectin is dissolved in two solvents (benzyl alcohol and - monopropylene glycol) and includes:

Table 2: Reformulation 2 Com osition

Reformulation 3 includes abamectin, levamisole HCI, and albendazole. Abamectin is dissolved in one solvent (monopropylene glycol) and a surfactant (sodium lauryl sulphate) and includes:

Reformulation 1 and Reformulation 2 were investigated during the first treatment session. In the second treatment session, Reformulation 3 and the Reference products (see below) were compared. The animals were then re-randomised for the third sampling session, in which Reformulation 2 was compared with the Reference products.

Animal Selection

Twelve sheep weighing 62.5 kg to 78 kg (mean = 68.6 kg) were all dosed to individual Hveweight with one anthelmintic treatment, at the standard dose rates of 0.2 mg/kg, 3.75 mg/kg and 7.5 mg/kg for abamectin, albendazole and levamisole HCI respectively.

Prior to administration of the invention or Reference formulation, all animals were dosed to their individual liveweight with Scanda™ (Batch 52888, expiry April 2006) at least 14 days prior to each treatment session, and tested free of strongylid nematodes (via faecal egg count) prior to the commencement of each treatment session.

Dosing

All sheep were administered with a dose sufficient for a 60kg animal.

Reference Products

Reference products used were single anthelmintic drenches being Valbazen™ (albendazole) (Batch 800211 , Expiry 06/2007), Genesis™ Oral Drench (abamectin) (Batch 2204, Expiry 02/2009), and Nilverm™ (levamisole) (Batch 52827, Expiry 04/2008).

It should be appreciated that such reference products provide a high bar in terms of bioavailability to be reached by the present invention. It is the inventor's experience that other liquid based multiple anthelmintic products accept a lower oral bioavailability of one or more of the agents in order to be able to combine multiple agents together. Therefore providing a multiple tablet formulation where comparable levels of bioavailability are achieved as single reference products would be an advantage. It should be noted that lower levels of bioavailability may still be of commercial value given the advantages offered by tablets and commercial activity of existing marketed multiple agent products with lower levels.

Sampling times

Blood samples (4ml per sample) were taken from the tested animals at time intervals (by active) as follows:

• Abamectin: 6 hours (h), 12h, 24h. • Albendazole: 6h, 15h, 24h

• Levamisole: 15 min, 30 min, 2h, 6h

Blood was collected from the jugular vein via venipuncture, directly into heparinised vacutainer tubes and refrigerated at 4°C until processing. It was then centrifuged at 2500 rpm for 10 minutes before the plasma was collected, and divided into test (2ml/analyte) and reserve (2ml), samples and frozen. Test and reserve samples were maintained at -18°C in separate freezers before laboratory analysis.

Results

Treatment Session 1

Levamisole

The plasma profile for levamisole from Reformulation 1 and 2 is shown in Figure 1. There appears to be a delayed absorption of the levamisole in these formulations, as the Tm_3x shown here is much later than expected. It is likely that the true C_m3x occurred between the 0.5h and 6h sampling.time, and the 6h sampling actually reflected the plasma concentration decreasing.

The results found were otherwise as expected.

Abamectin

Blood plasma levels for abamectin peaked at 4.7ng/ml and 8.5ng/ml for Reformulation 1 and Reformulation 2 respectively (Figure 2). The Tm_3x occurred 24h and 12h for the two formulations, indicating the absorption of abamectin from Reformulation 1 was also delayed.

Albendazole Parent albendazole was not detected in any of the samples at any time. The plasma profile obtained for albendazole sulfoxide (the active metabolite) is shown (Figure 3). The plasma concentrations peaked at 4.6μg/ml and 5.1 μg/ml for Reformulation 1 and Reformulation 2. The T_m3x for both formulations occurred 15h post administration.

Treatment Session 2

Levamisole

The levamisole plasma profiles obtained for Reformulation 3 and the Reference treatment groups are shown (Figure 4). The C_m3x for levamisole was 0.78μg/ml and 0.52μg/ml for Reformulation 3 and the Reference groups respectively.

This showed that the degree of absorption of levamisole from Reformulation 3 was comparable to the Reference Nilverm™ oral drench.

Abamectin

The abamectin plasma profiles observed for Reformulation 3 and the Reference products are shown (Figure 5). The C_m3x observed for the Reformulation 3 and Reference treatment groups were 1.5ng/ml and 10.2ng/ml respectively.

In this case, abamectin absorbed from Reformulation 3 was not comparable to levels observed from the Reference oral drench Genesis™.

Albendazole

The albendazole plasma profiles observed for Reformulation 3 and the Reference products are shown (Figure 6). The C_max observed for the Reformulation 3 and Reference treatment groups were 0.54μg/ml and 2.2μg/ml respectively. For both formulations T_max was 15h after administration. Reformulation 3 showed some release and absorption of albendazole but not to the extent desired to be comparable to reference oral drench product Valbazen™.

Treatment Session 3

After comparing the Reformulation 2 results from Treatment Session 1 with the Reference results from Treatment Session 2, it was decided to compare Reformulation 2 with the Reference products in a third Treatment Session (Treatment Session 3).

Levamisole

The levamisole plasma profiles observed for Reformulation 2 and the Reference products are shown (Figure 7). The C_max observed for Reformulation 2 and Reference treatment groups were 0.74μg/ml and 0.66μg/ml respectively. The Tm_ax for both formulations occurred 2h post administration, and the error bars calculated (showing standard deviations) demonstrate the variation between individuals to be greater than that resulting from the different formulations.

Therefore, Reformulation 2 compared well against the levamisole Reference oral drench product Nilverm™.

Abamectin

The abamectin plasma profiles observed for Reformulation 2 and the Reference products are shown (Figure 8). The C_m3x observed for the Reformulation 2 and Reference treatment groups were 5.8ng/ml and 11.3ng/ml respectively. The T_max for both formulations occurred 12h post administration. Whilst some effect was achieved using Reformulation 2, the bioavailability of abamectin from Reformulation 2 approximates to half that of the Reference product Genesis™. Albendazole

The albendazole plasma profiles observed for Reformulation 2 and the Reference product is shown (Figure 9). The Cm_3x observed for the Reformulation 2 and Reference treatment groups were 0.64μg/ml and 0.92μg/ml respectively. The T_max for both formulations occurred 15h post administration, and the error bars calculated (showing standard deviations) demonstrate the variation between individuals to be considerable and may largely explain the difference observed in the plasma profile of two formulations. Therefore it may be concluded that Reformulation 2 compared well against the Reference product Valbazen™.

EXAMPLE 2

Given the results in Example 1 , a further trial was completed to determine the influence of the formulation on the degree of absorption of each anthelmintic compound. This was completed by ascertaining baseline levels of drug bioavailability when animals are dosed with raw actives (no excipients).

Experimental Design

Five sheep weighing 59.0kg to 63.5kg (mean = 61.2kg) were all dosed with one anthelmintic treatment, which contained a dose sufficient for a 60kg animal at the standard dose rates of 0.2mg/kg, 3.75mg/kg and 7.5mg/kg for abamectin, albendazole and levamisole HCI respectively. The dose for each active was contained within a separate gelatine capsule.

Experimental Animals

Dosing Regime

Gelatine capsules containing a single anthelmintic drug (one capsule per sheep per drug for levamisole and abamectin, two capsules per sheep for albendazole) were used. The capsules were dark green in colour, to prevent the light sensitive abamectin from being prematurely exposed to light.

Sampling times

• Abamectin: 6h, 12h, 24h.

• Albendazole: 6h, 15h, 24h

• Levamisole: 15 min, 30 min, 2h, 6h

The blood was collected from the jugular vein via venipuncture, directly into heparinised vacutainer tubes and refrigerated at 4°C until processing. It was then centrifuged at 2500 rpm for 10 minutes before the plasma was collected, and divided into test (2ml/analyte) and reserve (2ml), samples and frozen. Test and reserve samples were maintained at -18°C in separate freezers before laboratory analysis.

Results

Abamectin Blood plasma levels for abamectin peaked just above the detection threshold indicating that abamectin was not absorbed.

The minimal levels of abamectin absorbed are not surprising considering that this drug is lipophilic and usually formulated as a solution. Therefore, it is expected to require excipients to facilitate bioavailability of this drug.

Levamisole

The plasma profile for levamisole is shown in Figure 10. The Tm_3x shown here is later than predicted by publications, but consistent with previous studies by the inventor's. It is envisaged that this is because the drugs were all administered in a gelatine capsule, and this would have taken several minutes to break down, which may have delayed the release of the levamisole to the rumen. The C_n^_x was approximately 50% of that generally considered necessary for full therapeutic efficacy.

The plasma profile for levamisole was similar to that observed in previous studies, suggesting that formulations do not cause delayed absorption of the drug as previously thought. Rather, this delay may be due to the active passing through the mucosal layer between the gut and bloodstream.

Albendazole

This data indicates that T_max for albendazole sulfoxide occurred between the 6h and 15h sampling times (Figure 11). However, C_m3x was approximately 50% of that generally considered necessary for full therapeutic efficacy.

The low bioavailability of albendazole was surprising, as this drug is usually formulated as a suspension, with the majority of excipients being included as aids keeping the drug in suspension and not necessarily to assist in bioavailability. The formulation in tablet usage appears to have an effect on albendazole bioavailability.

Conclusions

The results from this study (when compared to Reference products) suggest that the inclusion of exdpients in anthelmintic formulations improves the bioavailability of each of the three drugs discussed here. In the absence of excipients, plasma levels obtained for albendazole and levamisole were reduced (compared to reference products), but comparable to previous test formulations tested.

Plasma concentrations of abamectin were lower than those obtained previously for example that shown in Example 1.

The results show that tablet formulations (containing excipients) are an important factor in achieving drug bioavailability.

EXAMPLE 3

A fresh formulation (Reformulation 4) was tested based on prior trials including those identified above in Examples 1.

The formulation included abamectin, albendazole and levamisole. The abamectin was dissolved and mixed with two organic solvents during manufacturing (benzyl alcohol and monopropylene glycol). More specifically, the formulation was as follows:

Table 4: Reformulation 4 Composition

The above ingredients were used to manufacture Reformulation 4 as follows:

1. Dissolve the abamectin in benzyl alcohol

2. Mix with monopropyiene glycol

3. Mix with levamisole, albendazole, polyvinyl pyrrolidone and corn starch

4. Dry the mixture at 40⁰C

5. Mix the dried mixture with sodium starch glycolate, aerosil 200 and magnesium stearate

6. Press into a tablet

The finished product is a tablet of an approximately 21mm diameter that breaks down within approximately 15 minutes in 37°C water. During storage, the tablet remains stable and active agent levels remain stable.

In this example, the animals used were cattle with other characteristics of the study remaining the same as in Example 1 except that the formulation was altered by doubling the amount of albendazole to provide an equivalent dose rate as reference treatments.

Results

Abamectin

Abamectin is lipophilic and requires formulation in order for the abamectin to be absorbed. The formulation was altered to increase this absorption by dissolving and mixing the abamectin with solvents. In addition, the dosage of abamectin was approximately doubled in order to achieve a comparable result to the Reference product. Increasing the dose for abamectin is standard practice when designing cattle formulations as sheep have a greater absorption, distribution, metabolism and excretion (ADME) profile than cattle.

As can be seen in Figure 12, Reformulation 4 resulted in the abamectin profile becoming almost equivalent with that observed from the Reference oral drench formulation Genesis™.

Albendazole

For albendazole, the amount of albendazole used was approximately doubled in order to ensure the preferred cattle dose level was achieved.

As can be seen in Figure 13, Reformulation 4 resulted in the albendazole profile also becoming almost equivalent with that observed for the Reference oral drench formulation Valbazen™.

Levamisole

Minimal changes were made to levamisole handling and amount in Reformulation 4 compared to Example 1 as the dose of levamisole was already comparable to the Reference product in earlier tests.

As can be seen in Figure 14, Reformulation 4 resulted in the levamisole profile also becoming almost equivalent with that observed for the Reference oral drench formulation Nilverm™.

EΞXAMPLE 4

Two further trials were completed to test the storage stability of the tablets formed from the above methods over time. The trials were conducted using tablets termed Reformulation 2 described above. In the trials, a total of 24 tablets were initially tested for:

• General visual description

• Disintegration time

• Average weight

• Weight variation

• Concentration of abamectin

• Hardness

Subsequent to initial tests, a first trial was commenced with 12 tablets placed into an environment held at a constant temperature of 30⁰C and 60% relative humidity.

A second trial was also commenced with 12 tablets placed into an environment held at a constant temperature if 40⁰C and 75% relative humidity. The above temperatures and humidity's were chosen as being trying' conditions in which the tablets might be stored and represent worst case scenarios where deterioration might occur.

The first trial was conducted over 18 months and the second trial over 6 months.

At time intervals noted in Tables 5 and 6 below, the tablets were tested using the same tests as that completed during the initial test and the results compared. Where there were no variations to initial results, the stored tablet was said to

'comply'.

Table 5: Storage Stability for a Temperature of 30⁰C and Relative Humidit of 60%

Table 6: Storage Stability for a Temperature of 40⁰C and

Relative Humidit of 75%

The above trials showed that the tablet product was remarkably stable and did not breakdown under trying conditions in terms of temperature and humidity over significant time periods.

EXAMPLE 5

The tablet formulations described above were manufactured as described and packaged in a blister pack sealing the tablets into a package. Markings may be included on the packaging indicating the user when the tablets should be administered and any dosing instructions such as how to use an applicator device such as a pill popper device.

The blister pack is attached to a pill applicator device or composition and placed into a package for sale jointly as a kit.

Besides mechanical devices for administration such as a pill popper of gas actuated applicator, the applicator may be replaced by an administration/swallowing-enhancing coating such as a dough composition which encases the pill and which masks the pill from the animal. For convenience, a disposable applicator is preferred.

As should be appreciated the kit may contain as little as one dose or many thousands of doses as may be required.

Tablets may be supplied with or without an applicator.

EXAMPLES CONCLUSION

It should be appreciated from the above examples that developing a tablet for delivery of two or more anthelmintic agents including abamectin and albendazole has presented many challenges. The inventors have achieved this providing a formulation including multiple actives that not only provides agents in a state able to be absorbed, but also in a state the may be absorbed at comparable levels to that achieved using other methods of administration such as oral drenches.

It should be appreciated that as ivermectin has similar lipophilic properties as abamectin, similar results may be achieved if ivermectin were used. In addition, similar results may also be expected for other benzimidazole compounds based on results found for albendazole.

An advantage of tablets is that they provide a fixed and known dose of agent and there is no need to dilute, measure out and use specialised equipment such as drench guns. In addition, tablets may easily be sold in large or small numbers

< whereas oral drenches for example are only sold in large volumes (and at greater expense).

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof as defined in the appended claims.

Claims

WHAT WE CLAUVUS:

1. A method of manufacturing a tablet formulated for administration to an animal containing at least one macrocyclic lactone compound and at least one additional compound with anthelmintic activity by the steps of:

(a) dissolving the macrocyclic lactone compound or compounds in at least one organic solvent;

(b) combining the mixture of step (a) with at least one organic co- solvent;

(c) combining the mixture of step (b) with:

i. at least one additional compound with anthelmintic activity;

ii. at least one binder compound;

iii. at least one filler / bulking agent compound; and,

(d) drying the mixture of step (c).

2. The method of claim 1 wherein the macrocyclic lactone compound or compounds are characterised by having poor solubility and/or dispersion characteristics in an aqueous environment.

3. The method as claimed in claim 2 wherein the aqueous environment is extracellular fluid.

4. The method as claimed in any one of claims 1 to 3 wherein the method includes a further step (e) after step (d) of:

5. The method as claimed in any one of the above claims wherein the final mixture is compressed into a tablet.

6. The method as claimed in any one of the above claims wherein the macrocyclic lactone compound is abamectin or ivermectin.

7. The method as claimed in any one of the above claims wherein the macrocyclic lactone compound or compounds included in the tablet are at a dose sufficient to: prevent growth of parasites; reduce parasite numbers; kill parasites; kill incoming parasite larvae; lower the number of surviving incoming parasite larvae; kill or reduce the number of hypobiotic state parasites; and combinations thereof.

8. The method as claimed in any one of claims 1 to 6 wherein the macrocyclic lactone compound or compounds included in the tablet are at a concentration sufficient to provide the animal with a dose of the compound or compounds to the animal equivalent to that which would be obtained from an oral drench containing the same lipophilic compound or compounds.

9. The method as claimed in any one of the above claims wherein the macrocyclic lactone compound is abamectin included at a rate of 0.2mg to 0.6 mg of abamectin per kg of animal body weight.

10. The method as claimed in any one of the above claims wherein the macrocyclic lactone compound is abamectin included at a rate of 0.4mg of abamectin per kg of animal body weight.

11. The method as claimed in any one of claims 1 to 8 wherein the macrocyclic lactone compound is ivermectin included at a rate of 0.2mg to ύ.6mg of ivermectin per kg of animal body weight.

12. The method as claim in any one of claims 1 to 8 wherein the macrocyclic lactone compound is ivermectin included at a rate of 0.4mg of ivermectin per kg of animal body weight.

13. The method as claimed in any one of the above claims wherein the macrocyclic lactone compound is formulated to be rapidly released on oral administration.

14. The method as claimed in any one of the above claims wherein the macrocyclic lactone compound or compounds are formulated so that the compound or compounds remain present in the bloodstream of the animal for at least 24 hours.

15. The method as claimed in any one of the above claims wherein the macrocyclic lactone compound or compounds are formulated so that the compound or compounds dissipate from the bloodstream within two weeks.

16. The method as claimed in any one of the above claims wherein the additional compound or compounds with anthelmintic activity added in step (c) are compounds with a different spectrum of anthelmintic activity to the macrocyclic lactone compound used in step (a).

17. The method as claimed in any one of the above claims wherein the anthelmintic compound added at step (c) is a substituted or unsubstituted benzimidazole compound.

18. The method as claimed in claim 17 wherein the substituted or unsubstituted benzimidazole compound has the structure:

where n = 1 or 2;

where Ri which may be the same or different at each occurrence = H, Cl, -SC₃H₇, -SOC₃H₇, -SC₆H₅, -SOC₆H₅, -C₄H₉, Or-OC₆H₃CI₂; and,

where R₂ = -NHCO₂CH₃ or -SCH₃.

19. The method as claimed in claim 17 or claim 18 wherein the benzimidazole compound or compounds are selected from: albendazole, ricobendazole, fenbendazole, oxfenbendazole, parbendazole, triclabendazole and combinations, analogues and derivatives thereof.

20. The method as claimed in claim 18 or claim 20 wherein the benzimidazole compound is albendazole.

21. The method as claimed in any one of claims 17 to 20 wherein the benzimidazole compound or compounds included in the tablet are at a concentration sufficient to provide the animal with a dose of the compound or compounds at a level sufficient to: prevent growth of parasites; reduce adult parasite numbers; kill adult parasites; and combinations thereof.

22. The method as claimed in any one of claims 17 to 20 wherein the benzimidazole compound or compounds included in the tablet are at a concentration sufficient to provide the animal with a dose of the compound or compounds to the animal equivalent to that which would be obtained from, an oral drench containing the same benzimidazole compound or compounds.

23. The method as claimed in any one of claims 15 to 18 wherein the benzimidazole compound is albendazole included at a rate of at least 1 mg of albendazole per kg of animal body weight.

24. The method as claimed in any one of claims 17 to 22 wherein the benzimidazole compound is albendazole included at a rate of at least 3.7 mg of albendazole per kg of animal body weight wherein the animal is a sheep.

25. The method as claimed in any one of claims 17 to 23 wherein the benzimidazole compound is albendazole included at a rate of at least 7.5 mg of albendazole per kg of animal body weight wherein the animal is a bovine species.

26. The method as claimed in any one of the above claims wherein the benzimidazole compound or compounds are formulated to be rapidly released on oral administration.

27. The method as claimed in any one of the above claims wherein the benzimidazole compound or compounds are formulated so that the compound or compounds or its active metabolites remain present in the bloodstream of the animal for at least 12 hours.

28. The method as claimed in any one of the above claims wherein the benzimidazole compound or compounds are formulated so that the compound or compounds or its active metabolites dissipate from the bloodstream within 4 days.

29. The method as claimed in any one of claims 17 to 28 wherein the benzimidazole raw material is a dry micronised particulate powder

30. The method as claimed in any one of claims 1 to 16 wherein the additional anthelmintic compound added to the mixture in step (c) is levamisole.

31. The method as claimed in claim 30 wherein the levamisole is levamisole hydrochloride (HCI) included at a rate of approximately 5 to 9 mg levamisole per kg of animal body weight.

32. The method as claimed in any one of claims 1 to 16 wherein both a substituted or unsubsfrtuted benzimidazole compound and levamisole compound are added in step (c).

33.. The method as claimed in any one of the above claims wherein the solvent or solvents and co-solvent or co-solvents are different compounds.

34. The method as claimed in any one of the above claims wherein the organic solvent or solvents are selected from: an alcohol, a glycol, an ether, pyrrolidone compounds with two or more carbon atoms, and combinations thereof.

35 The method as claimed in any one of the above claims wherein the organic solvent is selected from: ethyl alcohol; benzyl alcohol; phenethyl alcohol; ethyl benzyl alcohol; glycols; glycol ethers; glycol ether acetates; C₁ to C₈ alkyl pyrrolidones; and combinations thereof.

36. The method as claimed in any one of the above claims wherein the solvent is benzyl alcohol.

37. The method as claimed in any one of the above claims wherein the co- solvent or co-solvents are alcohol or ether compounds with three or more carbon atoms.

38. The method as claimed in any one of the above claims wherein the co- solvent or co-solvents are selected from: diol alcohols including glycols; aromatic monohydric alcohols; glycol ethers; glycol ether acetates; and combinations thereof.

39. The method as claimed in any one of the above claims wherein the co- solvent is a propylene glycol compound.

40. The method as claimed in any one of the above claims wherein the co- solvent is monopropylene glycol.

41. The method as claimed in any one of the above claims wherein the binder is a pyrrolidone compound.

42. The method as claimed in any one of the above claims wherein the binder in step (c) is a polyvinyl pyrrolidone compound.

43. The method as claimed in any one of the above claims wherein the filler, disintegrant, glidant/free flowing agent and lubricant used in step (c) include: corn starch, sodium starch glycolate, silica or silica based compositions, magnesium stearate or other anionic salts.

44. The method as claimed in claim 4 wherein the filler, disintegrant, glidant/free flowing agent and lubricant used in step (e) includes: corn starch, sodium starch glycolate, silica or silica based compositions, magnesium stearate or other anionic salts.

45. The method as claimed in any one of the above claims wherein drying in step (d) is completed by air drying at 40⁰C.

46. The method as claimed in any one of the above claims wherein the tablet produced by the method disintegrates within approximately 15 minutes when placed in water at 37°C.

47. A method of increasing the bioavailability of at least one macrocyclic lactone compound or compounds in a tablet formulation characterised by the steps of:

(a) dissolving the at least one macrocyclic lactone compound or compounds in at least one solvent; and,

(b) mixing the dissolved compoundor compounds of step (a) with at least one co-solvent.

48. The method of claim 47 wherein the solvent is selected from: an alcohol a glycol, an ether, a pyrrolidone compound with two or more carbon atoms, and combinations thereof.

49. . The method as claimed in claim 47 wherein the co-solvent is an alcohol or ether compound with three or more carbon atoms.

50. The method as claimed in claim 47 wherein the solvent(s) and co- solvents) used are different compounds.

51. The method as claimed in any one of the above claims wherein the tablet remains stable with a less than 10%.w/w loss in active concentration during storage for at least 6 months at a temperature of less than 40⁰C and relative humidity of less than 75%.

52. The method as claimed in claim 51 wherein the tablet remains stable for at least 9 months.

53. The method as claimed in claim 51 or claim 52 wherein the tablet is chemically stable whereby the active compound concentration remains at within 10% of initial levels and is physically stable such that no physical alteration is observed in the tablet during storage or at the time of administration.

54. The method as claimed in any one of the above claims wherein the tablet contains mineral sources selected from: cobalt, copper, iodine, selenium, zinc and combinations thereof.

55. A tablet manufactured in accordance with the method as claimed in any one of claims 1 to 52.

56. A method of treating non-human animals for parasite infestation by administration of a tablet formulation manufactured according to the method as claimed in any one of claims 1 to 54.

57. The method as claimed in claim 56 wherein the non-human animal is a ruminant animal.

58. The method as claimed in claim 56 or claim 57 wherein the non-human animal is of ovine or bovine species.

59. The method as claimed in any one of claims 56 to 58 wherein the parasites are endoparasites.

60. Use of at least one macrocyclic lactone compound or compounds and at least one further agent with anthelmintic activity in the manufacture of a tablet according to the method as claimed in any one of claims 1 to 54 in the treatment of a parasite infestation in non-human animals.

61. The use as claimed in claim 60 wherein the non-human animal is a ruminant animai.

62. The use as claimed in claim 60 or claim 61 wherein the non-human animal is of ovine or bovine species.

63. The use as claimed in any one of claims 60 to 62 wherein the parasites are endoparasites.

64. A method, substantially as hereinbefore described with reference to Example 1 and Reformulation 2 as well as Figure 3.

65. A method, substantially as hereinbefore described with reference to Example 3 and Reformulation 4 as well as Figure 4: