WO1988007852A1

WO1988007852A1 - Liposome entrapped magnesium

Info

Publication number: WO1988007852A1
Application number: PCT/US1988/001006
Authority: WO
Inventors: Alan I. Faden
Original assignee: Innovative Therapeutics Corporation
Priority date: 1987-04-06
Filing date: 1988-04-05
Publication date: 1988-10-20

Abstract

A dosage unit suitable for intravenous, intramuscular or subcutaneous injection which contains an effective amount of magnesium compound contained in positively charged, unilamellar liposomes capable of releasing said magnesium and a pharmaceutically acceptable solution is disclosed. Compositions containing the liposome entrapped magnesium compound and methods of treating traumatic injuries and inducing calcium channel antagonistic activity through the administration of the liposome entrapped magnesium compound are also discussed.

Description

LIPOSOME ENTRAPPED MAGNESIUM BACKGROUND OF THE INVENTION It has been discovered that free intracellular levels of magnesium are rapidly depleted following traumatic brain or spinal cord injuries. Severity of the depletion can be correlated with the severity of the injury. Thus, methods of reversing the depletion of magnesium were investigated. DETAILED DESCRIPTION OF THE INVENTION It was discovered that magnesium infusions following traumatic injuries protect against the worsening of the injury by magnesium depletion, and improve the prognosis of traumatically injured animals. However, cations such as magnesium do not readily permeate the central nervous system. Consequently, the dosages required for systemic administration of magnesium are so high that the potential exists for undesirable side effects such as respiratory suppression and hypotension. These side effects would limit the therapeutic value of the magnesium treatment. Further, it has been shown that magnesium may serve as a calcium channel antagonist in central nervous system and non-central nervous system ailments.

Liposome entrapment has been proposed as a possible route to increase the biological halflives of certain pharmaceuticals and enhance transport into various cells and across the blood-brain barrier. The present invention describes the use of liposome entrapped magnesium to permit effective treatment at lower dosage levels than systemic administration of the cation.

In a first aspect of this invention there is provided a dosage unit suitable for intravenous, intramuscular or subcutaneous injection which comprises (i) an effective amount of magnesium compound contained in positively charged, unilamellar liposomes capable of releasing said magnesium; and (ii) a pharmaceutically acceptable solution, said effective amount being sufficient to transport a pharmaceutically effective amount of magnesium to a cell site.

The magnesium compound is contained in positively charged, unilamellar liposomes, which are capable of releasing said magnesium. Typically, there is a plurality of liposomes, each containing a magnesium compound. As a pharmaceutically acceptable solution there is contemplated any solution that is safe for injection and that is biologically inert, and hence does not interfere with the active ingredient. As such pharmaceutically acceptable solutions may .be mentioned an isotonic solution suitable fox injection into a patient. The isotonic solution may contain water, salt, and conventional ingredients such a glucose. As a pharmaceutically effective amount of magnesium to be transported to a cell site, there may be mentioned a concentration of magnesium in the injection fluid from about 0.05 to 50 m oles per milliliter. A preferred embodiment of this aspect provides a concentration of 0.5 to 5 mmoles per milliliter of the , _injectable dosage" form. The preferred active ingredient dosage is most conveniently provided through injections of 1 - 10 cc of the injectable dosage form.

In addition to the injectable dosage forms discussed above, the active ingredient of the present invention is capable of being administered in any manner which will allow,the liposome entrapped -magnesium to enter the blood stream without substantial degradation. Thus, other administration routes such as oral administration are also contemplated by the present invention. A positively charged, unilamellar liposome useful in the

..'present invention- is prepared in accordance with a method described by Szoka et al. PNAS. 75: 4194-4198 (1978).

The lipids containing L-alpha-di almitoy1 phosphatidylcholine, cholesterol and sterylamine in a molar ratio of 14:7:4 are dissolved in chloroform. Ether and a phosphate buffer are then added. The admixture undergoes sonication followed by solvent removal and resuspension in a phosphate buffer. Liposomes, thus prepared, ar then used in an entrapment procedure analogous to that of Ki elberg et al., Life Sciences, V. 17, pp. 715-724 (1975) for the entrapment of potassium and sodium, wherein the magnesium component of the active ingredient is suspended in a phosphate buffer. The two solutions are admixed and subjected to sonication. Then the solvent is removed and the liposome entrapped magnesium results.

A second aspect of the present invention provides a method of preventing magnesium depletion in a patient suffering from traumatic brain or spinal injuries which comprises administering magnesium into the bloodstream surrounded by positively charged, unilamellar liposomes. This is, the active ingredient of the present invention can be used in the treatment of traumatic injuries to the brain and spinal cord. As an effective treatment protocol for traumatic injury, there may be mentioned the administration to a patient of a dosage of active ingredient in the range of 0.5 to 5 mmoles, injected 3 times daily.

A further aspect of the present invention provides a method of inducing calcium channel antagonist activity in a patient suffering from ailments which require such activity which comprises administration to said patient of an effective amount of magnesium compound contained in positively charged, unilamellar liposomes capable of releasing said magnesium.

That is, the active ingredient of the present invention can be used in a method for treating ailments which require induction of calcium channel antagonists activity in a patient. For example, the active ingredient of present invention is -useful in control of vasospasm. Thus, treatment of ailments such as vascular headaches (migraines) , subarachnoid hemorrhages and ischemic brain injury resulting from stroke or cardiac arrest are contemplated by the present invention. As an effective ^•treatment protocol for such ^* ailments, there may be mentioned the administration to a patient of a dosage of active ingredient in the range of 0.5 - 10.0 mmoles injected 1-3 times daily. Also, diseases such as epilepsy in which calcium accumulation may be a problem, can be treated by the liposome entrapped magnesium of the present invention. Treatment of certain alcohol withdrawal syndromes is also contemplated by the.present invention. A final aspect of the present invention provides a composition comprising a plurality of positively charged, unilamellar liposomes surrounding a magnesium compound, said composition being suitable for in vivo transport of magnesium to cell sites. In a preferred embodiment of this aspect the entrapped magnesium .compound is selected from the group comprising magnesium chloride or magnesium sulfate. In another preferred embodiment of this aspect the positively charged, unilamellar liposome is a made up of positively charged lipid or lipid-like compounds or a combination of a plurality of the lipid or lipid-like compounds. In -.more preferred embodiment the positively charged, unilamellar liposome is a mixture of L-alpha- dipalmitoyl phosphatidylcholine, cholesterol and sterylamine. In a still more preferred embodiment the positively charged, unilamellar liposome comprises L-alpha- dipalmitoyl phosphatidylcholine, cholesterol and sterylamine in a molar ratio of 14:7:4. The liposomes are prepared by the ;method of Szoka et al. (PNAS, 1978) and liposome-entrapped magnesium prepared as provisions described for sodium and potassium by Kimelberg et al. (Life Sciences) V. 17, pp. 715-724, 1975.

EXAMPLE 1 The positively charged, unilamellar liposome portion of the present invention is produced by the method of Szoka et al. Then MgCl₂ is entrapped through a process analogous to that of Kimelberg et al.

EXAMPLE 2 A liposome entrapped magnesium is produced in the same manner as Example 1 except that MgS0₄ is entrapped.

EXAMPLE 3 The liposome entrapped magnesium of Example 1 is admixed with isotonic solution to obtain a final concentration of active ingredient in the solution of 5.0 mmoles/cc. EXAMPLE 4

The liposome entrapped magnesium of Example 2 is admixed with isotonic solution to obtain a final concentration of active ingredient in the solution of 1.0 mmoles/cc.

EXAMPLE 5 Treatment of a patient suffering from a traumatic injury is accomplished through injection of 10 cc of the pharmaceutical preparation of Example 3.

EXAMPLE 6 Treatment of a patient suffering from an ischemic injury is accomplished through injection of 5 cc of the pharmaceutical preparation of Example 3.

EXAMPLE 7 Treatment of a patient suffering from a traumatic injury is accomplished through injection of 5 cc of the pharmaceutical preparation of Example 4.

EXAMPLE 8 Treatment of a patient suffering from an ischemic injury is accomplished through injection of 15 cc of the pharmaceutical preparation of Example 4. EXAMPLE 8 Treatment of a patient in need of a calcium channel antagonist is accomplished through injection of 2.5 cc of the pharmaceutical preparation of Example 4.

Claims

WHAT IS CLAIMED IS:

1. A dosage unit suitable for intravenous, intramuscular or subcutaneous injection which comprises (i) an effective amount of magnesium compound contained in positively charged, unilamellar liposomes capable of releasing said magnesium; and (ii) a pharmaceutically acceptable solution, said effective amount being sufficient to transport a pharmaceutically effective amount of magnesium to a cell site.

2. A dosage unit suitable for intravenous, intramuscular or subcutaneous injection of claim 2 wherein said effective amount of magnesium is from about 0.5 to about 5 mmoles per mililiter.

3. A method of preventing magnesium depletion in a patient suffering from traumatic brain or spinal injuries or which comprises administering magnesium into the bloodstream in the dosage form of claim 1 containing positively charged, unilamellar liposomes.

4. A method inducing calcium channel antagonist activity in a patient suffering from ailments which require such activity which comprises administration to said patient of an effective amount of magnesium compound contained in positively charged, unilamellar liposomes capable of releasing said magnesium.

5. A composition comprising a plurality of positively charged, unilamellar liposomes surrounding a magnesium compound, said composition being suitable for in vivo transport of magnesium to cell sites.

6. A composition of claim 5 wherein said magnesium compound is magnesium chloride or magnesium sulfate.

7. A composition of claim 5 wherein said positively charged, unilamellar liposome is a mixture of L-alpha- dipalmitoyl phosphatidylcholine, cholesterol and sterylamine.