CA2009307A1 - Process for the preparation of aqueous mixed micelle solutions - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A process for the preparation of aqueous mixed micelle solutions containing mixed micelles formed from lipoids and salts of bile acids wherein active agents which are sparingly soluble or insoluble in water are optionally solubilized, characterized by suspending the free bile acids at a temperature of 40°C to 100°C in an aqueous solution containing, if desired, isotonizing additives and/or water-soluble active agents, dispersing the lipoids at a temperature of 40°C to 100°C in this suspension, and neutralizing the resultant dispersion with bases at a temperature of 0°C to 100°C, with the proviso that optionally the active agents sparingly soluble or insoluble in water are dispersed together with the lipoids or are solubilized in the mixed micelle solution which does not contain these active agents.

Description

29~ 7 PROCESS FOR T~IE PREPARATION OF
AQUEOUS MIXED MICELLE SOLUTIONS

Backaround of th~ Invention The invention relates to a process for the preparation of aqueous mixed micelle solutions containing mixed micelles formed from lipoids and salts of bile acids wherein active agents which are sparingly soluble or insoluble in water are optionally solubilized.
Processes for the preparation of such mixed micelle solutions have been known, for example, from German Patent 27 30 570.
In the conventional processes, the mixed micelle solucions are prepared by dissolving the lipoids, the salts of the bile acids, and optionally the active agents ` 15 which are sparingly soluble or insoluble in water, in an organic solvent (e.g., ethanol), and concentrating the solutions so that a lipid film is formed on the walls of the vessels, this film being detached by means of aqueous solutions (Biochemistry 19:602 et seq. and 615 et seq., ' 20 1980; Naturforsch. [Natural Sciences Research] 32c:748 et seq., 1977).
However, this procedure is rather expensive and can be transposed into an industrially useful scale only with considerable expenditure in apparatus.
Besides this preferred method, a process has been known, for instance, from Example 3 of the aforementioned Patent 27 30 570 wherein such mixed micelle solutions are produced by mixing the components and agitation of the mixture.
However, this process not only exhibits the drawback that it takes several daysj but it is also found, when ~! ~
, r ~ cating this example -- without the ~ctive agent --. ~

.
~ .

- 2 - ~ i7 that only strongly clouded solutions are obtained in this way containing mixed micelles having an average diameter of about 340 nm.
Clear solutions with mixed micelles having an average diameter of about 10 nm cannot be obtained in this way.

Summary of the Invention It has now been found that it is possible to produce, in a simple way and within a short period of time, such clear, aqueous solutions of mixed micelles with the aid of a process characterized by suspending the free bile acids at a temperature of 40C to 100C in an aqueous solution containing, if desired, isotonizing additives and/or water soluble active agents, dispersing the lipoids at a temperature of 40C to 100C in this suspension, and neutralizing the resultant dispersion at a temperature of 0C to 100C with bases, with the proviso that optionally the active agents sparingly soluble or insoluble in water are dispersed together with the lipoids or are solubilized in the mixed micelle solution which does not contain these active agents.
The process according to the invention can be performed by using the same bile acids as do the previously known methods. Suitable bile acids are 5~-cholan-24-oic acid derivatives of the general formula ~: ,~c~

` 1 ,1 1 - ~\ ~ y "~.~2 Ho , -- , :, .
-, , _ 3 _ 2 wherein R1 and Rz, as well as R3 and R4 jointly mean an oxo group, two hydrogen atoms, or a hydrogen atom and a hydroxy group, and X is a hydroxy group or a grouping of tne for~ula -NH-CH2-CO2H or -NH-(CH2)2-so3H.
Suitable bile acids that can be cited as examples include cholic acid, glycocholic acid, taurocholic acid, deoxycholic acid, glycodeoxycholic acid, taurodeoxycholic acid, chenodeoxycholic acid, glycochenodeoxycholic acid, and taurochenodeoxycholic acid.
Preferably, 1-30 g and especially 2-15 g of bile acid is utilized per 100 g of the aqueous solution optionally containing isotonizing additives and water-soluble active agents, in order to prepare the aqueous mixed micelle solution.
For preparing the aqueous mixed micelle solutions, the same lipoids as in the conventional methods can be utilized in the process according to this invention.
Suitable lipoids include, for example, ; monoglycerides, sulfatides, and especially phospholipids, such as the sphingomyelins, the plasmalogens, the phosphatidyl cholines, the phosphatidyl ethanolamines, the phosphatidyl serines, the phosphatidyl inositols, and the cardiolipins, also mixtures of these lipoids (Dr.
; Otto-Albrecht Neumuller, Rompps Chemie-Lexikon [Rompp's Chemical Dictionary], Franckh'sche Verlagshandlung, Stuttgart, Germany, 2665, 3159, 3920 and 4045).
Preferably, 3-40% and especially 5-20% o~ lipoid per 100 g of the aqueous solution, optionally containing isotonizing additives and/or water-soluble active agents, is utilized for preparing the aqueous mixed micelle solutions. The weight ratio of lipoid to bile acid is preferably 0.1:1 to 2:1, and is particularly 0.8:1 to 2:1.
.

2~ 3~7 Suitable bases ~or preparing the aqueous mixed micelle solutions according to the process of this invention include alkali hydroxides, such as lithium hydroxide, potassium hydroxide and especially also sodium hydroxide, and organic nitrogen bases which form physiologically acceptable salts. Such nitrogen bases include, for example, ammonia, primary, secondary or tertiary amines, ethanolamine, diethanolamine, piperazine, morpholine, lysine, ornithine, arginine, N, N-dimethylglucamine, choline, and particularly N-methylglucamine and tris(hydroxymethyl)aminomethane.
Suitable active agents sparingly soluble or insoluble in water are preferably those having a solubility in water at room temperature not exceeding 2%.
Such active agents include, for example, plant-protective agents, such as poorly soluble insecticides or herbicides and, especially, poorly soluble pharmaceutically active compounds.
Pharmaceutically active compounds of poor solubility or insoluble in water pertaining to the following active agent groups are suitable, for example, to prepare the medicinal agents according to this invention:
Gestagenically active steroid hormones, such as, for example, 13-ethyl-17~-hydroxy-18,19-dinor-17~-pregn-4-2S en-20-yl-3-one (= levonorgestrel); 13-ethyl-17~-hydroxy-; 18,19-dinor-17~-pregna-4,15-dien-20-yn-3-one (= gestodene); or 13-ethyl-17~-hydroxy-11-methylene-18,19-dinor-17~-pregn-4-en-20-yn (desorgestrel);
estrogenically active steroid hormones, such as 3-hydroxy-1,3,5(10)-estratrien-17-one (= estrone) or 19-nor-17~-pregna-1,3,5(10)-trien-20-yne-3,17~-diol (ethynylestradiol).
Androgenically active steroid hormones, such as 17~-hydroxy-4-androsten-3-one (= testosterone) and its esters, and 17~-hydroxy-1~-methyl-5~-androstan-3-one (= mesterolone).

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- 5 ~ 7 Antiandrogenically active steroid hormones, such as 17~-acetoxy-6-chloro-1~,2B-dihydro-3'H-cyclo-propa[l,2]pregna-1,4,6-triene-3,20-dione (cyproterone acetate).
Corticoids, such as llB,17~,21-trihydroxy-4-pregnene-3,20-dione (= hydrocortisone); 11~,17~,21-trihydroxy-1,4-pregnadiene-3,20-dione (= prednisolone);
llB,17~,21-trihydroxy-6~-methyl-1,4-pregnadiene-3,20-dione (= methylprednisolone); and 6~,9~-difluoro-llB,21-dihydroxy-16~-methyl-1,4-pregnadiene-3,20-dione (= diflucortolone).
Ergolines, such as 3-(9,10-dihydro-6-methyl-8~-ergolinyl)-l,1-diethylurea (= ergoline); 3-(2-bromo-9,10-dihydro-6-methyl-8~-ergolinyl)-1,1-diethylurea (= bromergoline); or 3-(6-methyl-8~-ergolinyl~-1,1-diethylurea (= terguride).
Antihypertensive agents, such as 7~-acetylthio-17~-hydroxy-3-oxo-4-pregnene-21-carboxylic acid ~-lactone (= spironolactone), or 7~-acetylthio-15B,16~-methylene-3-oxo-17~-pregna-1,4-diene-21,17-carbolactone (= mespirenone).
Anticoagulants, such as 5-[hexahydro-5-hydroxy-4-(3-hydroxy-4-methyl-1-octen-6-ynyl)-2(lH)-pentalenyl-idene)]pentanoic acid (= iloprost).
Psychopharmaceuticals, such as 4-(3-~yclopentyl-oxy-4-methoxyphenyl)-2-pyrrolidone (= rolipram) and 7-chloro-l t 3-dihydro-1-methyl-5-phenyl-2H-1,4-benzo-diazepin-2-one (= diazepam).
Carotenoids, such as ~-carotene and B-carotene.
Fat-soluble vitamins, such as vitamins of the vitamin A, vitamin D, vitamin E and vitamin K groups.
An especially preferred group is constituted by the B-carbolines as disclosed, for example, in European Patent Applications 234,173 and 239,667. Nonlimiting examples of B-carbolines include the isopropyl ester of 6-benzoyloxy-4-methoxymethyl-~-carboline-3-carboxylic . ~

: , .

2~ 3~

acid (= becarnil); the isopropyl ester of 5~
chlorophenoxy)-4-methoxymethyl-~-carboline-3-carboxylic acid (= Cl-PHOCIP); the ethyl ester of S-isopropoxy-4-methyl-~-carboline-3-carboxylic acid (= IPMCE); and 5-(4-chlorophenoxy)-3-(3-ethyl-1,2,4-oxadiazol-5-yl)-4-methoxymethyl-~-carboline (= Phoco). The optimum active agent concentration in the mixed micelle solutions is, of course, dependent on the structure of the active agent and must be determined by means of the conventional preliminary tests. Generally, the concentration of ~-carbolines is 1 ~g to 40 mg and preferably 100 ~g to lO
mg of active agent per ml of mixed micelle solution.
Preferably, glycocholic acid and phospholipids are utilized for preparing the mixed micelles proper.
The aqueous mixed micelle solutions prepared according to the process of this invention can contain isotonic additives, if desired, in order to raise their osmotic pressure. Suitable additives include, for example, inorganic or organic salts or buffers, such as sodium chloride, phosphate buffer, citrate buffer, glycine buffer, citrate-phosphate buffer, maleate buffer, etc.; mono- or disaccharides, such as glucose, lactose, sucrose; sugar alcohols, such as mannitol, sorbitol, xylitol, or glycerol; or water-soluble polymers, such as dextran or polyethylene glycol.
These isotonizing materials are customarily used in such concentrations that the resultant aqueous mixed micelle solution exhibits an osmotic pressure of 5-100 mosm -- in case of injection solutions, optimally about 300 mosm.
Furthermore, the aqueous mixed micelle solutions can also contain additional, water-soluble active agents in - order to produce combination preparations. Examples of such combination preparations include mixtures of water-soluble and fat-soluble vitamins, or preparations :
.
' ' ' ~ ~ ': :
' ~ , ' : .

- 7 _ 2~ 7 containing water-soluble antibiotics, in addition to corticoids.
The micelles of this invention can be used conven-tionally, e.g., for pharmaceutical purposes, e.g., in accordance with German Patent 27 30 570, Acta Anaesthesiol. Scand. 1986, 337-340 and J. Pharm.
Pharmacol. 1988, 85-88.
The aqueous mixed micelle solutions of this inven-tion contain mixed micelles with an average diameter of 2 to 100 nm, preferably 3 to 50 nm. Especially in the case of solutions suitable for injection, the mixed micelles will optimally have an average diameter of 3 to 20 nm.
In addition to the conditions listed above, the water-soluble mixed micelle solutions can also be pre-pared by means of conventional methods by heating the mixtures under vigorous agitation at the temperatures set forth above.
Since the lipoids and also several active agents can be sensitive to oxidation, the process is suitably car-ried out under an inert gas atmosphere, such as nitrogen or argon, and the resultant aqueous mixed micelle solu-tions can be stabilized by the addition of antioxidants, such as sodium ascorbate, tocopherol, or sodium hydrogen sulfite.
The process of this invention can generally be per-formed within a few minutes; it offers the advantage of forming mixed micelle solutions free of organic solvent residues. Additionally, the process of this invention ; can be carried out with conventional mixing and dispers-~ 30 ing techniques (e.g., according to the rotorstator prin-`~ ciple), as customary in pharmaceutical technology (see "The Theory and Practice of Industrial Pharmacy," L.
Lachman, H.A. Lieberman, J.L. Kanig, Philadelphia [1970], p. 481; or "Pharmazeutische Technologie" [Pharmaceutical Technology], K.H. Bauer, K.H. Fromming and C. Fuhrer, Stuttgart/New York tl986], p. 103~, offering good .

:
, ,:

- 8 - 2~3~ 7 process, especially under GMP conditions (good manufacturing practices).
After manufacture has taken place, the thus-obtained aqueous mixed micelle solution can be filtered under sterile conditions and/or can be heat-sterilized at lOO~C
to 140C.
Upon further study of the specification and appended claims, further objects and advantages of this invention will become apparent to those skilled in the art.
lo The practical examples set forth below serve to provide a more detailed explanation of the process according to this invention.
Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The following preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.
In the foregoing and in the following examples, all temperatures are set forth uncorrected in degrees Celsius and unless otherwise indicated, all parts and percentages are by weight.
The entire disclosure of all applications, patents and publications, cited above and below, and of corresponding German application P 39 03 753.3, are hereby incorporated b~ reference.

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- - . ~ ' ' ~' , ' :,' ' .' ' ' . :- , ~: ' ' , ' ' 2a~ 7 Example 1 In a heatable agitating and homogenizing device, 700 ml of 0.02N acetate buffer, p~I 6.0, is heated to 800c while introducing argon. Then, under agitation, 54.2 g of glycocholic acid is added, and the mixture is stirred further until a homogeneous suspension is created (about 5 minutes). Then 90 g of phosphatidyl choline (soybean lecithin) and 10 g of becarnil (= 6-benzoyloxy-4-methoxymethyl-~-carboline-3-carboxylic acid isopropyl ester) are added to the suspension and the latter is agitated at 80C until the dispersion is homogeneous (about 10 minutes). Thereafter, the mixture is combined with 20% aqueous sodium hydroxide solution until a pH of 6.0 is attained, and a clear solution is immediately obtained to which, after cooling, is added water to a final volume of 1000 ml. The thus-obtained aqueous mixed micelle solution is filtered under sterile conditions.

Example 2 In a heatable agitating and homogenizing device, 700 ml of 0.015-molar phosphate buffer, pH 7.0, is heated to 80~C while introducing argon. Then, under agitation, 47.6 g of cholic acid is added and the mixture stirred further until a homogeneous suspension is produced (about 5 minutes). Then 90 g of phosphatidyl choline (soybean lecithin) is added to the suspension and the latter agitated at 80C until the dispersion is homogeneous (about lo minutes). Thereafter, the mixture is combined with 20% aqueous sodium hydroxide solution until a pH of 7.0 is reached, and a clear solution is immediately obtained. Under agitation, 10 g o~ becarnil (= 6-benzoyloxy-4-methoxymethyl-~-carboline-3-carboxylic acid isopropyl ester) is introduced into this solution and is rapidly dissolved. After cooling, water is added ~ ' : :
' ,-2 0 ~ 7 to the resultant solution to a final volume of 1000 ml.
The thus-obtained aqueous mixed micelle solution is sterilized at 121C.

Example 3 s In a heatable agitating and homogenizing device, 700 ml of 0.02N acetate buffer, pH 6.0, is heated to 80C
while introducing argon. Then, under agitation, 54.2 g of glycocholic acid is added and the mixture is stirred further until a homogeneous suspension results (about 5 minutes). Then 90 g of phosphatidyl choline (Phospholipon 100 L, Nattermann Company) and 1.1 g of Cl-PHOCIP (= 5-(4-chlorophenoxy)-4-methoxymethyl-B-carboline-3-carboxylic acid isopropyl ester) are added to the suspension and the latter is stirred at this temperature until the dispersion is homogeneous. After cooling to 40-50rc, the mixture is neutralized with 20%
aqueous sodium hydroxide solution, whereby a clear solution is created having a pH of 6Ø After adding water to the final volume of 1000 ml, the aqueous mixed micelle solution is filtered under sterile conditions and can optionally be sterilized at 121C.

Exa~ple 4 In a heatable agitating and homogenizing device, 700 ml of water for injection purposes is heated to 80C
while introducing argon. Then, under agitation, 54.2 g of glycocholic acid is added and the mixture is stirred further until a homogeneous suspension has been formed (about 5 minutes). Then 90 g of phosphatidyl choline and 2 g of IPMCE (= 5-isopropoxy-4-methyl-~-carboline-3-; 30 carboxylic acid ethyl ester) are added to the suspension and the latter is stirred at this temperature until the dispersion is homogeneous (about 10-15 minutes).
Thereafter the dispersion is combined with 20% aqueous sodium hydroxide solution until a pH of 6.0-6.5 has been ~;

. , .:
. .

-~ ~ ' ' -~2~ 7 attained, thus obtaining a clear solution which, after cooling, is brought to 1000 ml with water. The resultant aqueous mixed micelle solution is filtered under sterile conditions.

Example 5 In a heatable agitating and homogenizing device, 700 ml of water for injection purposes is heated to 80C
while introducing argon. Then, under agitation, 54.2 g of glycocholic acid is added and the mixture is further stirred until a homogeneous suspension is created (about 5 minutes). Then 90 g of phosphatidyl choline and 1 g of Phoco (= 5-(4-chlorophenoxy)-3-(3-ethyl-1,2,4-oxadiazol-5-yl)-4-methoxymethyl-~-carboline) are added to the suspension, and the latter stirred at this temperature until the dispersion is homogeneous (about 10-15 minutes). Thereafter the dispersion is combined with 20%
aqueous sodium hydroxide solution until a pH of 6.0 to 6.5 has been reached, thus obtaining a clear solution which, after cooling, is brought to 1000 ml with water.
The resultant aqueous mixed micelle solution is filtered under sterile conditions.

The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.
From the foregoing description, one skilled in the art can easily ascertain the essential characteristics oP
this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.
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Claims (24)

1. A process for the preparation of an aqueous solution of mixed micelles containing a lipoid and a salt of a bile acid, comprising (a) suspending a free bile acid at a temperature of 40°C to 100°C in an aqueous solution, (b) dispersing the lipoid at a temperature of 40°C
to 100°C in the resultant suspension, and (c) neutralizing the resultant dispersion with a base at a temperature of 0°C to 100°C.

2. A process of claim 1, wherein the resultant aqueous mixed micelle solution further comprises an active agent which is sparingly soluble or insoluble in water.

3. A process of claim 2, wherein the active agent which is sparingly soluble or insoluble in water is dispersed together with the lipoid.

4. A process of claim 2, wherein the active agent which is sparingly soluble or insoluble in water is solubilized in the resultant aqueous mixed micelle solution after neutralization.

5. A process of claim 1, wherein the free bile acid is suspended in an aqueous solution containing an isotonizing additive and/or a water-soluble active agent.

6. A process of claim 2, wherein the free bile acid is suspended in an aqueous solution containing an isotonizing additive and/or a water-soluble active agent.

7. A process of claim 2, wherein the active agent which is sparingly soluble or insoluble in water is a pharmaceutically active agent.

8. A process of claim 6, wherein the active agent which is sparingly soluble or insoluble in water is a pharmaceutically active agent.

9. A process of claim 7, wherein the pharmaceutically active agent is a .beta.-carboline.

10. A process of claim 8, wherein the pharmaceutically active agent is a .beta.-carboline.

11. A process for the preparation of an aqueous mixed micelle solution according to claim 1, wherein the bile acid is a 5.beta.-cholan-24-oic acid derivative of the formula wherein R1 and R2 are two hydrogens, hydrogen and hydroxy, or jointly are oxo, R3 and R4 are two hydrogens, hydrogen and hydroxy, or jointly are oxo, and X is hydroxy, -NH-CH2-CO2H or -NH-(CH2)2-SO3H.

12. A process of claim 1, wherein the lipoid is a phospholipid.

13. A process of claim 2, wherein the lipoid is a phospholipid.

14. A process of claim 2, wherein the resultant micelles have an average diameter of 3 to 50 nm.

15. A process of claim 7, wherein the resultant micelles have an average diameter of 3 to 50 nm.

16. A process of claim 1, wherein the neutralizing step is conducted at a temperature which is the same or lower than the temperature at which the suspending and dispersing steps are conducted.

17. A process for the preparation of an aqueous solution of mixed micelles containing a lipoid and a salt of a bile acid, comprising neutralizing a dispersion of the lipoid and a suspension of a free bile salt with a base at a temperature of 0°C to 100°C, wherein the dispersion and suspension were formed at a temperature of 40°C to 100°C.

18. A solution of aqueous mixed micelles comprising a .beta.-carboline.

19. A solution of aqueous mixed micelles prepared by a process of claim 9.

20. A solution of claim 18, wherein the .beta.-carboline is 6-benzoyloxy-4-methoxymethyl-.beta.-carboline-3-carboxylic acid isopropyl ester, 5-(4-chlorophenoxy)-4-methoxymethyl-.beta.-carboline-3-carboxylic acid isopropyl ester, 5-isopropoxy-4-methyl-p-carboline-3-carboxylic acid ethyl ester, or 5-(4-chlorophenoxy)-3-(3-ethyl-1,2,4-oxadiazol-5-yl)-4-methoxymethyl-.beta.-carboline.

21. A solution of aqueous mixed micelles of claim 19, wherein the .beta.-carboline is 6-benzoyloxy-4-methoxymethyl-.beta.-carboline-3-carboxylic acid isopropyl ester, 5-(4-chlorophenoxy)-4-methoxymethyl-.beta.-carboline-3-carboxylic acid isopropyl ester, 5-isopropoxy-4-methyl-.beta.-carboline-3-carboxylic acid ethyl ester, or 5-(4-chlorophenoxy)-3-(3-ethyl-1,2,4-oxadiazol-5-yl)-4-methoxymethyl-.beta.-carboline.

22. A solution of claim 18, which is in a form suitable for injection.

23. A solution of claim 18, which is in a form suitable for injection.

24. A solution of aqueous mixed micelles containing a lipoid and a salt of a bile acid, substantially free of organic solvent, wherein the mixed micelles have an average diameter of 3 to 20 nm.