HU203479B - Process for microcapsulating trh or analogues - Google Patents

Abstract

The present invention relates to a sustained release microcapsule comprising a polymer and a delayed release microcapsule containing TRH, an analog thereof or a salt of at least pKa-4.0 with a weak acid, as a polymer. a fatty acid homopolymer or copolymer thereof, in the form of an oily phase containing from 5 to 80% by weight of organic solution and from 2 to 15% by weight of the active ingredient and water based on the polymer, where the weight ratio of the oily phase to the aqueous phase is 1 -200: 1, water-in-oil emulsion, emulsion dispersant, preferably polyvinyl alcohol or gelatin, in an aqueous solution of 0.01 to 20% by weight in water-in-oil-in-water emulsion and the solvent of the oily phase is distilled off. EN 203 479 B Scope of the description: 12 pages (including Figure 1) -1-

Description

The present invention relates to a novel process for the preparation of microcapsules containing TRH.

Various types of microcapsules are known. For example, European Patent Publication No. 52,510 discloses a microcapsule produced by a phase separation process using mineral oil and vegetable oil as coacervating agents.

The capsule thus prepared is capable of joining one part with the other on the basis of adhesion to the particle-a-particle and / or easily adapting to the fracture surface, including during manufacture. As a result, the capsule is easily ruptured and dispersed. A further disadvantage is that more organic solvents are used in the preparation and the remaining solvent in the microcapsule causes further problems.

European Patent Publication No. 145,240 discloses a process for making a microcapsule by drying it in water. By this method, the active ingredient can be microencapsulated successfully, and due to its favorable release properties, the intended therapeutic effect can be assured.

A microencapsulation process based on a three-phase emulsion is described in U.S. Patent No. 3,523,906. U.S. Pat. The disadvantage of the process is that the initial release of the active ingredient is relatively high, and the size and shape of the microcapsules are irregular.

If the active ingredient is to be administered in the form of a microcapsule by living organizers, the microcapsule must meet a number of requirements, since the therapeutic effect is highly dependent on the relationship with the internal functions of the living organism. It is therefore necessary that the microcapsule satisfies the resulting requirements.

However, the known microcapsules are barely technologically capable of meeting these requirements.

For example, for some drugs, the membrane structure of the microcapsule will be relatively coarse or crude, and thus release the drug more rapidly than desired during the initial phase, and thus the rate of drug release will be significantly different from the time constant.

For some drugs, the amount of drug incorporated into the microcapsule will become lower within the generally used concentration limits, which causes particular problems.

Known drug agents include TRH and analogues (Neuropharmacology, 20, 947-957 (1981); Neuropharmacology, 23, 339-348 (1984); Brain Research Reviews, 4, 389-403 (1982); European Patent Publication No. 123,444], however, its microencapsulation has not been solved.

It has been found that the advantageous properties of the microcapsule in water soluble TRH-containing sustained release formulations are closely related to the physicochemical properties of the active ingredient and the active compound concentrate.

The present invention therefore relates to a process for the preparation of a microcapsule, wherein the homopolymer or copolymer of a polyhydroxy fatty acid having a molecular weight of 1000-100,000 is in the form of an aqueous solution containing 5-80% by weight of organic solution and 2-15% by weight of TRH, analogue thereof. or an aqueous phase comprising a weak acid salt of at least pKa-4.0 and water, wherein the weight ratio of the oil phase to the aqueous phase is from 1 to 200: 1, to form a water-in-oil emulsion, of which dispersant, preferably polyvinyl alcohol or a 0.01% to 20% by weight aqueous solution of gelatin in water-in-oil-in-water emulsion is prepared and the solvent of the oily phase is distilled off.

In the process of the invention, the compound of formula (I) is preferably used as the TRH (thyrotropin releasing hormone) or TRH analogue.

X is a 4-, 5- or 6-membered saturated or unsaturated heterocyclic group containing one, five or six membered heteroatoms selected from the group consisting of nitrogen, oxygen and / or sulfur,

Y is imidazol-4-yl or 4-hydroxyphenyl,

Z is methylene or sulfur,

R ¹ and R ² are the same or different and are hydrogen or C1-4 alkyl,

R ³ is hydrogen or 3,4-dihydroxyphenylethylaminocarbonyl, provided that when Z is sulfur, X is (e), Y is imidazol-4-yl, R ¹ , R ² and R ³ are hydrogen.

The heterocyclic group in X may be, for example, a), (b), (c), (d), (e), (f) or (g).

C 1-4 alkyl in R ¹ and / or R ² is preferably C 1-3 alkyl such as methyl, ethyl, propyl or isopropyl.

The compounds of formula I are preferably prepared from 2 to 4 amino acids, an amino acid derivative and / or an amino acid analogue.

For example, the compound of formula (I) may be pyroGlu-His-ProNHj (TRH), α-butyrolactone carbonyl-HisProNHj (DN-1417), orothyl-His-ProNH ₂ (CG-3509), 2-methyl-3- oxo-tetrahydro-thiazin-5-ylcarbonyl-His-ProNH ₂ (CG-3703), pyroGlu-Tyr-ProNH ₂ (Ro 10 2928), pyroGluHis-ProNH- (3,4-dihydroxyphenylethyl) ( Ro 10 9430), pyroGlu-His-ProNH- (3,4-dihydroxyphenylethylaminocarbonyl) (Ro 10 8802), pyro-2-aminoadipyl-His-thiazoline-4-carboxamide (MK-771 ), pyroGlu-His- (3-methyl) -ProNH ₂ (RX 74 355), pyroGlu-His- (3,3-dimethyl) -ProNH ₂ (RX 77 368), azetidinon-4-ylcarbonyl-His- ProNH ₂ (YM-14,673) and Related Compounds The following compounds are described in the following literature:

Neuropharmacology, 20,947-957,1981 (TRH, CG3509, CG-3703, Ro 102,928);

Neuropharmacology, 23, 339-348, 1984 (CG-3509, DN-1417, MK-771, RX 77,368);

Brain Research Reviews, 4, 389-403, 1982 (CG3509, CG-3703, MK-771, DN-1417, RX 77 368, RX 74 355);

HU 203 479 Β

European Patent Publication No. 123,444 (YM-14,673).

Among these compounds of formula I, TRH, DN-1417 CG-3509 is preferred.

The weak acid which forms the salt with the above compounds (peptides) and has a pKa-4.0 value can be inorganic or organic acid. Preferred inorganic acids are carbonic acid and boric acid. Preferred organic acids are monocarboxylic acids, especially C 1 -C 3 alkane monocarboxylic acids such as acetic acid or propionic acid.

Weak acids of at least pKa-4.5 and at most pKa-13, in particular up to pKa-9.5, are preferred.

The oil phase polymer is a water-insoluble or water-insoluble and biocompatible polymer. Preferably, the acidic polymer is used. In particular, they are biodegradable polymers. Examples of such fatty acid esters include polylactic acid, polyglycolic acid, polylactic acid glycolic acid, poly-e-caprolactone, polycitric acid, poly malic acid.

The polymers may be used in the form of homopolymers or copolymers of two or more different acids.

Preferably the polymer used for the preparation of an injectable composition is a biodegradable polymer, such as a copolymer or mixture of polylactic acid, lactic acid and glycolic acid. For the lactic acid / glycolic acid ratio, copolymers having about 40-95 mol% lactic acid and about 605 mol% glycolic acid, especially about 50-95 mol% lactic acid and about 50-5 mol% glycolic acid, preferably about 60- They contain 90 mol% lactic acid and about 40-10 mol% glycolic acid.

The polymers preferably used in the process of the invention have an average molecular weight of about 1000 to 100,000, more particularly of about 2,000 to 50,000, preferably about 5,000 to 30,000.

Preferably, the oily phase is a solution of one of the above-mentioned polymers in an organic solvent.

Organic solvents include solvents that are poorly miscible with water and have low boiling points and are highly soluble in the polymer, such as halogenated alkanes (e.g., dichloromethane, chloroform, chloroethane, trichloroethane or carbon tetrachloride), ethyl acetate, ethyl ether, cyclohexane, benzene, n-hexane and toluene.

The solvent may be used alone or in a mixture of two or more solvents.

Relatively polar and low-boiling dichloromethane and chloroform are particularly preferred.

In the first step of the microencapsulation process according to the invention, the aqueous phase is prepared by dissolving 2-15% by weight, preferably 5-12% by weight, particularly preferably 7-12% by weight, of TRH, TRH analogue or their weak acid salts in water.

If desired, an inert polymer retention agent, pH adjusting agent, stabilizer and / or preservative are added to the solution.

Water-soluble but poorly soluble in the organic solvent of the oily phase, which forms a highly viscous semi-solid matrix directly in the aqueous solution, or a semi-solid or solid matrix under external conditions such as temperature, pH, metal ion (e.g. **, Al ***, Zn **) and / or chemical condensing agents (eg glutaraldehyde, acetaldehyde).

Thus, natural or synthetic rubbers and polymers can be used as retention agents. Suitable pH adjusting agents include carboxylic acid, acetic acid, oxalic acid or tartaric acid, and their sodium or potassium salts, hydrochloric acid or sodium hydroxide.

Suitable stabilizing agents are, for example, albumin, gelatin, citric acid, sodium salt of ethylenediaminetetraacetic acid, dextrin, glucose, sorbitol or other sugars, glycerol or other polyols, and sodium bisulfide, and the like. Suitable preservatives are, for example, parahydroxybenzoic acid esters (e.g., methyl paraben, propyl paraben), benzyl alcohol, chlorobutanol and thimerosal.

The peptide content of the aqueous phase is generally 5 to 80% by weight, preferably 15 to 70% by weight. Within the stated concentration range, good results are obtained even without the use of said active substance retention agent.

The resulting aqueous solution is added to the solution containing the polymer (oil phase) and emulsified to form a water-in-oil emulsion.

Any dispersion process may be used in the emulsification process, including, for example, intensive shaking, agitation such as with a propeller mixer or turbine mixer, use of a colloid mill, homogenization, or ultrasound.

The resulting water-in-oil emulsion is converted into a three-phase water-in-oil-in-water emulsion which is dried in water. In this process, the water-in-oil emulsion is added to the aqueous phase serving as the third phase, and the solvent for the oil phase is removed after the water-in-oil-in-water emulsion is prepared. This gives the desired microcapsule. In the preparation of a water-in-oil-in-water emulsion, the viscosity of the first aqueous phase and the viscosity of the water-in-oil emulsion significantly influence the shape of the desired microcapsule as well as the amount of active ingredient taken up. fall into the appropriate ranges. In particular, the viscosity of the water-in-oil emulsion has a significant influence on the amount of active ingredient taken up, so an emulsion with a viscosity of 15010 000 cp is preferably used.

In this process, as well as during the drying of the water-in-oil-in-water emulsion in water, the relationship between the active ingredient and the polymer significantly influences the microcapsule shape, the amount of active ingredient and the initial release. preparation of an active release microcapsule.

Accordingly, the aqueous peptide solution prepared under the above conditions is converted to a water-in-oil emulsion in a volume ratio such that the drug / polymer ratio is within the stated limits. The emulsion

The temperature is adjusted to the specified limits and then poured into the second aqueous phase at this temperature. Subsequent removal of the organic solvent yields the microcapsule. In this case, the water-in-oil volume ratio, the water-in-oil emulsion temperature and the temperature of the second aqueous phase influence the drug-polymer relationship and thus the optimum conditions will be determined by the type and amount of drug and polymer employed.

The concentration of polymer in the oily phase depends on the type of polymer used, but is generally about 5 to about 80% by weight, preferably about 30 to about 60% by weight.

The volume ratio of water-in-oil emulsion depends on the type and amount of active ingredient, polymer and solvent used. The oily phase is generally employed in an amount of from 1 to 200 parts by weight, preferably from 1 to 100 parts by weight, based on 1 part by weight of the aqueous phase.

The temperature of the water-in-oil emulsion and the second aqueous phase may vary from -10 ° C to the boiling point of the organic solvent used, preferably at a temperature of 0-35 ° C.

An emulsifier is added to the second aqueous phase. Suitable emulsifiers are stable oil-in-water emulsifiers, such as anionic surfactants (e.g., sodium oleate, sodium stearate, sodium lauryl sulfate, etc.), nonionic surfactants (e.g., polyoxyethylene) sorbitan. fatty acid ester (Tween 80 or Tween 60), polyoxyethylene cassette oil derivatives (HCO-60 or HCO-50, Nikko Chemicals), etc.] and polyvinylpyrrolidone, polyvinyl alcohol, lecithin and gelatin . They may be used singly or in a mixture of two or more materials. Polyvinyl alcohol, carboxymethyl cellulose and gelatin, and mixtures thereof, are preferred. The amount of emulsifier is generally 0.01 to 20% by weight, preferably 0.05 to 10% by weight.

Any known method of solvent removal of the oily phase may be used for drying in water. Alternatively, the water-in-oil-in-water emulsion may be simply mixed, for example with a propeller mixer or magnetic stirrer, or optionally heated and / or introduced with nitrogen gas. The solvent may also be removed by gradual reduction of pressure or by rotary evaporation. The time required for solvent removal may be reduced by gradually increasing the temperature of the water-in-oil-in-water emulsion after the polymer has solidified properly.

The resulting microcapsules are collected by centrifugation or filtration, washed repeatedly with distilled water to rinse the remaining water-soluble active ingredient and other substances adhering to the surface of the microcapsule, and if necessary, the remaining moisture in the microcapsule and freeze dried in the microcapsule membrane.

If desired, the microcapsules may be fractionated, for example, by sieving, separating the desired particle size fraction from the fraction of the oversized microcapsules. For use as a suspension, the microcapsule can be used with any particle size at which dispersibility and penetration are desired. The average diameter in this case is from about 0.5 to about 400 microns, preferably from about 2 to about 100 microns, the exact value of which is determined by the desired release rate.

The process of the present invention allows the amount of active ingredient, i.e. peptide, to be incorporated into the microcapsule, and the wall membrane of the resulting microcapsule is compact and reduces excessive initial drug release.

The microcapsules obtained by the process of the invention have a number of advantages. For example, spherical, regular-shaped microcapsules are obtained which do not aggregate during production, the solvent removal from the oily phase is easily controlled and allows the surface structure (i.e., the number and size of micropores) of decisive importance to be released.

The microcapsules obtained by the methods of the invention can be used as such by implantation into a living organism, but they can also be used to produce various dosage forms.

Dosage forms made from microcapsules may include injectables, oral formulations, nasal formulations, and rectal, urethral, and vaginal suppositories, and the like.

For use as an injection preparation, the microcapsules can be formulated as an aqueous suspension for delayed release, with the addition of a dispersant (e.g., Tween 80, HCO-60, carboxymethylcellulose or sodium alginate), a preservative (e.g., methyl paraben or propyl). paraben), an isotonizing agent (e.g., sodium chloride, mannitol, sorbitol or glucose). The injection preparation may also be an oily suspension prepared with a vegetable oil such as sesame oil or corn oil.

One or more excipients (e. G., Mannitol, sorbitol, lactose or glucose) are added to the suspension of the microcapsule for preparation of an injection with improved stability, then re-dispersed and freeze-dried or spray-dried to form a solid formulation. The suspension is used in distilled water for injection, or other suitable dispersing medium.

The dosage of the sustained release formulation produced will be based on the type and amount of peptide active agent employed, the type of formulation, the duration of drug release, the treated animal (e.g., warm-blooded mammal such as mouse, rat, horse or bovine, or human). depends on the effective dose of the active ingredient used. For example, a single dose for mammals is preferably in the range of 0.1 to 100 mg, particularly preferably 0.2 to 50 mg / kg body weight, in microcapsules. Suspended-41 injected

The volume of the reaction is generally about 0.1 to 5 mL, preferably about 0.2 to 3 mL.

As described above, a pharmaceutical composition is provided which, in the form of microcapsules, contains a water-soluble active ingredient and a biocompatible polymer as described above in an amount greater than the usual single dose, and which provides sustained release of the active ingredient over a prolonged period.

Advantageous effects of the present invention include the production of a solid microcapsule wall, an increase in the amount of drug absorbed, and a reduction in the initial release by reducing the diffusion of areas close to the surface layer of the microcapsule due to the interaction between acidic polymer groups and basic groups of said peptide. As a result, among the various peptides containing basic groups, peptides with stronger basicity groups and / or more basic groups are more effective in reducing excess initial release and increasing the amount of drug taken up. such as lysine, alginine, or histidine, or chemically coupled to a physiologically active non-peptide-like organic compound with a peptide chain containing the above basic groups.

The sustained release formulations of the present invention have the following characteristics:

(1) A favorable delayed release of the peptide can be assured in the various dosage forms. Specifically, if a longer injection treatment is required to produce the desired therapeutic effect, the effect can be achieved by administering only one injection weekly, monthly or yearly, since release of the active ingredient can be achieved over a much longer period of time compared to known sustained release formulations. used in the form of injection containing a biodegradable polymer, surgical implantation is not required as it can be readily applied by subcutaneous or intramuscular injection of known injection suspensions. No removal or extraction required.

(3) Compared to known methods for preparing and drying water-in-oil-in-water three-phase emulsions, the process of the present invention incorporates the active ingredient more efficiently into the microcapsule without the addition of a separate active substance retention agent to the first aqueous phase. administered. In addition, fine, round and regular shaped microcapsules can be obtained.

(4) Compared to known processes for preparing water-in-oil-in-water emulsions and drying in water, the resulting microcapsule significantly reduces the excessive initial release and thus provides a more sustained and sustained release formulation.

The following examples illustrate the invention.

Example 1

Dissolve 50-1000 mg TRH (free form) in 0.625 ml water. The solution was added to a solution of 5 g lactic acid / glycolic acid copolymer [lactic acid / glycolic acid 75:25, average molecular weight 14,000, hereinafter PLGA (75/25) -14,000, or PLGA briefly] in 6.25 ml dichloromethane. The mixture was stirred in a small homogenizer (Polytron, Kinematics, Switzerland) for 3-60 seconds. The resulting emulsion was cooled to 18 'C and poured into 1.250 ml of 0.25% aqueous polyvinyl alcohol (PVA) at 18' C. The entire mixture is converted to a water-in-oil-in-water emulsion using a turbine homogenizer mixer. The emulsion is then stirred to evaporate dichloromethane to solidify the first water-in-oil emulsion. The solid phase is separated by centrifugation. This is re-dispersed in distilled water and the unbound active substance and other substances are washed with water.

The collected microcapsules are freeze-dried until the solvent and water are completely removed to give the desired powder product.

The resulting microcapsule contains about 1-20% by weight of TRH based on PLGA. The exact amount of active ingredient in the freshly prepared product and in the microcapsules stored at 37 ° C in the pH 7.0 phosphate buffer for one day is examined separately. The measurement results are shown in Table 1.

Table 1

Item TRH concentration (the) recorded quantity (%) Residual volume after one day (%) (b) 25 1 82.1 34.3 51 2.5 88.6 85.4 26 5 105.2 83.7 52 7.5 95.9 91.2 27 10 105.9 74.0 101 12 83.7 84.6 102 15 72.1 83.0 28 20 472 61 (2

(a)% by weight relative to PLGA (b) -1/30 M phosphate buffer, pH 7.0, 37 C (in n-2 case).

If the concentration of TRH is 1% by weight relative to PLGA, the amount of drug incorporated in the microcapsule is relatively low and release reaches 65.7% on the first day. In contrast, at concentrations of 2.5 to 15% by weight, good microcapsules are obtained. the amount of active substance absorbed is very high and the first day release (initial release) is relatively low. When the concentration of TRH reaches 20% by weight with respect to PLGA, the amount of drug taken up again decreases and the initial release increases. The reason for this is probably the breakage of the water-in-oil emulsion during water drying and the formation of water in the polymer capsule wall5

EN 203 479 Β increase in the number of gymnasts caused by the increase in hydrophilic drug content.

For comparison, a microcapsule was prepared as described above, except that 53 mg of TRH was dissolved in 03 ml of water, and that a relatively large amount, more specifically 4 g or 6 g of PLGA was dissolved in 43 ml of dichloromethane and the viscosity of the oil in oil emulsion is increased to about 2000 cp during transport in water. The amount of TRH relative to PLGA was 1.33% and 0.88% by weight, respectively. The resulting microcapsules have a 77% and 98% uptake, respectively. However, the initial drug release is 71% and 67%, respectively, as no delay can be achieved at all.

Example 2

TRH (free form) (100 mg) is dissolved in 0.5 ml of distilled water or an equimolar amount of 03 ml aqueous solution of maleic acid, citric acid, acetic acid or hydrochloric acid, and a solution of 5 g PLGA in 5 ml dichloromethane is added. A microcapsule containing TRH or a salt thereof is then prepared as described in Example 1. In the preparation of the three-phase emulsion, both liquid phases are set at 15 ° C.

Table 2 shows the drug uptake and initial release of the resulting microcapsules.

Table 2

item Number TRH salt bulk chemicals recording (%) agent After 1 day (%) (a) 53rd free 983 84.2 54th tartrate 93.2 0 55th citrate 91.8 0 56th acetate 90.4 66.8 57th hydrochloride 85.7 1.2

in the case of (a) -n-3

The incorporation of TRH is good in all cases due to the high viscosity of the water-in-oil emulsion. On the other hand, however, the amount of TRH in this example is relatively low, more than 2% by weight relative to PLGA, and it is therefore believed that the properties of the microcapsule are strongly influenced by the type of salt used. The effect of the acid can be clearly demonstrated. While free-form TRH shows only 15.8% release on the first day, the active substance is almost completely released in the initial phase, more preferably 98.8-100% when tartaric, citric and hydrochloric acid is used. In contrast, when acetic acid, a weak acid, is added, the initial release is relatively low (33.2%) when 5% w / w of TRH is even better (22.6%), but slightly more than free TRH.

The above results suggest that the uptake of active ingredient is influenced by the active substance / polymer interaction by forming a stable water-in-oil or water-in-oil-in-water emulsion. It also influences the reinforcement of the microcapsule wall and the reduction of initial release by inhibiting the diffusion and release of the drug through the microcapsule. The low pKa acid exerts a beneficial effect because it is involved in said interaction by means of lactic or glycolic acid residues.

Example 3

The microcapsule prepared in Example 1 measured in vitro drug release and in vivo drug release (amount of drug remaining in the microcapsule at the site of administration) administered subcutaneously to the rat. The measurement results are shown in Tables 3 and 4.

Table 3

In vitro drug release (% of drug remaining in the microcapsule, in n-3 cases)

Active ingredient Theorem One day lhét 2 weeks 3 weeks 4 weeks TRH 50 94.5 82.2 59.0 44.6 7.8

Table 4

In vivo release (% of active ingredient remaining in the microcapsule, in n-3 cases)

agent Item One day lhét 2 weeks 3 weeks 4 weeks TRH 50 79.8 72.8 31.3 16.7 3.2

The measurement results clearly show that microcapsules made from PLGA (lactic acid / glycolic acid ratio 75:25, average molecular weight 14,000) and 5% by weight of free TRH based on the polymer also show favorable release in vivo, i.e. low initial release is followed for a long time by well-controlled release of the active ingredient. Electro-microscopy shows that the microcapsule produced is spherical and regular in shape with an average diameter of 10-40 microns. Microcapsules can be easily and smoothly injected using a dispersion medium having a needle size 23-22.

Example 4

A first aqueous phase was prepared by dissolving 5CL1000 mg CG-3509 (free form) in 0.5 mL water. To obtain the oily phase, 5 g of PLGA is dissolved in 6.25 ml of dichloromethane. The oil phase was added to the first aqueous phase while stirring with a Polytron (Kinematics, Switzerland). The resulting water-in-oil emulsion was cooled to 15-18 'C and poured into 1.250 ml of 0.5% w / w aqueous gelatin solution, cooled to 18' C, followed by turbine homogenization.

HU 203 479 Β produces a water-in-oil-in-water emulsion. The emulsion is then stirred to evaporate the dichloromethane from the oily phase to solidify the oily phase. The resulting microcapsules were collected by centrifugation, washed with distilled water, and freeze-dried until complete removal of solvent and water residues. Thus, a microcapsule containing CG-3509 is obtained in powder form.

The drug content of the resulting microcapsule and the amount of drug remaining in the microcapsule stored at 37 ° C in phosphate buffer for one day at pH 7.0 are determined. The results are shown in Table 5.

Table 5

Item CG-3509 concentration (the) recorded quantity (%) the rest quantity After 1 day (%) 106 1 91.7 44.1 107 25 95.6 81.6 108 5 113.5 88.4 110 10 88.8 88.0 111 20 45.8 78.7

(a) Amount of -CG-35O9 expressed as a percentage by weight of PLGA.

Similarly to TRH used in Example 1, a large amount of drug was taken up and advantageously delayed release microcapsules, whereby the first daily release (initial release) is significantly reduced when CG3509 is 2.5- based on PLGA. 10% by weight.

Example 5

Dissolve 600 mg TRH (free form) in 0.36 ml distilled water to give a first aqueous phase and then dissolve 5.4 g PLGA in 6.7 ml dichloromethane to give an oil phase. A microcapsule containing TRH is then prepared as described in Example 1. To prepare the three-phase emulsion, both liquid phases are cooled to 19 ° C.

Example 6

700 mg TRH (free form) was dissolved in 0.29 ml distilled water and 8.29 ml PLGA dissolved in dichloromethane (75:25 lactic acid / glycolic acid, average molecular weight 10,000) was added. A microcapsule containing TRH is then prepared as described in Example 1. During the formation of the three-phase emulsion, the liquid phase is cooled to 18 ° C.

The resulting microcapsule has a low initial release since the amount of TRH remaining in the in vitro release (pH 7.0 in phosphate buffer for 1 day, 37 'C) is 92.4%.

Example 7

A microcapsule was prepared as described in Example 4 except that PLGA (75/25) -5000 and Mk-771 were used instead of PLGA (75/25) -14000 and CG-3509.

Example 8

A microcapsule was prepared as described in Example 4 except that PLGA (75/25) -10,000 and DN1417 were used instead of PLGA (75/25) -14,000 and CG-3509.

Example 9

A microcapsule was prepared as described in Example 4, except that PLGA (50/25) -20,000 and YM-14,673 were used instead of PLGA (75/25) -14,000 and CG-3509.

Example 10

A microcapsule was prepared as described in Example 4, except that PLGA (75/25) -20,000 and RX-77,368 were used instead of PLGA (75/25) -14,000 and CG-3509.

Example 11

A microcapsule was prepared as described in Example 4, except that polylactic acid (PLA-20,000) and TRH were used instead of PLGA (75/25) -14,000 and CG-3509.

Example 72

A microcapsule was prepared as described in Example 4, except that PLA-10,000 and CG-3703 were used instead of PLGA (75/25) -14,000 and CG-3509.

Example 13

A microcapsule was prepared as described in Example 4, except that instead of PLGA (75/25) -14000 and CG-3509 a copolymer of hydroxybutanoic acid and glycolic acid (50/50-20,000) and TRH were used.

Claims (9)

A process for the preparation of a delayed release microcapsule containing a polymer and the active ingredient TRH, an analogue thereof or a weak acid salt having a pKa-4.0 value of at least pKa-4.0, characterized in that the polymer is a homopolymer of polyhydroxy fatty acids An aqueous phase containing from 80% by weight of an organic solution in a concentration of -80% by weight and an aqueous phase containing from 2% to 15% by weight of the active ingredient and water based on the polymer, wherein the oil phase forms a water-in-oil emulsion; mixing the emulsion with an aqueous solution of a dispersant, preferably polyvinyl alcohol or gelatin, at a concentration of 0.01 to 20% by weight, to form a water-in-oil-in-water emulsion and distilling off the solvent of the oily phase. HU 203 479 Β 2. A process according to claim 1 wherein the active ingredient is a compound of formula I wherein X is (a), (b), (c), (d), (e), (f) or (g), Y is imidazol-4-yl or 4-hydroxyphenyl, Z is methylene or sulfur, ^R1 and ^R2 signals of the same or different and represent hydrogen or C1-4 alkyl, R ³ is hydrogen or 3,4-dihydroxyphenylethylaminocarbonyl, with the proviso that when Z is sulfur, X is (e), Y is imidazol-4-yl, R ¹ , R ² and R ³ are hydrogen. 3. A process according to claim 2 wherein the compound of formula I is used R ¹ and R ² is hydrogen, X, Y, Z and R ³ are as defined in claim 2. 4. A process according to claim 1 wherein the active ingredient is pyroGlu-His-ProNH ₂ or orothylHis-ProNH ₂ . The method of claim 1, wherein the TRH or analog thereof is used in free form. 6. The process of claim 1 wherein the TRH or analog thereof is used in the form of a salt with an inorganic acid or an organic acid having a pKa-4.0 of at least. The process according to claim 6, wherein the organic acid is lower alkane monocarboxylic acid having a pKa-4.0 value of at least. 8. The process of claim 1 wherein the polymer is copolymer of lactic acid and glycolic acid. 9. The process of claim 1, wherein the active ingredient is an aqueous phase comprised of 5 to 15% by weight of TRH, an analogue or a salt thereof, and water.