Method of Treating Ulcers and Erosions in the Gastrointestinal System Using PGI.sub.2 -Methyl Ester-Beta Cyclodextrin Inclusion Complexes

The invention relates to the use of the inclusion complex of PGI.sub.2 -methyl ester and beta cyclodextrin (PCCD) as well as to pharmaceutical compositions containing same for the prevention and therapy of gastrointestinal ulcers or erosions.

The formation of the inclusion complex of PGI.sub.2 -methyl ester with beta-cyclodextrin is a preferred way for stabilizing the PGI.sub.2 methyl ester. The PGI.sub.2 methyl ester content of the complex amounts to 1 to 15% by weight, preferably 3% by weight. By increasing the stability, the effect of PGI.sub.2 methyl ester may be prolonged in several biological systems.

It is known that some prostacyclines have some strong gastric cytoprotective effects. See B. J. R. Whittle et al, Prostaglandine, Vol. 15, A55 (1978). Unfortunately the cytoprotective effect may be used therapeutically, only with difficulty, because of their chemical and biological instability. The active ingredient decomposes easily so that it has to be produced either freshly or else stored under extreme conditions.

It is also known that among other prostaglandin derivatives, the PGE.sub.2 has proved to be significantly effective both in decreasing the blood loss of the gastric mucosa induced by non-steroidal antiphlogistics as well as in the therapy of peptic ulcers. The use of the PGE.sub.2 is, hiowever, difficult because of its diarrhogen side effects.

It is the object of the invention to provide a new method of treating and/or preventing gastrointestinal ulcers and erosions whether the ulcers or erosions be stress ulcers, peptic ulcers, or ulcers caused by the administration of non-steroidal antiphlogistic agents.

It has surprisingly been found that the stabilizing effect on prostacyclin methyl ester by beta-cyclodextrin is most pronounced when the PGI.sub.2 -methyl ester-beta-cyclodextrin (PCCD) complex is applied in the field of gastrointestinal cytoprotection. Additionally the PCCD has the preferred feature that it does not lose its active ingredient even over a long storage period.

No one as of yet has examined the cytoprotective effect of the prostacycline methyl ester--beta-cyclodextrin complexes. Applicants have found that the cytoprotective effect of the prostacycline methyl ester--beta cylodextrin complex is much more effective than would be expected.

According to the invention a PGI.sub.2 methyl ester-beta-cyclodextrin complex (PCCD) is employed in the treatment or prevention of ulcers or erosions in the gastrointestinal tract. The content of PGI.sub.2 methyl ester in the cyclodextrin inclusion complex ranges from 1 to 15%, and is preferably about 3% by weight. The PCCD may be administered to subjects per se or together with a pharmaceutically acceptable inert carrier.

The preferred method of administration to the patient is oral administration. However, the invention also contemplates administration of the PCCD by injection or by infusion.

The new method of treatment or prevention of ulcers or erosions applies to ulcers or erosions at any point in the gastrointestinal tract from any number of causes. For instance the new method is applicable to the treatment of peptic ulcers. The new method is similarly applicable to the treatment of stress ulcers. Furthermore it is wellknown that non-steroidal antiphlogistic agents such as indomethacin often cause ulcerogenic side effects in patients taking same. Accordingly another feature of the instantly claimed invention is the simultaneous administration of a pharmaceutically effective amount of a non-steroidal antiphlogistic agent together with an effective amount of the PCCD. Alternatively the PCCD may be administered at a different time from when the non-steroidal antiphlogistic agent is administered. Preferably the PCCD is administered subsequently to the administration of the non-steroidal antiphlogistic agent.

Another feature of the invention is a pharmaceutical composition containing a non-steroidal antiphlogistic agent, such as indomethacin, in combination with a pharmaceutically effective amount of the PCCD. The weight ratio of the PCCD to the non-steroidal antiphlogistic agent should range between 1:25 to 1:2500.

The following examples serve to show preparation of the compositions containing the PCCD which are used according to the instantly disclosed invention.

6 mg of prostacyclin methyl ester are dissolved in 2 ml of diethyl ether. Separately 194 mg of anhydrous .beta.-cyclodextrin are dissolved in a mixture of 1 ml of a pH 8 buffer and 5.5 ml of distilled water at 30.degree. C. and the above prostacyclin methyl ester solution is added to the solution obtained. The mixture is stirred for one hour, under a slightly reduced pressure and is then shaken for another two hours at room temperature. The solution is frozen and lyophilized. 198 mg of prostacyclin methyl ester-.beta.-cyclodextrin complex are obtained as an amorphous, water-soluble powder, which decomposes upon heating without melting.

Capsule containing 0.25 mg of active ingredient

The preparation of the capsules

A powder mixture is prepared by dry granulation of a mixture containing the components described in Example 2 in the given proportions. The powder mixture is homogenized and encapsulated in a standard machine to give capsules of 225 mg.

Tablet containing 0.25 mg of active ingredient

The preparation of tablets

Prostacyclin-methyl ester-.beta.-cycloextrin inclusion complex, amylopectine and microcrystalline cellulose together with a corresponding quantity of potato starch are thoroughly admixed in a homogenizing machine in the proportions given in Example 4. The given quantity of stearic acid and talc is homogenized and passed through a No. 100 seave. The fine powder obtained is admixed with the homogeneous powder mixture prepared above, and the mixture obtained is converted into tablets weighing 415 mg each. If desired, the tablets obtained are transformed into dragees or coated tablets.

Injection (lyophilized)

An aqueous solution of the PGI.sub.2 -methyl ester-.beta.-CD complex prepared according to Example 1 is filled into ampoules, so that each ampoule should contain 5 mg of the complex having an active ingredient concentration of 3%. The ampoules are then lyophilized and subsequently sealed under nitrogen. Prior to application the lyophilized powder is dissolved in a physiological sodium chloride solution up to the desired volume.

The following tests have been carried out to show the cytoprotective effects of the inclusion complex of PGI.sub.2 methyl ester and beta-cyclodextrin (PCCD).

For the following tests 200-250 g female wistar rats were fasted for 24 hours before the experiment. Water was given ad libium.

The rats were immobilized on their backs for 24 hours. After immobilization the animals were killed, and their stomachs were prepared for ulcer analysis.

After 24 hours' fasting 30 mg/kg of body weight of indomethacin were administered i.p. Four hours after the administration the animals were killed and their stomachs were prepared for ulcer analysis.

The abovementioned two groups were used as control.

The gastric cytoprotective effect of PCCD was tested by administering it in the following way:

Case A: At 0, 6th, 12th and 18th hour after the immobilization.

Case B: At 0 and 2nd hour after the indomethacin administration.

Administrations were carried out both ip and per os.

In both cases the animals were killed and their stomachs prepared for ulcer analysis.

In each experiment the ulcer index was calculated.

In the calculation of the U.I., each mm.sup.2 of ulcer or erosion is 1 point. Bleeding results in an additional 5 points. Perforation means an additional 10 points. The number of animals is (n=20) in each group.

Mean (%).+-.S.E.M. is calculated. Statistical analysis is done according to the Student's T-Test. Significance level, p is less than 0.05.

A. Robert, Prostaglandins (Suppl.), 21, 89 (1981)

The following method according to the abovementioned reference was employed:

1 ml of ethanol was administered to rats deprived of food for 24 hours orally which caused severe gastric lesions on the corpus mucosa. The cytoprotective substances were applied before giving ethanol p.o. or subcutaneously. As controls, prostacylin (PGI.sub.2) and PGE.sub.2 were used.

Evaluation was carried out by killing the animals and then removing their stomachs. The number of gastric lesions was determined in each case. The dose of the cytoprotective compounds giving a 50% inhibiting effect was determined. The number of gastric erosions in the stomachs of animals not treated with a cytoprotective agent was designated 100%. The results are as follows:

From the data in the table it can be seen that PGI.sub.2 and PCCD while being administered subcutaneously have a stronger cytoprotective effect than PGE.sub.2 while upon oral administration the PGI.sub.2 is more unstable than is PGE.sub.2 (decomposition of the prostacyclin accelerates at the acidic pH of the stomach) so according to this type of application, the PGE.sub.2 proved to be more effective.

The stabilized prostacyclin (PCCD) was more effective by one order of magnitude than PGI.sub.2 per se. The ratio of the ED.sub.50 values for the two substances is respectively 0.24/1.8.

The advantage of PCCD compared with PGE.sub.2 is that when administered parenterally in an amount of 100 to 300 .mu.g/kg, there was no evidence of diarrhogen or other internal problems. Specifically the PCCD did not influence the motility of the gastrointestinal system. When administered in the doses mentioned above, the PCCD did not influence the blood pressure of anesthesized rabbits, nor did it change any of their respiratory parameters.

PCCD has proved to be a very atoxic substance. After having been administered, PCCD containing 30 mg/kg of active ingredient orally to rats of mixed sex, no death appeared after fourteen days. A further advantageous feature of the PCCD is that the amount of active ingredient contained therein does not decrease even after a long storage period, at room temperature. In view of the biological effects stated above, PCCD may be applied in the prevention or therapy of peptic ulcers, acute ulcers and other diseases of the intestines such as ulcerative colitis, Crohn disease, generalized inflammatory bowel diseases, irritable bowel syndromes, and pseudomembranous colitis as well as decreasing the blood losses caused by the ulcerogenic effects of non-steroidal antiphlogistic agents such as indomethacin.

Accordingly the PCCD may be applied together with a non-steroidal antiphlogistic agent. For example it is recommended using an indomethacin tablet containing 25-50 mg of the active ingredient together with PCCD or a PCCD preparation containing 1.0-1000 .mu.g of active ingredient.

The PCCD may be used in the therapy of the diseases mentioned either per se or in the form of the usual pharmaceutical preparations. While preparing these preparations, known excipients, diluents, agents for adjusting the ionic strength and osmotic pressure, as well as agents for promoting the formulation and absorption may be used. The preparations obtained are solid (e.g. tablets, capsules, dragees, powders and pills), liquid (e.g. syrups, drops) or semiliquids (e.g. jellies, suspensions).

In the ulcer therapy, oral administration of the PCCD is advantageous. The necessary doses may vary between 1 microgram and 0.1 mg/kg of body weight of the patient. The precise dose depends on the particular disease and the particular patient to be treated, as well as the seriousness of the disease, the rate at which the medicament arrives at the desired body location, the special sensitivity or reactivity of the organ or patient to be treated. In any event the appropriate specific dose may be determined by those skilled in the art without the need to conduct undue experimentation.