Substained release microcapsule of physiologically active compou

Details Substained release microcapsule of physiologically active compou Substained release microcapsule of physiologically active compou

1995-12-22

2000-09-05

Bawa, Raj

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Capsules

424489, 424426, 424490, 514963, A61K 952

Patent

active

061139416

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a microcapsule using a biodegradable polymer to encapsulate a physiologically active substance.


BACKGROUND OF THE INVENTION

In general, drugs that are slightly water-soluble at pH 6 to 8 are slightly absorbed into the digestive tract after oral administration because of their low dissolution rates. In order to improve the solubility of the drugs, the slightly water-soluble drugs have been formulated as readily water-soluble salts, or a solution adjuvant is introduced as an additive. However, in the case of hydrochloric acid salts for example, hydrochloric acid sometimes separates from the hydrochloric acid salt during storage. When a solution adjuvant is added, the resulting tablets contain so many ingredients and sometimes become so large that it becomes difficult to take them. In addition, because the acid that is added as an additive readily dissolves and disappears, the effects of improving the solubility also disappear.
Pharmaceutical Research, Vol. 8, No. 1, p. 101 (1991) reports studies on nanocapsules which contain the slightly water-soluble drug indomethacin. However, indomethacin is not readily soluble in water at a pH no higher than 3. In addition, no improvement in the absorption of the drug has been achieved in the study.


DISCLOSURE OF THE INVENTION

The present inventors have designed and studied a microcapsule containing a physiologically active substance that is soluble in water at a pH no higher than about 3 by using a biodegradable polymer as a base. As a result, it has been found that a microcapsule prepared by adding to a biodegradable polymer a physiologically active substance that is water-soluble at a pH no higher than about 3 and dissolving the mixture in an organic solvent gradually releases a water-soluble low molecular weight free acid and the physiologically active substance at the same time after degradation of the base occurs in the digestive tract after oral administration. It has also been found that the microcapsule solubilizes a physiologically active substance that is normally insoluble in the digestive tract from the duodenum to the rectum, thereby improving the absorption of the physiologically active substance. After further studies based on these findings, the present invention has been completed.
The present invention provides a microcapsule comprising a physiologically active substance which is water-soluble at a pH no higher than about 3, and a biodegradable polymer.
The present invention also provides a microcapsule which is obtainable by dissolving in an organic solvent a physiologically active substance which is water-soluble at a pH no higher than about 3 together with a biodegradable polymer, and then subjecting the resulting solution to in-water drying or spray drying.
The present invention also relates to a process for producing a microcapsule which comprises dissolving in an organic solvent a physiologically active substance which is water-soluble at a pH no higher than about 3 together with a biodegradable polymer, and then subjecting the resulting solution to in-water drying or spray drying.
The present invention further relates to a method of treating ulcer or hypertension in a mammal which comprises administering to such mammal in need thereof an effective therapeutic amount of the above microcapsule.
The present invention still further relates a method of enhancing absorption of a slightly absorbable physiologically active substance, which comprises encapsulating the slightly absorbable physiologically active substance by dissolving in an organic solvent the slightly absorbable physiologically active substance together with a biodegradable polymer, and then subjecting the resulting solution to in-water drying or spray drying.
The present invention also provides use of a slightly absorbable physiologically active substance and a biodegradable polymer for manufacture of a microcapsule.
The present invention also provides use of the above microcapsule for enhancing absorption of a slightly absorbable

REFERENCES:
Pharaceutical Research, N. Ammoury et al., vol. 8, No. 1, Jan. 1991, "Jejunal Absorption, Pharmacological Activity, and Pharmacokinetic Evaluation of Indomethacin-Loaded Poly (d,1-Lactide) and Poly (Isobutyl-Cyanoacrylate) Nanocapsules in Rats".
Science, J. Folkman et al., pp. 719-725, Aug. 1983, "Angiogenesis Inhibition and Tumor Regression Caused by Heparin or a Heparin Fragment in the Presence of Cortisone".

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