| abstract |
A pH-dependent sustained release pharmaceutical pellet composition and a method of administering the same to a patient at a predetermined dosage and interval, said pellet composition comprising: a core element containing a therapeutically effective amount of theophylline, xanthine or a derivative thereof as the active ingredient and a coating on said core element which comprises the following components: (a) at least 40% of a matrix polymer which is insoluble at a pH of from 1 to 7.5 and contributes to the control of the rate of release of the active ingredient in the stomach and intestines; (b) from 1 to 30% of an enteric polymer which is substantially insoluble at a pH of from 1 to 4, sufficient to delay the release of the active ingredient in the stomach, but which is soluble at a pH of from 6 to 7.5 so as not to substantially delay release in the intestines; (c) from 1 to 60% of a compound soluble at a pH of from 1 to 4, sufficient to enable initiation of release of the active ingredient in the stomach; said percentages being by weight based on total weight of components (a), (b), and (c); the ratio of the components (a), (b), and (c) in said coating being effective to allow the initiation of the release of the active ingredient in the stomach at a slow rate and to control the release in the intestines at a rate faster than that in the stomach such that a dose of the pellet composition delivers to the patient a therapeutically effective amount of said active ingredient over the course of said predetermined interval, said coated core element having a diameter of from 510 to 2400 microns. |