Sustained absorption pharmaceutical composition

Claim 1

A sustained absorption active ingredient-containing pellet for oral administration, said pellet comprising a core of about four parts of an active ingredient selected from the group consisting of anhydrous theophylline, aminophylline, dyphylline, theophylline calcium salicylate and theophylline sodium glycinate and about one part of an organic acid selected from the group consisting of citric acid, tartaric acid, succinic acid, malic acid, ascorbic acid and fumaric acid or a mixture thereof embedded in a polymeric material which contains a major proportion of a water-soluble polymer and a membrane of a film-forming polymer or mixture thereof surrounding the core whereby said active ingredient is released at a controlled rate in an aqueous medium and said pellet has a dissolution rate in an aqueous medium which is substantially independent of pH and which when measured in a basket assembly according to U.S. Pharmacopoeia XX at 37° C. and 75 r.p.m., in a buffer solution at pH 7.5 has the following characteristics: (a) from 0 to 15% of said active ingredient is released after two hours of measurement in said assembly; (b) from 15 to 35% of said active ingredient is released after 7 hours of measurement in said assembly; (c) from 45 to 65% of said active ingredient is released after 13 hours of measurement in said assembly; and (d) from 80 to 100% of said active ingredient is released after 24 hours of measurement in said assembly.