Abstract

A controlled absorption diltiazem pellet formulation for oral administration comprises a core of diltiazem or a pharmaceutically acceptable salt thereof in association with an organic acid, and a multi-layer membrane surrounding the core and containing a major proportion of a pharmaceutically acceptable film-forming water insoluble synthetic polymer and optionally a minor proportion of a pharmaceutically acceptable film-forming, water soluble synthetic polymer. The number of layers in the membrane and the ratio of the water soluble to water insoluble polymer, when said water soluble polymer is present, being effective to permit release of diltiazem from the pellet at a rate allowing controlled absorption thereof over not less than a twelve hour period following oral administration. The pellet has a dissolution rate in vitro which when measured in a dissolution apparatus (paddle) according to U.S. Pharmacopoeia XXI in 0.05 M KCl at pH 7.0 results in not more than 35% of the total diltiazem being released after 2 hours of measurement. Not more than 60% of the total diltiazem is released after four hours of measurement and 100% of the diltiazem is released no earlier than after 8 hours of measurement in said apparatus.