Controlled absorption diltiazen pharmaceutical formulation

Claim 1

A controlled absorption diltiazem formulation for oral administration, comprising a pellet having a core of diltiazem or a pharmaceutically acceptable salt thereof in association with an organic acid and a lubricant, and a multi-layer membrane surrounding said core and containing a major proportion of a pharmaceutically acceptable film forming, water insoluble polymer and a minor proportion of a pharmaceutically acceptable film forming, water soluble polymer, the number of layers in said membrane and the ratio of said water soluble polymer to water insoluble polymer being effective to permit release of said diltiazem from said pellet at a rate allowing controlled absorption thereof over a twelve hour period following oral administration, said rate being measured in vitro as a dissolution rate of said pellet which is substantially pH independent, which when measured in a basket assembly according to U.S. Pharmacopoeia XX substantially corresponds to the following dissolution pattern: (a) from 0 to 10% of the total diltiazem is released after 2 hours of measurement; (b) from 10 to 30% of the total diltiazem is released after 4 hours of measurement; (c) from 20 to 40% of the total diltiazem is released after 6 hours of measurement; (d) from 50 to 80% of the total diltiazem is released after 8 hours of measurement; and (e) from 85 to 100% of the total diltiazem is released after 12 hours of measurement.