Controlled absorption methyldopa pharmaceutical formulation

Claim 1

A controlled absorption methyldopa formulation for oral administration, comprising a pellet having a core of methyldopa or a pharmaceutically acceptable salt thereof in association with an organic acid, 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 said water-insoluble polymer being effective to permit release of said methyldopa from said pellet at a rate allowing controlled absorption thereof over a twenty four hour period following oral administration said rate being measured in vitro as a dissolution rate which is substantially pH independent and which when measured in a Basket Assembly according to U.S. Pharmacopoeia XX at 37° C. and 75 r.p.m., substantially corresponds to the following dissolution pattern: (a) from 25 to 50% of the total methyldopa is released after 1 hour of measurement in said assembly; (b) from 50 to 80% of the total methyldopa is released after 3 hours of measurement in said assembly; (c) from 80 to 100% of the total methyldopa is released after 5 hours of measurement in said assembly; and (d) from 90 to 100% of the total methyldopa is released after 7 hours of measurement in said assembly.