The influence of drug and diluent particle size on the in vitro release of drug from hard gelatin capsules

Abstract

Abstract The in vitro release of a drug from capsules containing different proportions of controlled particle size fractions of acetylsalicylic acid and lactose, has been assessed in terms of the time for 50% of the drug content of the capsule to be released into solution during a dissolution test (T50), and by a standard disintegration test. In general the two types of test gave closely related responses although some discrepancies existed with certain systems. For capsules containing only the drug, the value of T50 increased as the particle size of the drug decreased. The addition of lactose generally reduced the T50 value, the extent of the reduction showing greater dependence on the proportion of lactose added than its particle size. Capsule formulations containing 80% w/w of lactose had values of T50 which were independent of drug or diluent particle size. Capsule formulations containing lower proportions of lactose usually had an optimumcombination of particlesize fractions of drug and diluent for maximum drug release. The relationship between drug release and the porosity within the capsule was dependent on the particle size of the drug.