Studies of Hie Effect of Powder Moisture Content on Drug Release from Hard Gelatin Capsules

Abstract

The in vitro dissolution of model formulations from hard gelatin capsules containing drug: diluent powder mixtures at different moisture levels has been studied. The capsules were filled to a constant porosity of 50%. to contain either sodium barbitone or barbitone in 50:50 mixture with lactose or maize starch, the latter at one of three moisture levels. In addition, capsules containing drug alone were examined. The wettability and polarity indeces of the individual powders and binary mixtures, as well as the permeability and liquid penetration rates of powder beds were also determined. The presence of either excipient was found to modify the time for 50% drug dissolution (t₅₀) compared with drug alone for all formulations examined, apart from the sodium barbitone: lactose capsules. The rate of drug dissolution was also dependent on the initial powder moisture content for the drug:starch formulations. Open storage of capsules at 20^%/75%. R.lt. generally increased t₅₀figures. The findings are discussed in terms of the nature of the surfaces of the powder particles, moisture sorption phenomena and factors such as powder bed permeability and water penetitration lates.