Formulation and Pharmacokinetic Studies of Acyclovir Controlled-Release Capsules

Acyclovir controlled-release capsules (CRCs) were prepared by a three-step process: 1] melt granulation of acyclovir; 2] coating of granules with ethylcellulose; 3] incorporation of coated granules into hard gelatin capsules. In vitro release experiments showed that the main factors affecting the release rate were the mean particle size of the acyclovir raw material and the amount of coating material applied. Release of acyclovir from the capsules was in accordance with the Higuchi equation. Pharmacokinetic studies in dogs after oral administration of acyclovir controlled-release capsules showed that the formulation was successful in providing slow release of acyclovir and was superior to a commercially available controlled-release formulation.