ABSTRACT
This chapter examines the application of general pharmacokinetic considerations to in vivo evaluation of microencapsulated drugs intended for obtaining sustained release by oral administration. Applications of microencapsulation considered to be of special promise for new or improved therapy involve some type of prolonged action and targeting of medications. Microcapsules containing drugs should be bioequivalent to the reference standard dosage form used in the clinical studies which established the dose or dosage regimen for that drug. Market limitations in the number of microencapsulated drug dosage forms at the present time probably reflect the inability of clinical advantages to compensate for economic factors involved in large-scale manufacturing. A relatively simple pharmacokinetic model is introduced which allows for the gastric emptying and intestinal-transit rates of a drug itself and a solid-state drug contained in microcapsules. Preparations which release a drug more slowly are likely to result in an unacceptably low bioavailability.
