Relationship between Polymorphism and Bioavailability of Amobarbital in the Rabbit

Abstract

The effect of the polymorphic form of amobarbital on its bioavailability was examined by measurement of the dissolution rate and in vivo absorption of two forms (Form I and Form II). The dissolution rate of Form II was faster than that of Form I. In in vivo absorption experiments using rabbits, two crystal forms of amobarbital were administered orally and the resulting blood level-time curves were compared with the dissolution rates. It appeared that the polymorphic form of the drug appreciably affected the absorption process from the digestive tract. Hydroxyamobarbital was confirmed to be the main metabolite of amobarbital. © 1981, The Pharmaceutical Society of Japan. All rights reserved.