Menses induction in rhesus monkeys using a controlled-release vaginal delivery system containing (15S)15-methyl prostaglandin F2α methyl ester

Abstract

Polymeric controlled-release vaginal delivery systems were designed for (15S)15-methyl prostaglandin (PG)F2 alpha methyl ester (carboprost methyl). The drug was incorporated into a highly permeable reservoir membrane that was bound to a relatively nonpermeable support membrane. The rate of drug release was controlled by coating the reservoir membrane with a less permeable rate-controlling membrane. Vaginal devices were prepared with in vitro steady-state release rates from 5 to 180 microgram/hour. The release curves were characterized by an initial, transient rapid release of the drug, followed by a linear zero-order release phase. Pregnancy was terminated in rhesus monkeys following a 24-hour treatment with vaginal devices having release rates of carboprost methyl of 45 microgram/hour or greater. Successful menses induction was associated with peripheral plasma concentrations of (15S)15-methyl PGF2 alpha between 2000 and 3000 pg/ml. Peripheral plasma concentrations of progesterone declined very rapidly to less than 1.0 ng/ml in monkeys in which pregnancy was terminated. These studies demonstrate the feasibility of manufacturing controlled-release vaginal delivery systems containing carboprost methyl for use in early pregnancy termination.