Polymeric delivery of the active isomer of misoprostol reduces systemic availability and uterotonic activity.

SC-30249 is the active isomer of misoprostol responsible for its mucosal protective effects against nonsteroidal anti-inflammatory drugs (NSAIDS). Linkage of SC-30249 to a polybutadiene polymer results in a delivery system (SC-55307) that releases the active component only under the acidic conditions of the stomach. This approach could be used to minimize side effects and systemic availability of synthetic prostaglandins. These studies were done to determine whether uterotonic activity could be recorded after treatment with SC-55307. Female beagles were implanted with uterine strain gauge force transducers, allowed 10 days for recovery and treated with estrogen to sensitize the uterus to the actions of prostaglandins. Base-line responses were determined with SC-30249, i.v., and then a randomized series of four treatments were given: SC-30249, IG, 10 micrograms/kg; SC-55307, IG, equivalent to 30 and 100 micrograms/kg of SC-30249; and a blank polymer control. HCI was given IG to provide an acid environment in the stomach, uterine responses were obtained for up to 4 h and plasma concentrations of SC-30249 free acid was determined. No uterotonic effect was seen after a low dose of SC-55307, whereas the high dose caused a brief but statistically significant increase equal to 8.8% and 17.8% of the responses to SC-30249, i.v. and IG, respectively. Peak plasma levels of SC-30249 free acid were 176.4 +/- 17.4 and 59.5 +/- 10.6 pg/ml after SC-30249, i.v. and IG, respectively, but were only 3.9 +/- 1.7 and 15.5 +/- 6.6 pg/ml after low and high doses of SC-55307, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)