Influence of species specificity on gastric emptying rate and blood levels of carisoprodol

Summary The simultaneous administration of propyphenazone and carisoprodol in fixed ratio to rats and mice results in the disappearance of the myorelaxant activity of carisoprodol in the former species when the compounds are administered by oral, but not by intraperitoneal route. This effect is related to decreased intestinal availability of carisoprodol, due to the inhibition of gastric emptying rate by propyphenazone. In mice, an extremely rapid gastric emptying rate allows a substantial amount of carisoprodol to pass into the duodenum before the effect of propyphenazone takes place.