Contraceptive agents absorption

The pretreatment of rats with desipramine resulted in delayed stomach emptying and, hence, slowed absorption of phenylbutazone, oxyphenbutazone, hydrocortisone, and salicylate.On the other hand, desipramine had no apparent effect on the absorption of orally administered amphetamine or phenobarbital. In another study, the interactions of a variety of acutely and chronically administered contraceptive agents and their effect on pentobarbital narcosis in the rat, as well as on certain metabolic transformations in vitro, were examined. Medroxyprogesterone, alone or in combination with ethynylestradiol, stimulated the metabolism of 7nitroanisole, aminopyrine, and aniline in vitro, although these effects cure not as marked as those seen with well-known Inducers such as phenobarbital and pesticides. 

Many drugs interact with folate to affect its absorption, antagonize its biochemical activity, or increase its loss from the body. These drugs include ethanol, phenytoin, and oral contraceptives. Salicylates can compete with foUc acid for plasma protein binding. Methotrexate, a cytotoxic agent, is a folate antagonist that inhibits the biosynthesis of this coenzyme. 

---