Oral contraceptives microsomal enzyme

Rifampin is known to induce the hepatic microsomal enzymes that metabolize various drugs such as acetaminophen, oral anticoagulants, barbiturates, benzodiazepines, beta blockers, chloramphenicol, clofibrate, oral contraceptives, corticosteroids, cyclosporine, disopyramide, estrogens, hydantoins, mexiletine, quinidine, sulfones, sulfonylureas, theophyllines, tocainide, verapamil, digoxin, enalapril, morphine, nifedipine, ondansetron, progestins, protease inhibitors, buspirone, delavirdine, doxycycline, fluoroquinolones, losartan, macrolides, sulfonylureas, tacrolimus, thyroid hormones, TCAs, zolpidem, zidovudine, and ketoconazole. The therapeutic effects of these drugs may be decreased. 

Carbamazepine is a hepatic microsomal enzyme inducer and therefore will lower the serum concentration of a wide variety of drugs given concurrently. These include the antiepileptic drugs phenytoin, primidone, valproate, ethosuximide and clonazepam. In addition, carbamazepine can compromise the therapeutic effects of oral contraceptives, oral anticoagulants, beta-blockers, haloperidol and theophylline. 

It has been suggested that the increase of serum triglyceride values seen during oral contraceptive medication is due to a hepatic microsomal enzyme induction, involving... 

In animal experiments oral contraceptives have been shown to alter the activity of the liver microsomal enzymes involved in drug metabolism (132 ). This is not unexpected since oral contraceptives are themselves metabolized by these enzymes. From animal experiments, however, it is difficult to draw any conclusions as to what may happen in man. Carteref al. (120 ) stress that there is an absolute difference in the effect of oral contraceptives on rats and humans. It is apparent that before an animal model for oral contraceptives in humans can be reliably used, the correct drug doses, species, sex, and the age of the animals need to be established. Thus, although extensive animal work has been performed, we must in the clinical situation fall back on the data obtained in man. 

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