Rifampin inductive effect

Rifampin Induction of hepatic microsomal drug-metabolizing enzymes. Corticosteroids [P] Increased corticosteroid hepatic metabolism reduced corticosteroid effect. 

Lu C, Li AP (2001) Species comparison in P450 induction effects of dexamethasone, omeprazole and rifampin on P450 isoforms 1A and 3A in primary hepatocytes from man, Sprague-Dawley rat, minipig and beagle dog. Chem. Biol. Interact 134 271-281... 

Rifampin. Source, antibacterial activity, and routes of administration are described on p. 274. Albeit mostly well tolerated, this drug may cause several adverse effects including hepatic damage, hypersensitivity with flu-like symptoms, disconcerting but harmless red/orange discoloration of body fluids, and enzyme induction (failure of oral Liillmann, Color Atlas of Pharmacology... 

Barbiturates and rifampin cause a marked decrease of the anticoagulant effect by induction of the hepatic enzymes that transform racemic warfarin. Cholestyramine binds warfarin in the intestine and reduces its absorption and bioavailability. 

Other CYP3A4 inducers have also been reported to exert a pronounced effect on oral midazolam AUC (78), presumably through induction of intestinal and hepatic CYP3A4. For example, administration of phenytoin and carba-mazepine led to a 94% reduction in midazolam AUC compared with an untreated control population. Induction of CYP3A by St. John s wort, a widely used herbal supplement for the treatment of mild to moderate depression, has also attracted considerable interest. The major bioactive ingredient of St. John s wort, hyperforin, is a very potent in vitro activator of hPXR (79,80). Several groups have investigated induction of midazolam clearance by St. John s wort (81-83). As in the case of rifampin, clearance of oral midazolam... 

Tuberculosis is another medical condition that is highly prevalent in Hispanics (Bloch et al. 1994). In contrast to the CYP inhibitory effects seen with HIV antivirals, treatment with the antituberculin drug rifampin appears to bring about CYP enzyme induction. This enzyme induction by rifampin is thought to account for the lack of response to concurrently prescribed antipsychotics in patients being treated for both psychotic disorders and tuberculosis (Li et al. 1997). 

---