Carbamazepine with hepatic microsomal

Carbamazepine induces hepatic microsomal enzymes that can decrease the steady-state plasma levels of phenothiazines (reported mainly with chlorpromazine, fluphenazine, and perphenazine). Chlorpromazine and thioridazine may increase the serum levels of phenytoin due to its inhibition of hepatic mono-oxygenase activities. 

Cholestatic hepatitis may occur when drug therapy lasts longer than 10 days or repeated courses are prescribed. The hepatitis is characterized by fever, enlarged and tender liver, hyperbilirubinemia, dark urine, eosinophilia, elevated serum bilirubin, and elevated transaminase levels. Hepatitis has been associated with the estolate salt of erythromycin but not with other formulations. Although the hepatitis usually occurs 10 to 20 days after the initiation of therapy, it can occur within hours in a patient who has had such a reaction in the past. The hepatitis is believed to be the result of both a hepatotoxic effect and a hypersensitivity reaction this latter effect is reversible on withdrawal of the drug. Erythromycin and derivatives induce hepatic microsomal enzymes and interfere with the actions of various drugs, including theophylline and carbamazepine. 

Calcium-channel blockers Diltiazem and verapamil have inhibitory effects on hepatic microsomal enzymes, and so can increase serum levels of carbamazepine. Nifedipine has not been studied as well as the other calcium-channel blockers, but present data suggest that it probably does not interact significantly with carbamazepine. 

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