Griseofulvin Warfarin

Cullen SI, Catalano PM. Griseofulvin-warfarin antagonism. JAMA 1967 199(8) 582-3. 

Cullen SI and Catalano PM Griseofulvin-warfarin antagonism JAMA (1967) 199, 582-3... 

Griseofulvin is usually well tolerated. Headache is common with initiation of therapy. Hepatotoxicity (especially in patients with acute intermittent porphyria), dermatitis, and gastrointestinal distress also occur. Griseofulvin increases warfarin metabolism, and griseofulvin metabolism is increased by phenobarbital. 

Antimicrobials. Aztreonam, cefamandole, chloramphenicol, ciprofloxacin, co-trimoxazole, erythromycin, fluconazole, itraconazole, ketoconazole, metronidazole, miconazole, ofloxacin and sulphonamides (including co-trimoxazole) increase anticoagulant effect by mechanisms that include interference with warfarin or vitamin K metabolism. Rifampicin and griseofulvin accelerate warfarin metabolism (enzyme induction) and reduce its effect. Intensive broad-spectrum antimicrobials, e.g. eradication regimens for Helicobacter pylori (see p. 630), may increase sensitivity to warfarin by reducing the intestinal flora that produce vitamin K. 

Griseofulvin is deposited in the keratin precursor cells that are gradually replaced by healthy tissue. Griseofulvin has caused skin rashes, urticaria, angioneurotic edema, lupus-like syndrome, photosensitivity, and proteinuria. The serum level of griseofulvin is reduced by barbiturates and griseofulvin reduces the hypoprothrombinemic effects of warfarin and actions of oral contraceptive medications. 

Griseofulvin induces hepatic CYPs and increases metabolism of warfarin, sometimes necessitating dose adjustment it also may reduce the efficacy of low-estrogen oral contraceptive agents. 

Okino K, Weibert RT. Warfarin-griseofulvin interaction. Drug Intel Clin Pharm (1986) 20, 291-3. 

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