A case of variant angina exacerbated by administration of rifampicin.

Rifampicin, an antituberculosis agent, is known to be a potent inducer of microsomal drug-metabolizing enzymes in the liver. Elimination or clearance of many drugs has been reported to be enhanced, and their effectiveness reduced; however, no report in the literature has dealt with the interaction between rifampicin and dihydropiridine calcium entry-blocking drugs such as nifedipine. We present here evidence for the possible interaction between rifampicin and nifedipine in a patient with angina pectoris, which was exacerbated during coadministration or rechallenge with rifampicin. The peak plasma level and area under the curve were reduced and the apparent oral clearance of nifedipine was increased by rifampicin, suggesting that rifampicin enhanced the elimination of nifedipine via induction of a hepatic microsomal drug-metabolizing enzyme, as has been reported on other drugs widely metabolized in the liver.