Rifampicin reverses nicardipine effect inducing uncontrolled essential hypertension

Dihydropyridine calcium-channel blockers are a known substrate for the cytochrome P450 isoform 3A4. Rifampicin, an antitubercular agent, is one of the most potent inducers of hepatic and intestinal CYP3A4 thus increasing dihydropyridine metabolism. We report a case of a 67-year-old hypertensive female treated with a four-drug antihypertensive regimen including a dihydropyridine (nicardipine 50 mg bid), who was admitted for septic arthritis of the knee requiring antibiotic treatment with teicoplanin 400 mg od and rifampicin 600 mg bid. Six days after rifampicin initiation, she presented with Posterior Reversible Encephalopathy Syndrome due to uncontrolled hypertension. We hypothesized that disequilibrium of previously controlled hypertension was partially due to nicardipine ineffectiveness. Plasma nicardipine concentration was assessed through high-performance liquid chromatography 5 hours after coadministration of the two drugs and proved undetectable.