Major
diltiazem × Rifampicin
Calcium channel blocker, non-DHP (benzothiazepine derivative)×Antituberculous antibiotic
Mechanism
Rifampicin is the most potent available CYP3A4 inducer. Diltiazem plasma levels fall 5- to 10-fold. The antianginal and antihypertensive effect practically disappears.
Symptoms
Return of hypertension, anginal episodes in ischaemic heart disease. Rate control in atrial fibrillation is lost.
Management
During anti-TB therapy, replace diltiazem with amlodipine (at higher than usual dose, since induction also affects it) or an ACE-I + beta-blocker. After rifampicin stops, induction persists for 2 weeks.
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.