Major
Amlodipine × Rifampicin
Calcium channel blockers (dihydropyridines)×Antituberculous antibiotic
Mechanism
Rifampicin strongly induces CYP3A4 – the main amlodipine metabolic route. Amlodipine plasma levels fall by 80%; the antihypertensive effect practically disappears.
Symptoms
Blood pressure returns to baseline or higher, headache. In angina, episodes reappear. Symptoms develop 1–2 weeks after starting rifampicin.
Management
During anti-TB therapy, replace amlodipine with an ACE-I (enalapril) or a diuretic (hydrochlorothiazide) – their metabolism is less affected by rifampicin. Induction persists for 2 weeks after rifampicin stops – reintroduce amlodipine gradually.
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.