Moderate
Digoxin × Rifampicin
Cardiac glycosides (digitalis)×Antituberculous antibiotic
Mechanism
Rifampicin induces enterocyte P-glycoprotein. Digoxin bioavailability falls by 30%, levels drop — risking loss of rate control in atrial fibrillation or worsening of chronic heart failure.
Symptoms
Return of underlying disease: tachycardia in atrial fibrillation, dyspnoea and oedema in chronic heart failure. After rifampicin stops, digoxin levels may rise sharply.
Management
On the combination, check digoxin levels at 2 and 4 weeks after rifampicin start and 2 weeks after rifampicin stops. Digoxin dose is usually raised by 25–50% during rifampicin and returned to baseline afterward. In atrial fibrillation, consider adding a beta-blocker (bisoprolol, metoprolol) for rate control.