Moderate
Bisoprolol × Rifampicin
Selective beta-adrenergic blockers×Antituberculous antibiotic
Mechanism
Rifampicin induces CYP3A4, modestly lowering bisoprolol plasma levels (bisoprolol is metabolised 50% via CYP3A4 and 50% renally). The effect is weaker than for fully CYP-dependent beta-blockers.
Symptoms
Gradual blood pressure rise or return of anginal symptoms 2–3 weeks after starting rifampicin. In tachyarrhythmias: return of symptoms.
Management
During anti-TB therapy, increase bisoprolol by 50% with blood pressure and pulse monitoring. After rifampicin stops, taper back gradually (induction persists for 2 weeks).