bisoprolol and verapamil

Pharmacodynamic interaction. Both bisoprolol (beta-1 blocker) and verapamil (non-dihydropyridine calcium channel blocker) have negative chronotropic, inotropic and dromotropic effects. They act synergistically to slow sinus node automaticity, prolong AV nodal conduction and depress myocardial contractility.

Additive cardiodepressant effects can result in bradycardia, hypotension, AV block and worsening of heart failure. The risk is highest in patients with pre-existing conduction abnormalities, left ventricular dysfunction or those receiving other negative inotropic drugs. Symptoms may include dizziness, fatigue and syncope.

Avoid co-prescription where possible. If combination is necessary, use cautiously with lower doses of both agents. Monitor heart rate, blood pressure and ECG at baseline and after any dose change. Consider switching to a dihydropyridine calcium channel blocker if rate control is not the primary goal. Intravenous verapamil should be avoided in patients taking bisoprolol.

Well-established interaction. Numerous guidelines, drug labels and clinical case reports describe serious adverse effects. The combination is generally considered contraindicated or to be avoided when possible.