Major
clonidine × diltiazem
Central α2-adrenergic agonist×Calcium channel blocker, non-DHP (benzothiazepine derivative)
Mechanism
Additive bradycardia and atrioventricular (AV) block. Clonidine lowers sympathetic tone and slows conduction; diltiazem directly blocks the AV node.
Symptoms
Bradycardia (heart rate below 50/min), dizziness, syncope. ECG: first- to second-degree AV block. Older patients: fall and fracture risk.
Management
Avoid the combination, especially in older patients. Alternative calcium channel blockers in hypertension: amlodipine or nifedipine (no AV effect). Alternative to clonidine: an ACE-I or ARB with a diuretic.
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.