Moderate
Amitriptyline × Verapamil
Tricyclic antidepressants (TCA)×Non-dihydropyridine calcium channel blocker
Mechanism
Verapamil blocks CYP3A4 (one of the amitriptyline metabolic routes). TCA plasma levels may rise slightly. Plus additive bradycardia and PR prolongation.
Symptoms
Bradycardia, postural dizziness, syncope. ECG: PR prolongation. Older patients: delirium risk.
Management
In older patients, check pulse and ECG 1–2 weeks after starting amitriptyline. Alternative calcium channel blocker without CYP effect: amlodipine (with amitriptyline's α1-blockade – see the related pair). For neuropathic pain, alternative: gabapentin or pregabalin.
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.