ModerateCalcium channel blockers (dihydropyridines)×Calcium channel blocker, non-DHP (benzothiazepine derivative)
Updated · Methodology
Mechanism
Diltiazem is a moderate CYP3A4 inhibitor (diltiazem SmPC), and CYP3A4 takes part in amlodipine metabolism. In older patients with hypertension, diltiazem 180 mg a day increased systemic exposure to amlodipine 5 mg by 60% (US Food and Drug Administration (FDA) amlodipine label). Both drugs lower blood pressure, and their effects add up when they are taken together.
Symptoms
Lower blood pressure, dizziness on standing, fatigue, leg oedema. Older patients: fall risk.
Management
The combination is acceptable with monitoring. Clinical monitoring and a lower amlodipine dose may be needed, and the effect can be stronger in older patients (amlodipine SmPC). Watch for signs of hypotension and oedema and use them to decide whether the amlodipine dose should change (US Food and Drug Administration (FDA) amlodipine label).
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Sources
- AEMPS: Ficha técnica: Amlodipino (nº registro 65461), sección 4.5 (2025)– AEMPS, CIMA, nº registro 65461, revisión 08/2025, sección 4.5
- FDA: Norvasc (amlodipine) prescribing information (2023)– FDA label, DailyMed setid 7367289c-b0b0-466a-83e2-558e2985c29f, revised 02/2023, sections 7.1 and 12.3
- AEMPS: Ficha técnica: Diltiazem, Masdil Retard 120 mg (nº registro 58483), sección 4.5 (2025)– AEMPS, CIMA, nº registro 58483, revisión 03/2025, sección 4.5
- FDA: Cardizem CD (diltiazem) prescribing information (2025)– FDA label, DailyMed setid 1042fa13-e6af-46b9-8008-6c941f0978b1, revised 12/2025, PRECAUTIONS: Drug Interactions