CriticalMacrolide antibiotic×First-generation antipsychotic, diphenylbutylpiperidine derivative
Updated · Methodology
Mechanism
Clarithromycin is a strong CYP3A4 inhibitor. Pimozide is 80% metabolised by CYP3A4; concentration rises 5–7 fold during co-administration. FDA Orap Section 4 strict contraindication – risk of QT prolongation, torsades de pointes and sudden cardiac death.
Symptoms
Within 3–7 days: palpitations, dizziness, syncope. ECG QTc above 500 ms, ventricular ectopy; in severe cases torsades de pointes progressing to ventricular fibrillation.
Management
Combination contraindicated. For infection in a pimozide patient use azithromycin (no CYP3A4 inhibition) or another antibiotic class (amoxicillin for typical pneumonia). If clarithromycin is needed, hold pimozide for the course and resume 7 days after the last dose.
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.
Summary of a multi-drug list →
Medicine list: everything you take in one place →
Sources
- FDA: Pimozide tablet (Par Health USA, LLC) – Prescribing Information (2011)– FDA Orap label, Section 4 Contraindications; DailyMed setid 70b079e2-a1f7-4a93-8685-d60a4d7c1280
- AEMPS: Ficha técnica: Claritromicina (nº registro 75638), sección 4.3 (2025)– AEMPS, CIMA, nº registro 75638, revisión 03/2025, sección 4.3