Clarithromycin × Eletriptan

The liver breaks down eletriptan mainly through the enzyme CYP3A4, and clarithromycin strongly inhibits this enzyme. According to its own prescribing information, clarithromycin can raise the levels of drugs broken down by CYP3A enzymes and increase or prolong their adverse effects. The labels give no study of this exact pair. The closest guide is erythromycin, another macrolide antibiotic. At 1000 mg, it raised the eletriptan area under the curve (AUC) 3.6-fold and lengthened its half-life from 4.6 to 7.1 hours. Ketoconazole 400 mg raised the AUC 5.9-fold. Like other triptans, eletriptan can cause coronary artery spasm. In clinical trials, doses of 60 mg or more caused short-lived rises in blood pressure.

Tightness, pain or pressure in the chest, throat, neck and jaw is common after eletriptan. It is usually not cardiac but can be a sign of coronary artery spasm. Myocardial infarction, ventricular tachycardia and ventricular fibrillation have been reported within a few hours of triptan use, sometimes in people without known heart disease. Rarely, blood pressure rises sharply, even to a hypertensive crisis. Spasm of other arteries can cause Raynaud's syndrome or bowel ischaemia with abdominal pain and bloody diarrhoea. Stroke and brain haemorrhage have occurred after triptans.

The combination is contraindicated (eletriptan label, US Food and Drug Administration, FDA). The eletriptan summary of product characteristics (SmPC) says not to use eletriptan with clarithromycin or other strong inhibitors of the enzyme CYP3A4 (Spanish Agency of Medicines and Medical Devices, AEMPS). Wait at least 72 hours after the last dose of clarithromycin before giving eletriptan (eletriptan label, FDA). If eletriptan has been taken during clarithromycin treatment and chest pain or tightness suggesting cardiac ischaemia appears, give no further doses and evaluate the heart (eletriptan SmPC, AEMPS). Stop eletriptan if arrhythmias occur and monitor blood pressure during treatment (eletriptan label, FDA). If signs of spasm in other arteries appear, such as abdominal pain with blood in the stool or white, cold fingers, rule out vasospasm before the next dose (eletriptan label, FDA).