Eletriptan × Ritonavir

The liver breaks down eletriptan mainly through the enzyme CYP3A4, and ritonavir strongly inhibits this enzyme. The labels give no study of this exact pair. The closest guide is data on other strong CYP3A4 inhibitors. Ketoconazole 400 mg raised the eletriptan area under the curve (AUC) 5.9-fold and lengthened its half-life from 4.8 to 8.3 hours. Erythromycin 1000 mg raised the AUC 3.6-fold. Like other triptans, eletriptan can cause coronary artery spasm. The Paxlovid (nirmatrelvir with ritonavir) labels explain the contraindication by the risk of serious adverse reactions, including cardiovascular and cerebrovascular events.

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 Paxlovid labels, where ritonavir is combined with nirmatrelvir, also contraindicate it (European Medicines Agency, EMA, and FDA). The eletriptan summary of product characteristics (SmPC) says not to use eletriptan with ritonavir 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 ritonavir before giving eletriptan (eletriptan label, FDA; Paxlovid labels, EMA and FDA). The documents set no dose condition, so the contraindication also covers the low ritonavir doses used to boost other antiviral drugs, including in Paxlovid. If eletriptan has been taken during ritonavir 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).