edoxaban and clarithromycin

Clarithromycin inhibits P-glycoprotein (P-gp) and CYP3A4. Edoxaban is a substrate of P-gp, which limits its absorption and promotes its renal elimination. Inhibition of P-gp by clarithromycin increases edoxaban absorption and decreases renal clearance, leading to elevated plasma concentrations. The additional CYP3A4 inhibition has a minor contributory role. The net effect is a significant increase in edoxaban exposure.

Increased edoxaban concentrations heighten the risk of serious bleeding events, including gastrointestinal haemorrhage and intracranial haemorrhage, which can be fatal. Patients may experience spontaneous bruising, epistaxis, haematuria, or prolonged bleeding from minor cuts. The risk is amplified in patients with additional predisposing factors, such as advanced age, renal impairment, or concurrent use of antiplatelets or NSAIDs.

Avoid coadministration unless the benefit clearly outweighs the risk. If unavoidable, consider reducing the edoxaban dose by half (for example, from 60 mg to 30 mg once daily). Monitor the patient closely for signs of bleeding, and assess renal function at baseline and periodically. Consider an alternative antibiotic with minimal P-gp inhibition, such as azithromycin, if clinically appropriate. Instruct the patient to seek urgent medical attention if they develop unusual bleeding.

The interaction is well-established from pharmacokinetic studies and is documented in the prescribing information for edoxaban. Co-administration with clarithromycin increases edoxaban exposure by approximately 50–80%. Although direct outcome data on bleeding events are limited, the elevated anticoagulant effect is expected to translate into increased bleeding risk.