Moderate
Probable
Descripción
Cephalexin may enhance the anticoagulant effect of warfarin, with case reports describing INR elevation during concurrent therapy, likely through disruption of vitamin K-producing gut flora.
Mecanismo
Broad-spectrum antibiotics including cephalexin reduce intestinal bacteria that synthesise menaquinones (vitamin K2), decreasing vitamin K availability and augmenting warfarin's anticoagulant effect.
Relevancia clínica
Case reports and observational data link cephalosporin use to supratherapeutic INR values; the interaction is unpredictable in magnitude.
Manejo clínico
Monitor INR within 3–5 days of starting cephalexin in anticoagulated patients; adjust warfarin dose if INR rises above target range.