A patient presents with spontaneous gingival bleeding. Which medication is the most likely cause?

Warfarin (a vitamin K antagonist anticoagulant) prolongs clotting and is a classic cause of gingival/mucosal bleeding, especially if the INR is supratherapeutic.Other options: Amoxicillin, lisinopril, and metformin do not characteristically cause bleeding (though some antihypertensives/CCBs cause gingival overgrowth, not bleeding).Key exam takeaway: Unexplained gingival/mucosal bleeding in a medicated patient: think anticoagulants (check INR for warfarin).