A 32-year-old woman with community-acquired pneumonia is started on amoxicillin-clavulanate. After 48 hours of therapy, she develops a diffuse maculopapular rash sparing the palms and soles, with fever (38.5°C) and mild hepatic transaminitis (ALT 120 U/L). She denies respiratory distress or angioedema. What is the most appropriate next step in management?