Fixed Drug Eruption Induced by Combined Administration of Metronidazole and Ciprofloxacin

Abstract

Fixed drug eruption is a localised cutaneous adverse drug reaction characterised by well-defined erythematous or violaceous lesions that may recur at the same anatomical site after re-exposure to the suspected medication. Antibiotics are recognised causes of fixed drug eruption, although reports involving combined exposure to metronidazole and ciprofloxacin remain uncommon. This case report describes a 50-year-old male patient who presented with loose stools for three days, low-grade fever, vomiting, dry cough, dehydration, pre-renal acute kidney injury and hyperkalaemia. He was treated with intravenous ciprofloxacin 200 mg twice daily and intravenous metronidazole 500 mg three times daily, with supportive therapy including intravenous fluids and symptomatic medications. After three days of treatment, he developed multiple well-defined erythematous macules over both hands and legs, associated with mild itching and burning sensation. There was no mucosal involvement or systemic deterioration. Based on the temporal association with antibiotic administration and the morphology of the lesions, fixed drug eruption was considered. The suspected antibiotics were discontinued, and the patient was managed with topical corticosteroid therapy and intravenous antihistamine. The lesions gradually improved, leaving residual post-inflammatory hyperpigmentation. The Naranjo adverse drug reaction probability scale score was 5, supporting a probable adverse drug reaction. This case emphasises the need to consider fixed drug eruption in patients who develop localised cutaneous lesions after antibiotic exposure and to document suspected drug reactions carefully to reduce the risk of recurrence.