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Abstract

Drug interactions are a frequent cause of Emergency Department (ED) visits and may pose a significant threat to patients, leading to reduced therapeutic efficacy or drug toxicity. Early recognition of these interactions is essential to prevent adverse clinical outcomes. A 66-year-old man with a history of hypertension, smoking and epilepsy, treated with olmesartan, levetiracetam, and carbamazepine. Following a diagnosis of Helicobacter pylori infection, he was started on an eradication regimen including esomeprazole, amoxicillin, metronidazole and clarithromycin. On the fifth day of treatment, he developed gait imbalance, slurred speech, dizziness and motor incoordination. Due to suspicion of acute ischemic stroke, he was referred to the ED. Cranial computed tomography was normal, while laboratory tests revealed toxic serum levels of carbamazepine. Clarithromycin acts as a potent inhibitor of the CYP3A4 isoenzyme, reducing the hepatic metabolism of carbamazepine and increasing its serum levels. This combination can cause neurological toxicity with a presentation similar to a stroke, and should therefore be avoided.