Antimicrobial associated encephalopathy (AAE) is a well-documented, though under recognised, adverse event associated with antimicrobial use. Clinical manifestations of AAE are varied, ranging from myoclonus and seizure to an encephalopathy with cerebellar signs. The phenotypic presentation of the encephalopathy syndrome is, in general, governed by the antimicrobial in question. Given its apparent rarity in everyday clinical practice, awareness of AAE is crucial for physicians. We describe a reversible encephalopathy characterised by confusion, myoclonus and stupor in a 76 year old gentleman on antimicrobial therapy for a peri-rectal abscess.