Clarithromycin-Induced Psychosis: When Is Delirium Not Delirium?

Clarithromycin-induced psychosis is a rare phenomenon; however, over the previous two decades, there has been increasing evidence linking psychotic episodes to the use of clarithromycin. The exact aetiology of this remains unclear, but several key hypotheses have arisen, including gamma-aminobutyric acid type A receptor (GABA-A) antagonism and active clarithromycin metabolites altering brain neurotransmitters such as glutamate. Recent evidence describes a broad range of symptoms, including delusions and catatonic states. Prior psychiatric comorbidities are a substantial risk factor. This case report describes the development of clarithromycin-induced psychosis in an 86-year-old patient with no prior psychiatric medical history, cognitive or functional impairment, and no other pathology found accountable for this neuropsychiatric disturbance. By acknowledging this rare adverse effect of clarithromycin and discontinuing the drug, the patient's psychotic symptoms resolved within 24 hours. Given the widespread use of clarithromycin, this case report demonstrates the importance of being aware of its rare neuropsychiatric adverse effects to diagnose this relatively unusual presentation.