[Acute delirium, probably precipitated by clarithromycin]

Clarithromycin is a relatively new antibiotic with many applications. Its frequent use explains why side-effects previously reported seldom now become clear. Two patients, a man aged 74 and a woman aged 56 years, developed delirium after treatment with clarithromycin as part of eradication treatment of Helicobacter pylori, presumably as a result of an ideosyncratic reaction to the clarithromycin. Preclinical and clinical investigations did not reveal side effects on the central nervous system. By now the appearance of a delirium presumably related to the use of clarithromycin has been described in several patients. Furthermore some patients had a positive rechallenge. Finally, 17 reports on psychiatric side effects, of which 7 were delirium, after the use of clarithromycin reached the Netherlands Pharmacovigilance Foundation (Lareb). This combination of facts makes a causal relationship probable.