Lotrich Francis E, Rosen Jules, Pollock Bruce G
Department of Psychiatry, Western Psychiatric Institute and Clinic, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania 15213, USA.
Am J Geriatr Pharmacother. 2005 Mar;3(1):17-20. doi: 10.1016/j.amjopharm.2005.03.002.
Dextromethorphan is a commonly used antitussive agent that can be purchased over the counter. It is metabolized primarily by the cytochrome P450 (CYP) 2D6 isozyme. Methadone has been found to inhibit CYP2D6, indicating a potential for interaction with dextromethorphan.
An 83-year-old woman was evaluated for delirium, hypersomnia, confusion, lethargy, impaired concentration, and poor food intake. Symptoms resolved soon after discontinuing dextromethorphan.
Vulnerability to delirium was potentially caused by coadministration of methadone, which can inhibit the CYP2D6 isozyme.
Evaluation of delirium should include close investigation of the patient's medications for potential interactions with dextromethorphan.
