9-Carboxymethoxymethylguanine

9-Carboxymethoxymethylguanine (CMMG) is a compound which is known as the principal metabolite of the antiviral drug acyclovir (and its prodrug valacyclovir), and has been suggested as the causative agent in the neuropsychiatric side effects sometimes associated with these drugs. These are mainly suffered by patients with renal failure or otherwise decreased kidney function, and can include psychotic reactions, hallucinations, and rarely more complex disorders such as Cotard delusion. Patients suffering these symptoms following acyclovir treatment were found to have much higher levels of CMMG than normal, and since this is the first time Cotard delusion has been linked to a drug as a side effect, this discovery may be useful in the study of Cotard delusion and its treatment.