Visual hallucinations and amnesia associated with zolpidem triggered by fluvoxamine: a possible interaction.

Zolpidem is widely prescribed in clinical practice for the treatment of sleep disorders and it is generally considered safe and well tolerated. However, several cases of hallucinations, amnesia, and delirium associated with the use of zolpidem have been reported previously (Ansseau et al., 1992; Katz, 1995; Toner et al., 2000). We present an elderly woman who experienced visual hallucinations and amnesia associated with zolpidem triggered by fluvoxamine. The patient gave written informed consent to the publication of this letter. The patient was an 82-year-old Asian woman who came to our outpatient clinic with depressed mood, lassitude, and insomnia. She had not received any prior psychiatric treatment and had no past history of alcohol or substance abuse. After a psychiatric interview, she was diagnosed with a major depressive disorder according to DSM-IV. We prescribed 50 mg/day of fluvoxamine and 10 mg/day of zolpidem, and increased the dose of fluvoxamine to 100 mg/day after two weeks. After one and a half months on this medication, she was admitted to our hospital because her depressive symptoms had not improved. In addition to her depressed mood, lassitude, and insomnia she now also experienced suicidal thoughts. On admission we increased the dose of fluvoxamine from 50 mg two times per day to 50 mg three times per day for her depressive symptoms and maintained the prescribed dose of zolpidem (10 mg) at bedtime. Approximately 30 minutes after taking 10 mg of zolpidem at 2030 on the third day of her admission, she said confusedly, “My grandson comes and sees me. I want to go home with him.” She had experienced an episode of visual hallucination, which lasted from several minutes to half an hour almost every night. The next morning she could not remember anything of the previous night. We re-examined a blood test including glucose level, ammonia concentration, and endocrine disturbance, and conducted electroencephalography and magnetic resonance imaging of the brain. These laboratory tests showed that everything was within normal limits – there were no abnormal findings that might cause visual hallucinations and amnesia. We postulated that possible fluvoxamine–zolpidem interaction induced her visual hallucinations and amnesia, and so discontinued the zolpidem 10 mg dose at bedtime. Subsequently, her nightly visual hallucinations and amnesia disappeared. After four weeks of taking fluvoxamine 150 mg/day, her depressive symptoms ameliorated and she was discharged and able to go home. Two months