A Case Report of Zolpidem-Induced Somnambulism

Sir: The physiology of sleep, memory, awareness, and arousal can be influenced by different drugs.¹ Zolpidem tartrate is a nonbenzodiazepine hypnotic agent of the imid-azopyridine group with a rapid onset and short duration of action. Its side effect profile is milder than those of benzodiazepines and barbiturates used for treating insomnia.² To our knowledge, there are 5 published articles^3–7 related to zolpidem-induced somnambulism. Somnambulism, or sleepwalking, could be dangerous due to the possibility of accidental injury. Here, we present a case of somnambulism associated with zolpidem use.

Case report. Mr. A, a 19-year-old white man, had a history of and current diagnoses of DSM-IV schizoaffective disorder and impulse-control disorder. The patient lived with his parents and a younger brother. He worked as a volunteer at a university hospital and had received a general equivalency diploma. Mr. A had no current or past history of substance abuse and did not smoke or drink alcohol. His medical history was unremarkable. The patient had a history of 2 psychiatric hospitalizations for worsening of his symptoms. He had no personal or family history of sleepwalking.

In the past, olanzapine and paroxetine had been tried without successful results. Mr. A was stable on his medications, which included aripiprazole 15 mg once per day, venlafaxine extended release 150 mg once per day, and quetiapine 50 mg once per day. He received no other medications, including herbal supplements.

During the course of his treatment, Mr. A began complaining of insomnia, for which brief zolpidem treatment was prescribed. He was started on treatment with zolpidem 10 mg orally at bedtime on an as-needed basis for insomnia. Within a few days of the initiation of zolpidem treatment, the patient's family noticed the patient waking up in the middle of night and walking into their room with a staring expression and some incoherent speech. The patient had no memory of this event in the morning. This sleepwalking episode was attributed to zolpidem, as no medication change was made besides initiating zolpidem and the patient had no history of such episodes in the past. Zolpidem treatment was stopped, and since then, no complaints of sleepwalking have been reported.

Somnambulism, or sleepwalking, generally occurs during stages 3 and 4 of slow-wave sleep.⁸ During an episode of somnambulism, the normal arousal mechanism is altered, which results in partial arousal without full consciousness.⁹ Electroencephalographic changes associated with the use of zolpidem include suppression of REM sleep.¹⁰ It has been suggested that some drugs produce a physiologic state during slow-wave sleep that can present clinically as somnambulism.⁸ A definitive diagnosis of somnambulism usually requires all-night sleep recordings,⁸ which were not performed on our patient. We suggest that when seeking an etiology of somnambulism in a patient, a careful review of the patient's current medications should be performed.