Zolpidem-induced CSBs refer to sleep related, amnesic, complex behaviours, with onset and termination temporally correlating to the use of Zolpidem.5,6 During these episodes the individual engages in activities while not awake and hence they do not have recollection of the same when enquired retrospectively.4,7 The commonly described Zolpidem-induced CSBs range from activities like walking, eating, cooking, cleaning, waxing, using phone and watching TV to driving and shopping.2 Certain other Zolpidem-induced CSBs include falls with serious injuries (such as intracranial haemorrhages, vertebral fractures and hip fractures), self-injuries, fatal falls, accidental overdoses, hypothermia, suicide attempts, apparent completed suicides, fatal motor vehicle collisions with the patient driving, gunshot wounds, carbon monoxide poisoning, drowning or near drowning, exposure to extreme cold temperatures leading to loss of limb, burns and homicide.5 These Zolpidem-induced CSBs have resulted in serious injuries and even death5 and thus, have forensic implications.3
CSBs can occur following first use or long-term use of Z-drugs, at recommended doses and even when taken alone or along with other central nervous system(CNS) depressants.1 Use of > 10mg daily dose, female gender, extended release formulations and drug interactions have been implicated to be associated with higher risk of next morning impairment and CSBs.2,8,9 The mechanisms underlying the occurrence of CSBs have not been clearly elucidated while the binding of Zolpidem to α2, α3 and α5 subunits at higher doses (> 10mg) has been postulated.2 Zolpidem-induced suppression of REM sleep with corresponding increase in NREM sleep and resultant increase in NREM parasomnias has also been hypothesized as one of the mechanisms.2,4,7
Certain measures taken while prescribing Zolpidem, such as informing the patient about the possible side effects and adverse events, advising not to take it at a higher than prescribed dose or frequency, asking the patient to go to bed right after the drug intake followed by staying in bed for 7 to 8 hours and to not combine it with alcohol or other sedatives, might help in reducing the chances of such adverse events.1,5
This patient had shown a complex behaviour of hiring a cab to visit a Psychiatric hospital, interacting with the doctors and getting himself admitted. He also co-operated with the in-patient management until he regained awareness of his behaviour the next morning. Such a presentation, explores the possibility of Zolpidem-induced CSB presenting as any activity that an alert, awake and conscious individual would perform, in as normal patterns as the individual would otherwise engage in. Hence, these behaviours other than being noticed to be occurring during sleep time, might not raise any suspicious until the witnesses, if any, retrospectively enquire and the patient is unable to recollect. Accompanying anterograde amnesia for the event, further plays a role in under-reporting of such instances unless the patient pursues the cause for such apparently strange happenings.
Zolpidem is commonly prescribed for insomnia by physicians across all specialities. Therefore, it is of paramount importance to take adequate measures while prescribing Zolpidem and to be aware of unusual presentations of these rare, yet potentially serious adverse events which may have forensic implications.