Zolpidem (Stilnox^®, Sanofi-Synthelabo) has been licensed for use in Singapore since 1993 for the treatment of severe sleep disorders in occasional insomnia and transient insomnia. It is structurally unrelated to the benzodiazepines, but has similar sedative-hypnotic actions.

Recently, the Australian Therapeutics Goods Administration (TGA) highlighted numerous domestic reports of abnormal and bizarre sleep-related behaviours associated with zolpidem.

In 2002, the TGA noted that an approximate of 75% of the reports received for zolpidem described one or more neurological or psychiatric reactions (e.g. visual hallucinations, confusion, depression and amnesia). There were also numerous reports describing sleeping or falling asleep and 16 reports of sleep-walking describing inappropriate or automatic behaviour while asleep, including binge eating and house painting.

TGA subsequently strengthened the product labeling to warn of abnormal sleep-related behaviour associated with zolpidem and that zolpidem is not to be taken with alcohol. The TGA has recommended that prescribers be alert to this fact and to warn their patients (especially first-time users) of these effects. TGA will also be updating the package insert of another similar non-benzodiazepine, zopiclone to warn of these unusual adverse effects.

The US Food and Drugs Administration (FDA) has after reviewing the available post-marketing adverse event information, requested for all sedative-hypnotics (13 in total) in the US to strengthen their product labelling to warn of risks of complex sleep-related behaviours, which may include sleep-driving, making phone calls, and preparing and eating food while asleep.

Recently, HSA has received four reports – two of abnormal sleep-related events, one of amnesia with a “dream-like” state and one of sleep-walking associated with the use of zolpidem. The ADRs were reported in three Chinese females and a Eurasian female with an age range of 40 to 76 years old and who have been taking zolpidem for 22 to 68 days before the onset of the ADR. Although the presence of confounding factors such as the use of concomitant drugs have made causality assessment difficult, the association between the events and zolpidem cannot be ruled out. In addition, the use of higher than recommended dosages could be contributory to the occurrence of the event.