Zolpidem ('Stilnox')

The TGA has on 21 February 2008 imposed a boxed warning in the product information documents for medicines containing zolpidem. This follows continuing Australian reporting of bizarre and sometimes dangerous sleep related behaviours such as sleep walking and sleep driving in some users of zolpidem.

A boxed warning is a succinct warning statement printed at the start of the approved product information, designed to alert prescribers to an important safety issue with a medicine. The warning is highlighted by a bold black surround or "box". The wording of the boxed warning for zolpidem is "Zolpidem may be associated with potentially dangerous complex sleep-related behaviours which may include sleep walking, sleep driving and other bizarre behaviours. Zolpidem is not to be taken with alcohol. Caution is needed with other CNS depressant drugs. Limit use to four weeks maximum under close medical supervision."

Up to 4 January 2008, 1032 Australian reports of suspected reactions to zolpidem products have been entered into the TGA's Adverse Reactions database. More than two thirds of these reports (687) have been received in the last twelve months. 394 of the 1032 reports included mention of abnormal sleep related events including sleep-walking, sleep-eating and sleep driving. 103 reports (10% of all reports) included mention of sleep driving.

The very marked increase in reporting followed the publication of the February 2007 Australian Adverse Drug Reactions Bulletin which reminded prescribers of an association found between zolpidem and adverse neurological and psychiatric reactions, including changes in behaviour and mental state as well as specific effects such as sleep walking, and undertaking strange and potentially dangerous behaviours while apparently asleep. These effects are not limited to initial doses and can manifest for the first time after periods of apparently uneventful use.

As a response to these observed adverse effects, significant changes were made by sponsors to the Product Information (PI) and Consumer Medicine Information (CMI) documents for products containing zolpidem.

The updated CMI information about side effects of zolpidem includes:

• "Less common adverse effects include:
  • Unexpected changes in behaviour. These have included rage reactions, worsened insomnia, confusion, agitation, hallucinations and other forms of unwanted behaviour.
  • Sleep walking, driving motor vehicles and other unusual and on some occasions dangerous behaviours whilst apparently asleep. These have also included preparing and eating food, making phone calls or having sexual intercourse. People experiencing these effects have had no memory of the events."

It is also noted that such side effects can occur at therapeutic doses, without concomitant intake of alcohol and that alcohol intake heightens the risk of such side effects.

TGA required that packs be labelled with a warning about alcohol and that the pack sizes of zolpidem products be reduced such that, from 31st December 2007, no packs containing greater than 14 tablets have been distributed in Australia by sponsors. This step was taken on the advice of the Australian Drug Evaluation Committee with the intention of reducing exposure to the risk of these worrying and potentially dangerous adverse effects. The TGA encourages doctors not to prescribe and pharmacists not to dispense more than a single pack at one time.

The TGA wrote to the organisations representing doctors and pharmacists seeking their aid in bring these matters to the attention of their members.

The TGA also referred the status of zolpidem to NDPSC and had been awaiting its decision before taking any additional regulatory steps. The TGA's decision to apply a boxed warning follows the decision of the National Drugs and Poisons Scheduling Committee not to restrict access to zolpidem by moving it from Schedule 4 (prescription medicines) to Schedule 8 of the Standard for the Uniform Scheduling of Drugs and Poisons (medicines subject to potential abuse or illegal use). The TGA notes that NDPSC intends to keep a watching brief on this issue.

The TGA remains concerned about reports of adverse reactions with zolpidem use and continues to work with its expert advisory committees, international regulatory authorities, healthcare professionals, consumers and the companies providing zolpidem in Australia to closely monitor the safety of this medicine.

As with any medicine, healthcare professionals and patients must assess the risks and benefits of use in their individual clinical situation. If, after consideration of the risks of adverse events associated with zolpidem, the decision is made to use zolpidem patients should do so for as short a period as possible, at the lowest dose possible.

Should patients have any questions or concerns about taking this medication, they should discuss this in the first instance with their treating doctor.

Zolpidem is available in Australia in products with the following trade names:

• Stilnox and Stilnox CR
• Dormizol and Dormizol CR
• Stilnoxium CR
• Zolpidem Dakota
• Zolpidem Hexal
• Zolpidem Sandoz
• Zolpibell
• Zolpidem-DP
• Synthon Zolpidem
• Zolpixdem-Ac
• Somidem
• Stildem
• Zolpidem Pharmacor
• Genrx Zolpidem
• Chemmart Zolpidem
• TerryWhite Zolpidem
• Apo-Zolpidem