sleeping drug which actor Heath Ledger had admitted taking has been linked to six deaths in the UK.
Figures obtained by the Sunday Herald have revealed that six fatal suspected adverse drug reactions to zolpidem have been reported to Britain's medicines watchdog since 2001.
Almost 200 further incidents of adverse reactions, ranging from psychiatric and cardiac disorders to "injuries" and eye disorders have also been reported to the Medicines and Healthcare products Regulatory Agency (MHRA).
Ledger was found dead by his housekeeper at his New York apartment last Tuesday. Pills were found near his body and Ledger recently admitted taking the prescription drug Ambien - the trade name of zolpidem in America - to combat insomnia.
Results of a postmortem examination last week on the 28-year-old actor, who had won acclaim in films such as Brokeback Mountain, are inconclusive, but there has been speculation he died from an accidental overdose of sleeping pills.
This prompted movie star Jack Nicholson to say the tragedy could be a warning about the dangers of certain sleeping pills. Nicholson said he had taken Ambien and it had serious side effects.
During a promotional visit to London for his latest film he said: "I warn people about Ambien. I almost drove off a cliff once. I don't take sleeping pills but somebody said, take this, it's mild'.
"I got a call in the middle of the night, kind of an emergency, and I almost drove off a cliff 50 yards from my house. I live up in the mountains in Aspen. It's something to warn people about."
The figures from the MHRA show the incidents recorded under its "yellow card" scheme, which doctors use to alert the agency to patients suffering side-effects to a drug. Health professionals and patients report reactions on a voluntary basis - companies are legally obliged to do so - and it is designed to act as an early warning system to flag up any previously unrecognised problems.
A total of 197 suspected adverse drug reactions have been reported to date in connection with zolpidem - which is marketed as Stilnoct in the UK - the majority of which were categorised as psychiatric disorders.
Six cases of deaths linked to a suspected adverse reaction to the drug were also recorded - three involving psychiatric disorders, with the rest categorised as general disorders, injuries and vascular disorders.
Last year research by Australia's Federal Health Department linked zolpidem to a series of incidents of strange behaviour, including a woman who painted her front door while still asleep.
Problems involving zolpidem have emerged in America, where some people have been injured by cars driven by people under the influence of the drug.
A spokesman for the MHRA said the safety of zolpidem has been "carefully monitored" and product information had been updated to include warnings of psychiatric adverse effects.
A spokesman for Sanofi Aventis, which makes Stilnoct, said it could not comment on the MHRA figures, but said when taken as prescribed, the drug was "generally well tolerated".