Australia's medicines authority has ordered the manufacturer of a controversial sleeping pill to upgrade its warning about mixing the pills with alcohol following reports of bizarre and dangerous behaviour.

More than 500 complaints about Stilnox have been made to the national drug hotline, including reports of sleepwalkers crashing cars, falling off balconies, smoking, painting and having sex after popping a pill.

But it has agreed to a request from the Therapeutic Goods Administration (TGA) to upgrade the current warning about mixing the medicine with alcohol.

"We will amend the product information as requested by the TGA even though the potential adverse events with alcohol are already described in the current... patient information," Sanofi-aventis medical director Dr Gordon Hirsch said in a statement on Thursday.

Dr Hirsch said it was difficult to determine with certainty whether the pill had caused the bizarre sleep-related behaviour or if it was spontaneous or resulted from an underlying condition.

"The potential for complex sleep-related behaviour including sleepwalking, as well as hallucinations and amnesia is already reflected in the product information and the consumer medicines information," he said, adding that available evidence suggested the adverse events were uncommon.

The upgrade comes as Australian lawyers report being approached by several people wanting to take action against the pharmaceutical company following adverse reactions to the pills.

Slater and Gordon partner Tim Hammond said his law firm was trawling event reports for "a number" of prospective clients affected by the prescription medication.

Senior pharmacist Geraldine Moses said most involved home sleepwalkers who had woken in the morning "with cuts and bruises and no idea what's happened".

And earlier this week, a court heard one of two former NSW policemen who violently robbed a Brisbane hotel of more than $63,000 had been taking Stilnox.

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