A drug meant for ceasing cigarette cravings will carry warnings of links with suicidal thoughts when it is launched in Australia in January.
Packs of Champix tablets will contain extra information warning that some patients have gone through depression, agitation and suicidal thoughts while taking the drug.
Even the doctors have been mailed letters updating them of the changes, fuelled by adverse effects reported to US authorities.
Under the Pharmaceutical Benefits Scheme (PBS) the smokers will be able to get one three-month treatment course a year
The Therapeutic Goods Administration (TGA) said that it had reviewed reports submitted to the US Food and Drug Administration and order drug company Pfizer to issue "Dear Doctor" letters.
"(Pfizer) has also amended the Champix product information to include the same post-marketing information as in the US prescribing information," News.com.au quoted a TGA spokeswoman, as saying.
The new warning stated that "there have been reports of depressed mood, agitation, changes in behaviour, suicidal ideation and suicide in patients attempting to quit smoking while taking Champix".
"Because these events are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure."
Both the TGA and Pfizer have are unaware if Champix itself, nicotine deprivation or some other factor could lead to such the psychiatric reactions.
"The TGA will continue to monitor the situation," the spokeswoman said.
In the US Champix is marketed as Chantix, where it became popular in a highly-publicised case of a Texas musician who began taking the drug and then was shot dead after reportedly engaging in aggressive behaviour.
The mechanism of the drug involves stimulating the same receptors in the brain as nicotine, relieving the cravings and withdrawal symptoms of those giving up.
After the drug Zyban and nicotine replacement treatments like patches and gum, it will be the third pharmaceutical therapy available for smoking cessation.