Smoking cessation drug Champix (varenicline) will carry new warnings of links with suicidal thoughts when it becomes available on the PBS next month.
Pfizer has amended the Champix product information to include the same post-marketing information as in the US prescribing information, following reports submitted to the US Food and Drug Administration (FDA) of depression, agitation and suicidal thoughts while taking the drug.
The new warning states 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".
The TGA said it was unknown whether Champix itself or some other factor triggered the reactions.
"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," a TGA spokeswoman said.
Doctors have been mailed letters informing them of the changes.