Champix is often prescribed to help people quit smoking as it relieves the cravings and withdrawal symptoms, but the TGA says it has received 254 adverse drug reaction reports for Champix, involving a variety of side effects which include nausea, aggression and insomnia - more worrying is that some patients without any known psychiatric conditions have experienced suicidal thoughts after taking the drug.
The TGA says the drug is still available but doctors must warn patients of the possible side effects and tell them to seek immediate medical help if they experience such symptoms.
While the drug has not been banned, the TGA says there is an increasingly clear association between varenicline and mental problems and doctors, families and carers need to be vigilant for any changes in behaviour in the smoker.
The TGA says 210,000 prescriptions had been filled since January, when the drug first came onto the Pharmaceutical Benefits Schedule and by October 2008 they had received 339 adverse reaction reports with varenicline, 255 (72%) of which describe psychiatric symptoms including depression, aggression, agitation, abnormal dreams, insomnia, hallucination and anger; there have also been reports of suicidal/self-injurious ideation or behaviour.
The TGA also received 15 reports of seizures in patients using varenicline and say while it is not known how many of these had a prior history or risk of a seizure disorder, there is no experience from clinical trials of varenicline in patients with epilepsy.
Therefore the TGA says doctors are also advised to exercise caution when prescribing varenicline to patients with a history of seizure disorder.
There has been concern both in the U.S. and Britain regarding varenicline before the drug arrived in Australia as it had been linked to depression and suicides and in the U.S. the Food and Drug Administration (FDA) has also issued a similar warning about the drug's use.
Champix which is made by Pfizer, won the prestigious Prix Galien medal in 2008 and a statement from the company insists a causal link between the drug and the reported symptoms "has neither been established nor excluded".
Pfizer says Champix is an important treatment option for smokers who want to quit and say they stand by the efficacy and safety profile of the drug when used as directed.
While Pfizer says quitting smoking is associated with nicotine withdrawal symptoms and the exacerbation of underlying psychiatric illness, the TGA points out that suicidal behaviour had been reported in patients taking varenicline who had no known pre-existing psychiatric conditions.
The TGA says despite the link to nicotine withdrawal, it appears increasingly likely that there is an association between varenicline and serious neuropsychiatric events and patients who develop these symptoms, including suicidal thoughts, while taking varenicline should seek urgent medical help and stop taking varenicline.