New research in the United States on the anti-smoking drug Champix (Chantix-varenicline) says there have been 3,000 reports of side effects since the drug was approved for use there in 2006.
Champix has been available on the Pharmaceutical Benefits Scheme in Australia since January this year; it is a non-nicotine drug designed to help people to quit smoking.
The results of the research from the Institute for Safe Medication Practices, and Wake Forest University, have meant that doctors are now being warned to closely monitor their patients who are taking the anti-smoking drug.
In a pilot program aimed at identifying new drug risks in adverse drug events reported to the U.S. Food and Drug Administration (FDA), multiple safety problems associated with Champix have been revealed.
The drug has been linked to a wide range of injuries, including serious accidents and falls, potentially lethal cardiac rhythm disturbances, severe skin reactions, acute myocardial infarction, seizures, diabetes, psychosis, aggression and suicide.
Varenicline was approved by the FDA in May 2006, it works by blocking one of the nicotinic acetylcholine receptors in the brain and nervous system, while also providing a nicotine-like effect to help curb withdrawal; it is currently the only marketed and approved drug which acts in this manner.
In the last three months of 2007, varenicline was linked to 988 serious injuries in the U.S. reported to the FDA.
This is far more than any other individual drug in this time period and prompted the FDA to conduct an analysis of all adverse events for varenicline since marketing approval in 2006.
The FDA has recently issued a Public Health Advisory about one of the most marked adverse effects of varenicline, psychiatric symptoms that included "changes in behaviour, agitation, suicidal ideation, attempted and completed suicide".
It appears that from May 2006 to December 2007, the FDA received 227 domestic reports of suicidal acts, thoughts or behaviours, 397 cases of possible psychosis and 525 reports of hostility or aggression - amongst these were 28 cases of suicide and 41 mentions of homicidal ideation, 60 cases of paranoia and 55 cases of hallucination.
However, the drug is also linked to other kinds of serious harm for which no warnings currently exist, either from the FDA or from the manufacturer, Pfizer.
These include 173 serious events involving accidents and injuries, including 28 road traffic accidents and 77 falls, some leading to fractures of rib, facial bones, hand, ankle, spine, and lower limbs, where a variety of potential causes were identified, including loss of consciousness, mental confusion, dizziness and muscle spasms.
There were 148 reports of vision disturbances, including 68 cases described as blurred vision and 26 terms indicating transient or other forms of blindness.
There were 224 reports of heart rhythm disturbances including a sudden loss of consciousness, and 372 reports of a wide variety of movement disorders, including tremors, muscle spasms, twitching, tics, drooling and motor hyperactivity.
There were also 338 cases of hives or swelling of the tongue, face, eyes, lips or other areas and 65 cases were classified as severe and included blisters, exfoliation of the skin and lips, and Stevens-Johnson Syndrome.
The FDA also received 544 reports suggesting varenicline may be related to a loss of glycemic control, including many cases of weight loss or gain that could have alternative causes, but also identified numerous cases of symptoms and laboratory tests consistent with new onset diabetes.
The FDA now says there are safety concerns about the use of varenicline among persons operating aircraft, trains, buses and other vehicles, or in other settings where a lapse in alertness or motor control could lead to massive, serious injury.
The FDA recommends that patients and doctors exercise caution in the use of varenicline and consider the use of alternative approaches to smoking cessation.
The researchers say that while the data does not definitively prove that Champix is the culprit in all the cases, it does give a strong signal.