Pfizer has suffered something of a jolt with the news that US regulators are looking into reports of suicidal thoughts and aggressive and erratic behaviour in patients who have taken the firm’s smoking cessation product Chantix.

As part of an ongoing safety review, the US Food and Drug Administration is evaluating post-marketing data submitted by Pfizer and says that “a preliminary assessment reveals that many of the cases reflect new-onset of depressed mood, suicidal ideation, and changes in emotion and behaviour within days to weeks of initiating Chantix (varenicline) treatment”. The agency also cites a “highly-publicised case of erratic behaviour leading to the death of a patient using Chantix to attempt to quit smoking’, in reference to the death of Carter Albrecht, a member of the US band New Bohemians.

Drowsiness also investigated
Mr Albrecht was shot in the head in September by his girlfriend’s neighbour as he tried to kick down the man’s door. However, an autopsy revealed that the musician’s blood alcohol level was three times the legal limit. Aside from that case, the FDA has asked Pfizer for additional cases that might be similar and is also evaluating reports of drowsiness in patients taking Chantix, sold elsewhere as Champix affecting their ability to drive or operate machinery.

The agency has urged healthcare professionals to monitor patients on the drug for changes in behaviour and mood, but is quick to note that “the role of Chantix in these cases is not clear because smoking cessation, with or without treatment, is associated with nicotine withdrawal symptoms and has also been associated with the exacerbation of underlying psychiatric illness”. However, not all patients described in these cases had the aforementioned psychiatric illness and not all had discontinued smoking.

Chantix has proved to be a successful drug for Pfizer since its launch in August last year and had sales of $241 million in the third quarter. The company issued a statement saying that there is no scientific evidence establishing a causal relationship between Chantix and these reported events. In clinical trials involving more than 5,000 patients, adverse events related to changes in behaviour or psychiatric symptoms, including suicidal ideation, were rare and occurred at a rate comparable to placebo-treated patients and in the studies there were no actual suicides.

Judge limits Celebrex lawsuits
The Chantix news took the shine off what had started as a good day for Pfizer after it had won a US court ruling that could significantly limit the number of lawsuits against the firm which claimed that its COX-2 inhibitor Celebrex (celecoxib), which is still on the market, caused heart attacks and strokes.

Judge Charles Breyer of US District Court for Northern California ruled that that lawyers for more than 3,000 plaintiffs in the case failed to produce "scientifically reliable evidence that Celebrex causes heart attacks or strokes when ingested at the 200mg a day dose," the most commonly prescribed dosage. In particular, he criticised two specialist witnesses for the plaintiffs.

Judge Breyer described a cardiologist, Neil Doherty, as a clinical physician “with no relevant research experience and who developed his opinion for the purpose of testifying, bases his opinion on a study that he fundamentally misunderstood, is counter to the great weight of the evidence, and, by his own admission, does not make biological sense”. Similarly, the opinion put forward from neurologist Maryilyn Rymer “is also not good science. She ignores all the evidence that contradicts her litigation-created conclusion and instead bases her opinion on the same cherry-picked study as Dr Doherty”, the judge said.

Pfizer General Counsel Allen Waxman said the decision “recognises the lack of any credible evidence linking Celebrex, at its most common dosage form, with heart attacks or strokes". He added that the ruling will “greatly limit the scope of this litigation”, noting that Pfizer intends to “continue to vigorously defend the cases against us." Those other cases involve a 400mg dose of Celebrex.