Study: Pfizer's Chantix, GlaxoSmithkline's Zyban not linked to increase in serious neuropsychiatric adverse events

Study results published in The Lancet suggest that the smoking cessation drugs Chantix (varenicline), marketed by Pfizer, and Zyban (bupropion), sold by GlaxoSmithkline, are not associated with an increase in serious neuropsychiatric adverse events versus placebo and nicotine replacement therapy.

The EAGLES trial, which was conducted by Pfizer and GlaxoSmithKline, was undertaken at the request of the FDA and the European Medicines Agency to compare the risk of clinically significant neuropsychiatric events, including but not limited to suicidality, in 8144 adults using smoking cessation products. The study, which had a 12-week treatment period, also looked at whether individuals with a history of psychiatric disorders are at greater risk for developing clinically significant neuropsychiatric events compared to individuals without a history of psychiatric disorders while using Chantix or Zyban.

According to the study authors, the trial did not show a significant increase in the incidence of the composite primary safety endpoint of serious neuropsychiatric adverse events with Chantix or Zyban compared to placebo and nicotine patch. The trial's main safety endpoint was defined as the occurrence of at least one treatment-emergent severe adverse event of anxiety, depression, feeling abnormal, or hostility and/or the occurrence of at least one treatment-emergent moderate or severe adverse event of agitation, aggression, delusions, hallucinations, homicidal ideation, mania, panic, paranoia, psychosis, suicidal ideation, suicidal behaviour or completed suicide.

Specifically, results showed that the incidence of the primary safety endpoint in patients without a history of psychiatric disorders was 1.3 percent for Chantix, 2.2 percent for Zyban, 2.5 percent for nicotine patch and 2.4 percent for placebo. Meanwhile, the incidence rates in patients with a history of psychiatric disorders were 6.5 percent for Chantix, 6.7 percent for Zyban, 5.2 for nicotine patch and 4.9 percent for placebo.

In addition, Pfizer noted that the results showed that patients with and without a history of psychiatric disorders taking Chantix had significantly higher continuous abstinence rates than patients treated with Zyban or nicotine patch during both the last four weeks of the 12-week treatment period and a 12-week non-treatment follow-up period.

Last year, <a href="http://www.firstwordpharma.com/node/1312808?tsid=33">study results</a> published in The Lancet Respiratory Medicine suggested that both Chantix and Zyban were not associated with an increased risk of any cardiovascular or neuropsychiatric event compared with nicotine replacement treatment. In 2009, the FDA required Pfizer and GlaxoSmithKline to include a <a href="http://www.firstwordpharma.com/node/369011?tsid=33&tsid=17&tsid=17&tsid=... warning</a> on their Chantix and Zyban about the risk of "serious mental health events, including changes in behaviour, depressed mood, hostility, and suicidal thoughts."

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