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by Salynn Boyles, Contributing Writer, MedPage Today
Cardiovascular event risk may increase in smokers who start using the cessation-assist drug varenicline (Chantix), according to findings from an observational study.
The retrospective analysis of medical records for close to 57,000 new users of varenicline living in Ontario, Canada, showed a statistically significant 34% increased risk for an emergency department visit or hospitalization for a cardiovascular event while taking the drug, compared to an observational period prior to starting varenicline.
In a subset of varenicline users who had not previously experienced a cardiovascular event, the increase in CVD event incidence while taking the drug, compared to the year prior to taking it, was 12%, the researchers wrote in a society-affiliated journal.
The researchers concluded that the "true cardiovascular risk of varenicline likely lies between these two estimates."
"We also observed a small 6% increase in the incidence of neuropsychiatric hospitalizations and emergency department visits that was not robust to sensitivity analyses," researcher Andrea Gershon of Toronto's Institute for Clinical Evaluative Sciences, and colleagues, wrote.
"Previous studies regarding the safety of varenicline have been conflicting and most examined people with relatively similar characteristics and backgrounds in highly controlled settings. We wanted to study varenicline among all kinds of people in the real world," Gershon noted in a press statement.
The researchers conducted a population-based, self-controlled risk interval study using linked universal health administrative data from the diverse, multicultural population of Ontario, Canada.
In two separate analyses, new varenicline users from Sept. 1, 2011, to Feb. 15, 2014 were followed from one year before to one year after starting varenicline. Adverse events, including hospital admissions and emergency room visits for cardiovascular and neuropsychiatric episodes, were counted during the year prior to starting the drug and the 12 weeks immediately afterward, the usual length of a varenicline prescription.
Cardiovascular events included heart attack, stroke, arrhythmias, unstable angina, peripheral vascular disease, and related conditions.
Among 56,851 new users of varenicline, 4,185 had one or more cardiovascular or neuropsychiatric hospitalizations and 4,720 had emergency department visits for these causes during the observation period.
Among the main study findings:
- Relative incidence 1.34 for cardiovascular events (95% CI 1.25 to 1.44)
- Relative incidence 1.06 for neuropsychiatric events (95% CI 1.00 to 1.13)
- Sensitivity analyses confirmed the increase for cardiovascular events but not consistently for increased neuropsychiatric risk.
"We estimate that 3.95 cardiovascular adverse events (95% CI 3.12 to 4.76) per 1,000 varenicline users were attributable to varenicline during the 12 week risk interval," the researchers wrote.
They noted that in addition to the observational nature of the study, which precludes assigning cause and effect, other study limitations included the lack of data on whether varenicline was taken as prescribed and the lack of information on individual smoking habits.
"Success in quitting smoking could have theoretically led to a lower cardiovascular event rate in the post-exposure control interval, making the event rate in the risk interval appear relatively high. However, given low cessation rates -- even with smoking cessation therapy -- and their impact, this would not likely have accounted for results observed."
Awareness of FDA warnings of neuropsychiatric adverse events during the time of the study may have led physicians and patients to increase monitoring for these complications, "thus preventing them from progressing."
"This might mean our findings are generalizable to people who receive such monitoring and the (neuropsychiatric) risk of varenicline is greater in those who do not," the researchers wrote.
Funding for the study by Gershon et al was provided by the Government of Ontario, Canada and the Institute for Clinical Evaluative Sciences.
Source: Society journal
--From MedPage Today