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Generic BP medication may be linked to higher adverse event rates
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Generic angiotensin II receptor blockers may be associated with increased risk for adverse events compared with brand-name counterparts, according to data published in Circulation: Cardiovascular Quality and Outcomes.
After generic commercialization of three antihypertensive drugs, higher adverse event rates were observed in generic users vs. brand-name users, according to the study.
“For generic users, we observed differences in rates of adverse events after generics commercialization using time series analysis,” Paul Poirier, MD, PhD, professor of the faculty of pharmacy at Laval University in Quebec, and colleagues wrote. “To our knowledge, this is the first ecological study assessing clinical outcomes with time series analysis after generics commercialization using a specific variable distinguishing between generic and brand-name users.”
The researchers used the Quebec Integrated Chronic Disease Surveillance System to observe the adverse event rates of losartan, valsartan and candesartan on 136,177 patients aged at least 66 years at 24 months prior and 12 months after generic commercialization.
Using negative binomial-segmented regression models, Poirier and colleagues compared periods before and after generic commercialization.
Among all angiotensin II receptor blocker users, there was a monthly mean rate of 100 adverse events for 1,000 users before and after generic commercialization.
Increase in adverse events
On the month of generic commercialization, there was an increase of adverse event rates of 8% among users of losartan (difference of proportions vs. brand names, 7.5%; 95% CI, –0.9 to 15.9), of 11.7% among valsartan users (difference of proportions, 17.1%; 95% CI, 9.9-24.3) and of 14% candesartan users (difference of proportions, 16.6%; CI, 7.9-25.3).
According to the study results, less than a year after generics commercialization, the monthly trend of adverse events was only affected among those treated with losartan (difference of proportions, 2%; 95% CI, 0.7-3.4).
Incremental risks
“More likely than not, the incremental risks observed by Poirier and colleagues were not entirely attributable to the use of generic drug preparations,” David Alter, MD, PhD, from the department of medicine at the University of Toronto, wrote in an accompanying editorial.
The use of segmentation analyses may not be the best approach because “systematic differences may have existed that explained why some patients received their generic drugs earlier than others,” Alter wrote.
“Poirier et al are ... correct in advising caution when interpreting their findings. They advocate instead, for further research,” he wrote. “However, what sort of future research also remains unclear. The methodological techniques the authors themselves employed and promoted underscores uncertainty about the optimal research methods that may be most appropriate when conducting drug surveillance research.”
Poirier told Cardiology Today that the findings underwent a rigorous review process.
“There are some limitations for the study, but ... at the end of the day, we ended up with the same conclusions,” Poirier said. “We're glad that the reviewer was so hard on us because it made us more confident in the data and I hope someone will run the same analysis with the same design in the United States. It could be a huge dataset to show if there is something there or not, and if it is there, then the next step will try to identify the patients who should not be changed to a generic.” – by Dave Quaile
For more information:
Paul Poirier, MD, PhD, can be reached at paul.poirier@criucpq.ulaval.ca.
Disclosures: Alter reports he has received funding from the Cardiovascular and Metabolic Rehabilitation, University Health Network-Toronto Rehabilitation Institute, University of Toronto. Poirier reports he has received honoraria from Abbott Vascular, Amgen, AstraZeneca, Boehringer Ingelheim, Bristol-Myers Squibb, Eli Lilly, Janssen, Merck, Novartis, Novo Nordisk, Pfizer, Roche, Sanofi Aventis, Servier and Valeant. Please see the study for all other authors’ relevant financial disclosures.
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