Researchers have found public perception bias may lead to more frequent reporting of adverse events for generics
A US study has explored whether adverse event reporting patterns are similar between brand and generic drugs, using authorised generic (AG) drugs as a control for possible perception bias.
AG drugs contain the exact active and inactive ingredients as the branded drug, but are sold and distributed with a generic label.
The marketing of AG drugs began in the early 1990s as a strategy for brand name companies to maintain market share, but became a widespread practice about a decade later, the researchers point out.
The cardiovascular medications amlodipine (Norvasc), losartan (Cozaar), metoprolol extended release (metoprolol ER—Toprol XL) and simvastatin (Zocor) were used for the study, chosen for their common use and adequate historical reporting data.
Adverse events reported to the FDA Adverse Event Reporting System from 2004-2015 were analysed.
Reports were included when the above drugs were listed as the primary or secondary suspect drugs, but were excluded when they were listed as interacting or concomitant.
Drugs were classified as brand, AG or generic based on drug and manufacturer names.
Researchers found significant differences in reporting odds ratios when comparing brand versus generic.
However there were fewer differences when comparing brand versus AG.
For example, the reporting odds ratio for generic amlodipine for liver injury was significantly higher than the corresponding ratio for the brand.
Yet no significant difference between brand and AG reporting odds ratio was found.
Another example was the generic losartan, which had a reporting odds ratio for acute renal failure that was significantly higher than the corresponding brand ratio.
“Our results showed no significant differences were found for many adverse events when comparing AGs and generics,” say the researchers.
“Assuming the AG represents the brand product in terms of safety and effectiveness but it perceived as a generic, this would suggest that the reporting differences between brand and generic are at least in part related to perception bias.
“Our results demonstrate that the public perception bias against generics is found in adverse event reporting.”
There are several limitations to the study, the researchers point out, including that analysis was limited to just four cardiovascular drugs with different safety profiles.
Misclassification of adverse events for generic drugs to branded drugs was a concern.
“It is likely that patients and providers are more aware of brand manufacturer name than the generic manufacturer, so they report to the brand name manufacturer out of familiarity,” the researchers posit.
Requiring the manufacturer name to be printed on the prescription bottle or packaging could improve the accuracy and reliability of using AGs for post-marketing surveillance, they say.
The research was published in the Journal of Clinical Pharmacy and Therapeutics.