Generic Equivalence Problems Come Up Again

In early May, Bloomberg news reported the FDA will be conducting studies into generic extended release Toprol XL after almost 3,500 adverse incident reports have amassed since March 2009.

The FDA did conduct initial tests that showed the Toprol XL generic forms, metoprolol succinate, dissolved properly. However, based on the adverse incident reports, which Bloomberg News said were related to lack of effectiveness and side effects, the FDA http://grants.nih.gov/grants/guide/rfa-files/RFA-FD-14-024.html is now going to conduct PK/PD studies to establish therapeutic equivalence.

There are some similarities between this FDA action and its findings into a generic version of Wellbutrin XL 300 mg about 18 months ago. In October 2012, the FDA released this information regarding a generic form of Wellbutrin XL 300 mg, Budeprion XL 300 mg for major depressive disorder, stating the generic was not therapeutically equivalent. In that case, FDA began receiving reports of adverse events or lack of an effect in patients taking Budeprion in January 2007. Budeprion, which was manufactured by Impax/Teva, was approved in December 2006. After receiving approximately 85 reports in a six-month period, which were specific to Impax/Teva and not other Wellbutrin XL generic manufacturers, the FDA asked the manufacturer to conduct its own studies. Those studies closed in late 2011 citing a lack of enrollment. FDA sponsored its own comparison study in healthy volunteers and received results in August 2012.

In that case, FDA had approved the Budeprion XL 300 mg dose based on extrapolated data based on budeprion XL 150 mg because of risk of seizures in the generic, they did not pursue data for the higher dose as a precaution to exposure. 

The generic forms of metoprolol succinate are manufactured by Wockhardt Ltd., Dr. Reddy’s Laboratories in India, and Mylan and Actavis in the United States.