A cheaper, generic version of GlaxoSmithKline Plc's Wellbutrin XL antidepressant is just as safe and effective, despite complaints from some patients, the U.S. Food and Drug Administration said on Wednesday.
The FDA said it received 85 reports from patients who switched from Wellbutrin XL to Teva Pharmaceutical Industries Ltd and Impax Laboratories Inc's cheaper generic, including 78 who said they slipped back into depression.
Other patients reported new or worsening side effects, including headaches, fatigue, anxiety and digestion issues.
"The question is whether the reported lack of efficacy and/or new onset side effects in these patients who switched suggest a problem with the generic product ... or have some other explanation," the FDA said in a statement on its website.
Agency scientists said they reviewed 300-milligram versions of the two drugs, which both use once-a-day formulations of the chemical bupropion, and found the data did not show that the problems stemmed from any differences between the two drugs.
“For the FDA to say that it has reviewed the safety and efficacy of this product is not correct,” stated Dr. Tod Cooperman, president of ConsumerLab.com, a Westchester, N.Y.-based provider of independent evaluations of health and nutrition products.
“No safety or efficacy testing of this novel 300 milligram formulation appears to have been conducted nor reviewed by the FDA. In fact, the FDA does not have bioequivalence data for this product.”
Last fall, test findings by that were released to MSNBC.com showed that the Teva's generic version of Wellbutrin XL 300 mg, sold as Budeprion XL 300 mg, didn't perform the same as the brand-name pill in the lab.
While both drugs contained the stated amount of bupropion, "dissolution testing" showed that the generic drug, which has a different time-release mechanism, released the active ingredient into a solution at a much quicker rate, which could impact its effect on a patient.
FDA officials received the reports during the first half of 2007. Teva and Impax's version of Wellbutrin was approved in 2006.
One factor that could account for the reported problems is the natural recurrence of depression, which can happen despite treatment, the FDA said.
Half of the patients who went back on the name-brand drug said they improved, the agency said, adding that it would continue to monitor the issue.
Watson Pharmaceuticals Inc also makes a 300-mg XL version of bupropion, though it was not part of the FDA's review.
GlaxoSmithKline makes other versions of Wellbutrin that face generic competition. Total sales of Wellbutrin slipped 37 percent last year in the face of generic competition, the company has reported.
The drugmaker could not comment on the FDA's conclusion because it did not have access to the data used but is pleased the agency would continue its monitoring, GlaxoSmithKline spokeswoman Mary Anne Rhyne said.
Teva spokeswoman Denise Bradley said the company would issue a statement later.
Reuters contributed to this report.