Teva Pharmaceutical Industries Ltd., the world’s largest generic-drug maker, pulled a copy of the antidepressant Wellbutrin XL from the U.S. market after regulators said it isn’t the same as the brand-name medicine.
The Food and Drug Administration conducted tests after patients complained that Teva’s 300-milligram copycat version of the extended release medicine didn’t work, Greg Geba, director of the agency’s Office of Generic Drugs, said. Eighty-five people reported concerns from January 2007 to June 2007 about the 300-mg dose of Teva’s Budeprion XL drug, which was approved in 2006.
While other generic medicines have been withdrawn because they don’t work as well as the brand, it hasn’t happened frequently, the FDA said. The agency said it may pursue other products. More than two years ago, regulators began discussing whether to tighten equivalency standards for copycat drugs.
“It spotlights the inaccuracy of the common myth that generics are identical to name brands,” Erik Gordon, a business professor at the University of Michigan in Ann Arbor who studies the drug industry. “They are supposed to be pharmacologically equivalent, not identical, and that leaves some wiggle room. Now we see that the FDA allows companies to guess that different doses are equivalent.”
Teva stock traded in Tel Aviv dropped as much as 1.9 percent to 157.5 shekels, the biggest intraday decline since Aug. 15, and was trading down 1.6 percent as of 10:37 a.m. The company’s American depositary receipts fell 1 percent to $40.79 at the close in New York yesterday.
GlaxoSmithKline Plc, based in London, sells Wellbutrin XL and splits profits with the manufacturer, Montreal-based Valeant Pharmaceuticals International Inc. Mylan Inc., based in Canonsburg, Pennsylvania, and Watson Pharmaceuticals Inc., based in Parsippany, New Jersey, also make generic versions.
The FDA initially required companies to study generic versions of Wellbutrin XL only in the 150-mg dose and allowed them to extrapolate the results to the 300-mg dose because of concerns with seizure risk, Barbara Davit, director of the division of bioequivalence II in the Office of Generic Drugs, said yesterday during a conference call. The agency will now require testing on the highest available strength, she said.
Impax Laboratories Inc., based in Hayward, California, makes the drug marketed by Petach Tikva, Israel-based Teva. Impax requested the FDA withdraw approval, and Impax and Teva have stopped shipping the product, Geba said.
“There is no material impact to Teva,” Denise Bradley, a spokeswoman for the company, said in an e-mail. “We have no comment on whether we will launch our own version of this product at this time.”
The withdrawal also isn’t material to Impax and the company won’t reveal whether it will attempt to bring another generic Wellbutrin XL to market, Mark Donohue, a company spokesman, said in a telephone interview. Impax fell 2.3 percent to $26.39 yesterday at the close of trading in New York.
About 2 percent of patients who take a generic version of the depression drug use Teva’s product, said Geba of the FDA.
The FDA’s Janet Woodcock, director of the Center for Drug Evaluation and Research, said in October 2010 that the agency was discussing tightening standards for how closely generic drugs resemble brand-name equivalents after patients and employees of generic-drug makers complained that some of the medicines don’t work as well as the brand-name counterparts.
The standards assure that the generic is absorbed at the same rate and extent as the brand-name version. At the time, Woodcock cited generic anti-seizure medications for concern.
In April 2010, a group of outside FDA advisers voted 11-2 that the agency’s equivalence requirements aren’t sufficient for certain medicines. An FDA official suggested then those medicines include digoxin for various heart conditions, lithium used to treat manic episodes, phenytoin for a certain type of seizures and the blood-thinner warfarin.
After the initial complaints in 2007 about Teva’s version of Wellbutrin XL, the agency determined recurring symptoms are common during major depressive disorder and the differences in the drugs weren’t outside established rules for equivalence.
The FDA asked Teva and Impax to study the 300-mg dose after the complaints. The agency decided to begin its own study in 2010 after the companies had problems enrolling patients, Geba said. The FDA produced results in August of its study in 24 patients comparing Teva’s copy with the brand-name.
The agency is revising new guidelines for bupropion, the active ingredient in Wellbutrin XL, and is asking makers of other copies of the medicine to retest their products, Geba said.