Generic antidepressant draws complaints.

FDA said Oct. 25 it is investigating complaints about a generic version of the antidepressant drug Wellbutrin XL after users reported having headaches, anxiety and other ailments, "The International Herald Tribune" reported.

FDA spokesperson Sandy Walsh told Dow Jones Newswires the agency is also reviewing the scientific formulation of the drug, called Budeprion XL, after a consumer product testing group published results that showed key differences from the original drug.

The tests, conducted by ConsumerLab.com, came after Budeprion XL users earlier this year began complaining that the drug caused severe headaches, digestive problems, anxiety, tremors, and insomnia. Another Web site, peoplespharmacy.com, reported that more than 250 people had complained about the drug.

Budeprion XL is made by U.S.-based Impax Laboratories and sold by Israeli firm Teva Pharmaceutical Industries.

FDA said it could not provide data to support ConsumerLab's findings. "FDA cannot offer any examples where generics have been shown to not perform as expected. FDA has many years of experience in the review of generic drugs and has great confidence in the quality and equivalence of generic drug products," the agency said.

In 2005, Canadian firm Biovial petitioned FDA to require rigorous testing on generic versions of Wellbutrin XL before being approved. While some saw it as a delay tactic, the company said it was to protect patients from serious risks, such as seizures.

FDA approved the first generic versions of Wellbutrin XL in 2006.