But the same streamlined process that makes generic drugs so cheap can open the door to problems like those seen with Teva's antidepressant. Developing and testing an original prescription drug can take more than a decade and cost upwards of $1 billion dollars, according to the Pharmaceutical Research and Manufacturers Association. The high price tag on most new drugs reflects the cost of years of trials that often involve hundreds of patients.
By comparison, generics are much less expensive because manufacturers are not required to repeat those costly studies. Instead the FDA asks companies to show that the drug is the same dose, strength and functions similarly in the body. In most cases, that means conducting a small study of 25 to 35 people showing that the generic drug is absorbed into the bloodstream at the same rate as the original drug. Usually regulators require a test of one dose of the drug, and then apply those results to other dosages.
FDA officials said Wednesday that this practice led to the mistaken approval of Teva's antidepressant. The FDA approved the drug based on a study of the 150 milligram dose of the drug, assuming the 300 milligram version of the drug would function similarly. An agency follow-up study showed that only 75 percent of the 300 milligram dose was actually being absorbed into the bloodstream.
"Based on the information we had available at that time we concluded that the 150 milligram strength was doing what it should, and that it was acceptable to extrapolate those findings to the 300 milligram strength" said Barbara Davit, director of bioequivalence for FDA's office of generic drugs.
Davit said the agency traditionally tests the lower dose of antidepressant drugs to avoid unnecessarily exposing patients to high doses. Davit said that approach "is no longer appropriate," and that the agency will test the highest dose when approving future versions of the drug.
In fact, while the FDA continues to tout the quality of generic drugs to the public, the agency has taken a more critical tone in discussions with industry. Earlier this year, the FDA's commissioner urged industry executives to put more focus on quality.
More than 225 drugs are currently in short supply, according to the American Society of Health-System Pharmacists, and many are cheap, generic drugs like sedatives, antibiotics and painkillers. Some of the shortages have been caused by manufacturing shutdowns due to plant contamination and other serious problems.
"Generic manufacturers need to be doing even more to ensure the quality of their products_for example, sharing best practices," Dr. Margaret Hamburg told members of the Generic Pharmaceutical Association. "And you have a particular responsibility to step forward when a product you are producing is medically necessary."
Despite the tough love from FDA officials, the agency continues to dedicate resources to bolster the image of generic drugs. Recent legislation passed by Congress includes FDA funding to study how differences in the color, shape and size of generic drug tablets can influence patients' view of their quality, compared to traditional products.
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