Let me start by saying I'm a fan of generic drugs. They save Americans billions of dollars each year and give us access to wonderful drugs at affordable prices. I've recommended generics in this column many times and use them myself when possible.
But there is a gnawing concern among some doctors and researchers that certain prescription generic drugs may not work as well as their brand-name counterparts. The problem is not pervasive, but it's something consumers should be aware of — especially now that more insurers insist that patients take generic medications when they are available.
Let me also prepare the groundwork for what I hope will be full and frank reader comments, by acknowledging that this issue is controversial.
Joe Graedon, who has been writing about pharmaceuticals for three decades and runs a consumer advocacy Web site, the People's Pharmacy (peoplespharmacy.com), was 100 percent behind generics for many years.
"We were the country's leading generic enthusiasts," he told me recently. But over the last eight or nine years, Mr. Graedon began hearing about "misadventures" from people who read his syndicated newspaper column, also called The People's Pharmacy.
The stories were typically from patients who were switched from a brand name drug to a generic one and had side effects or found that their symptoms returned — or even became worse than before they were medicated. Most recently Mr. Graedon has been hearing complaints on his Web site about generic forms of the antidepressant Wellbutrin XL 300 (known as Budeprion XL 300 in one generic form), the heart medicine Toprol XL (metoprolol succinate) and the antiseizure medicine Keppra (levetiracetam).
"Consumers are told generics are identical to brand name drugs, but that is clearly not always the case," Mr. Graedon said.
Some specialists, particularly cardiologists and neurologists, are concerned about generic formulations of drugs in which a slight variation could have a serious effect on a patient's health. The American Academy of Neurology has a position paper that says, in part, "The A.A.N. opposes generic substitution of anticonvulsant drugs for the treatment of epilepsy without the attending physician's approval."
But insurers tend to argue otherwise. On Thursday, ExpressScripts, which handles drug insurance for big employers, put out a news release announcing results of a study it sponsored that found no difference in hospitalizations or emergency-room visits for people on brand-name epilepsy drugs compared with those taking generics.
The Food and Drug Administration, meanwhile, says it stands behind generic medications and its methods for approving them.
"We have not seen any scientific studies that show generics do not hold up as well as brand name drugs," says Gary J. Buehler, director of the agency's office of generic drugs. "We believe the generic drugs we approve work in everyone."
The American Medical Association concurs. A spokeswoman for the group told me in an e-mail message, "the A.M.A. position is that as a whole generic drugs do work as well as name-brand drugs."
Yet, after hundreds of consumers posted messages about problems with the generic drug Budeprion XL 300 on the People's Pharmacy Web site, Mr. Graedon worked with an independent laboratory, ConsumerLab.com, to test the drug, which in other generic versions is typically known as bupropion.
The lab found that Budeprion XL 300 released the active drug at a different rate than the brand name Wellbutrin XL 300. Mr. Graedon and the lab conjecture that the different dissolution rates might be to blame for the reported side effects and lower effectiveness of Budeprion.
But Mr. Buehler at the F.D.A. explained to me that over the course of 24 hours a patient ends up with the same amount of the drug in the bloodstream, so there should be no reason for a variation in effectiveness. "We remain puzzled," he said.
The maker of Budeprion XL 300, Teva Pharmaceutical Industries, recently announced that it would conduct a clinical trial comparing its product against the original, Wellbutrin XL.
A Teva spokeswoman said in an e-mail message that the company was working with the F.D.A. on a study "specifically designed to answer the questions raised following the recent anecdotal commentary on generic budeprion."
"We believe the study and the resulting data will provide further scientific support for the product's bioequivalence to the innovator drug," she said.
To parse that statement — or at least understand "bioequivalence" — it is worth taking a step back to consider what a generic drug is and how it gets approved.