The regulation of generic drugs is based mainly on their bioequivalence (degree of similarity) to the original brand-name agents.
But the company has not conducted the kind of human tests, called bioequivalence studies, required for F.D.A. approval of generic drugs, he said.
Some branded companies appear to be exploiting the safety rules by denying research samples to would-be generic competitors, who are blocked at the Food and Drug Administration's entry gate because they cannot conduct bioequivalence studies.
Generally, the only test that a maker of a generic medication must perform to receive F.D.A. approval is one that establishes the "bioequivalence" of the product.
So for a few months you might receive a drug that was on the low side in the bioequivalence test, and then be switched to one on the high side of the test.
Even the amount of active ingredient -- what scientists call "bioequivalence" -- can vary considerably between different generic copies of the same drug, let alone between a generic and a different drug in the same class.
"We believe the study and the resulting data will provide further scientific support for the product's bioequivalence to the innovator drug," she said.
All the drug maker needs to demonstrate is that the generic version contains the same active ingredients, purity and quality, and provides "bioequivalence" -- meaning it produces the same level of drug in the blood over time as the brand-name version.
Instead of running costly clinical trials to prove their drugs' effectiveness, generic companies would now only have to prove "bioequivalence," that is, that their drugs contained the same key ingredients as the brand, and worked the same way.
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.
Some specialists, though, worry that the allowable range for bioequivalence is too wide, especially for patients who are taking medication to control problems like arrhythmias or seizures.
