NEW YORK, April 15 (Reuters) -- The generic form of a common thyroid medication is just as effective as the more expensive name-brand drug that many doctors prescribe, according to California investigators.
Although concern has been raised in the past that generic drugs may not be as effective as their name-brand counterparts, the new study suggests that patients get the same benefit from the generic versions of the drug levothyroxine sodium -- and at a significant cost savings over the brand-name preparations.
An estimated $356 million in drug costs could be saved per year if the 8 million American users of thyroid medication switched to the generic brands, the researchers concluded. Most of these prescriptions are written for patients who suffer from hypothyroidism, the medical term for an underactive thyroid.
"Based on our findings, we believe that the four generic and brand-name preparations in this study are bioequivalent by current Food and Drug Administration (FDA) criteria for oral drugs and are interchangeable without loss of therapeutic efficacy in the majority of patients for treatment of hypothyroidism," wrote Dr. Betty J. Dong, of the University of California Medical Center in San Francisco.
Hypothyroidism leads to a sluggish metabolism and loss of energy. Patients with the deficiency typically must take life-long hormone replacement therapy in the form of levothyroxine. Name brands for levothyroxine include Synthroid and Levoxyl.
Over the course of the study, 22 women with hypothyroidism were given both forms of the brand-name levothyroxine and two forms of generic levothyroxine for identical periods of time.
When the researchers compared the women's thyroid function on each of the four forms of the thyroid drug, no significant differences were seen in terms of how the drugs performed, according to Dong.
Although all four drugs were not entirely identical -- some slight differences were seen -- the majority of people with hypothyroidism can probably safely take any of the four drugs, Dong wrote. However, doctors should be performing regular assessment of thyroid status and monitoring thyroid function regardless of the brand of levothyroxine being used, she added.
In an unusual twist, the journal in which the study was published is charging that one of the makers of name-brand thyroid medication tried to discredit the study and prevent it from being published for fear that sales of their drug would suffer.
According to Dr. Drummond Rennie, editor of The Journal of the American Medical Association, Flint Laboratories (subsequently bought by Boots Pharmaceuticals, the manufacturing arm of which is now owned by Knoll Pharmaceutical) originally financed the study nine years ago assuming that it would show its brand of thyroid medication (Synthroid) to be more effective than the others. When the results showed all four drugs (generic and name-brand) to be about equally effective, Boots Pharmaceuticals began charging that the study was flawed and used a variety of legal tactics to stall publication.
"It is our belief that this is a good study carried out by highly competent workers following a sensible design that tried to answer an important question," wrote Rennie. "It is hard to believe that the sponsors would have made such extraordinary efforts to delay and block publication of the study for such a very long time and for such an extraordinary number of specious reasons if the results had shown Synthroid to be better."
SOURCE: The Journal of the American Medical Association (1997;277:1205-1213, 1238-1243)
