1. Home>
2. Specialties>
3. General Medicine>
4. Summary and Comment

SUPPRESSED STUDY RELEASED: BRAND AND GENERIC LEVOTHYROXINE FOUND BIOEQUIVALENT.

Are generic and brand drugs bioequivalent? This single-blind, four-way, cross-over trial set out to answer that question, and spurred controversy about withholding research results in the process.

Researchers randomized 22 women with hypothyroidism to receive each of four (two brand and two generic) preparations of levothyroxine for six-week periods. No difference was found in peak serum concentrations and other measures of bioequivalence. There was no evidence of increased side effects with any of the four agents. This study was heavily publicized in the lay press because its sponsors -- the manufacturers of the leading brand preparation of levothyroxine (Synthroid) -- blocked its publication for at least two years and threatened legal action.

A second study showed that withholding research results is surprisingly common. Researchers mailed surveys to 3,394 life science faculty members at 50 universities with NIH funding. Of 2,167 respondents, 20 percent reported that publication of results had been delayed more than six months at least once in the last three years for reasons related to corporate interests (e.g., to allow patent application, protect a scientific lead, or slow dissemination of undesired results). Nine percent of respondents reported refusing to share research results with other university scientists.

Comment: The thyroid study, which demonstrated the bioequivalence of four levothyroxine preparations, will probably be remembered more for what it revealed about the ugly side of corporate funding than for its actual results. The authors point out that substituting less expensive versions for the leading brand preparation of levothyroxine could save as much as $356 million per year.

— TH Lee

Published in Journal Watch General Medicine April 25, 1997

Citation(s):

Dong BJ et al. Bioequivalence of generic and brand-name levothyroxine products in the treatment of hypothyroidism. JAMA 1997 Apr 16 277 1205-1213.

• Medline abstract (Free)

Blumenthal D et al. Withholding research results in academic life science: Evidence from a national survey of faculty. JAMA 1997 Apr 16 277 1224-1228.

• Medline abstract (Free)