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Sponsors lose fight to stop thyroxine study publication

1997; Volume: 349; Issue: 9059 Linguagem: Inglês

10.1016/s0140-6736(97)23016-3

0099-5355

Michael McCarthy,

Pharmacogenetics and Drug Metabolism

In 1990, when Betty J Dong, a researcher at the University of California medical Center, San Francisco, USA, reported the results of her study (panel) comparing the bioequivalence of several levothyroxine preparations to the study's sponsor, Boots Pharmaceuticals, company officials were not happy. Dong and her colleagues had found that two generic levothyroxine preparations and one lower-priced brandname product were bioequivalent to Synthroid, a more expensive drug and one of Boots' top-selling products. There seems to be little difference between two generic levothyroxine preparations, a low-priced brand-name preparation, and the higher-priced brandname product, Synthroid. So report researchers from the University of California Medical Center, San Francisco, USA, who publish their results this week. The study was actually completed 7 years ago, but its publication was suppressed by the study's sponsor, Knoll Pharmaceutical, makers of Synthroid. 22 hypothyroid women, who had been clinically and chemically euthyroid for at least 3 months, participated in a four-way crossover study comparing the bioavailability of brand-name products, Synthroid and Levoxin (now called Levoxyl) with two generic products (JAMA 1997; 277: 1205–13). At the start of the study, the women were taking 0·1–0·15 mg levothyroxine per day. All of them took each of the products for 6 weeks at the same doses as they were taking when they enrolled. The study was randomised and the primary investigators were blinded to the treatments. “No significant differences between the 4 products were found in area under the curve or peak serum concentrations of total thyroxine, total triiodothyronine, or free thyroxine index”, the researchers report. They conclude that the four preparations “are interchangeable without loss of therapeutic efficacy in the majority of patients for treatment of hypothyroidism”. There seems to be little difference between two generic levothyroxine preparations, a low-priced brand-name preparation, and the higher-priced brandname product, Synthroid. So report researchers from the University of California Medical Center, San Francisco, USA, who publish their results this week. The study was actually completed 7 years ago, but its publication was suppressed by the study's sponsor, Knoll Pharmaceutical, makers of Synthroid. 22 hypothyroid women, who had been clinically and chemically euthyroid for at least 3 months, participated in a four-way crossover study comparing the bioavailability of brand-name products, Synthroid and Levoxin (now called Levoxyl) with two generic products (JAMA 1997; 277: 1205–13). At the start of the study, the women were taking 0·1–0·15 mg levothyroxine per day. All of them took each of the products for 6 weeks at the same doses as they were taking when they enrolled. The study was randomised and the primary investigators were blinded to the treatments. “No significant differences between the 4 products were found in area under the curve or peak serum concentrations of total thyroxine, total triiodothyronine, or free thyroxine index”, the researchers report. They conclude that the four preparations “are interchangeable without loss of therapeutic efficacy in the majority of patients for treatment of hypothyroidism”.