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January 8, 1988

Generic Drugs: Bioequivalence and Bioavailability

Author Affiliations

University of Michigan Medical Center Ann Arbor

University of Michigan Medical Center Ann Arbor

JAMA. 1988;259(2):220. doi:10.1001/jama.1988.03720020022028

To the Editor.  —In the SPECIAL COMMUNICATION by Nightingale and Morrison1 concerning generic drugs, the subject of bioequivalence was discussed. However, no mention was made of bioavailability.In the past year, I have personally seen six patients who complained about the lack of effectiveness of oral estrogen therapy in alleviating their symptoms. Specific questioning revealed a difference between the control of their menopausal symptoms with the use of generic as opposed to brand name conjugated estrogens.In each instance, estradiol levels were below 37 pmol/L (10 pg/mL) or nondetectable. When these patients were switched to brand name conjugated estrogens, their menopausal symptoms were alleviated and their estradiol levels when rechecked were all above 165 pmol/L (45 pg/mL).The equine estrogens or synthetic estrogens are required by the United States Pharmacopeia to contain 50% to 63% estrone sodium sulfate, 22.5% to 32.5% equilin sodium sulfate, not more than 20% dihydroequilin,