Bioavailability of seven furosemide tablets in man

A seven-way crossover study was conducted in 14 healthy male volunteers to evaluate the relative bioavailability of seven different marketed 40 mg furosemide tablets. Each dose was administered as a single tablet after an overnight fast, and blood samples were obtained for 16 hours. Plasma was assayed by HPLC. There were no statistically significant differences among the seven products for the mean peak concentration (1.01-1.29 micrograms/ml), mean time of peak (1.2-2.1 h) or mean area under the plasma concentration-time curves, which differed by less than 14 per cent. However, one product exhibited greater intersubject variability, and on this basis was considered inequivalent to the other six products. Furosemide is a potent and widely used diuretic. Currently the United States Food and Drug Administration (USFDA) has granted approval to at least twelve manufacturers of 40 mg furosemide tablets, based in part on bioavailability data obtained in human subjects. In addition, the USFDA has granted an 'AB' therapeutic equivalence evaluation to each of these products, which is understood by many to indicate the therapeutic equivalence and interchangeability of these products. The objective of the present investigation was to directly compare the bioavailability of seven 40 mg furosemide tablet products which had previously been approved by the Food and Drug Administration.