Comparative bio-availability of four formulations of furosemide

Twelve healthy white male volunteers participated in a randomized double-blind cross-over study to compare the bio-availability of four brands of furosemide marketed in the RSA. A 40 mg tablet of each of the following formulations, purchased at random, was administered: Aquasin; Furetic; Lasix; and Puresis. Blood specimens were taken up to 5 hours and urine specimens collected up to 6 hours after medication. The following parameters were used to compare the formulations: (i) area under the plasma concentration time curve (AUC); (ii) maximal plasma concentration of furosemide (Cmax); (iii) time to maximal furosemide plasma concentration; (iv) cumulative urine volumes; and (v) cumulative excretion of furosemide in urine. Lasix was significantly superior to the other three products in respect of AUC and Cmax. With regard to cumulative urine volumes Lasix was significantly (P less than 0,05) superior to Aquasin in the first 3 hours after medication, significantly superior (P less than 0,05) to Puresis and comparable to Furetic over the entire 6-hour collection period. Lasix resulted in a significantly greater cumulative urinary excretion of furosemide than Puresis and Aquasin over the entire collection period. Lasix was superior to Furetic at 6 hours after medication. It is concluded that the bio-availability of Lasix is superior to that of the other products tested.