A comparison of the effect of frusemide and bumetanide on the diuretic response and fibrinolytic mechanism in man.

A double-blind, crossover trial has compared the diuretic response of ten normal male subjects to the oral administration of frusemide (40 mg) and bumetanide (1 mg). Both drugs gave a similar profile, with acute onset and cessation of response, and a marked peak effect. There was no significant difference between the times taken for each drug to produce its peak diuretic effect. The peak rate of diuretic response, and the total response for six hours after drug ingestion, were significantly greater after bumetanide, with respect to urinary volume and sodium excretion. The peak rate of magnesium excretion was greater after bumetanide. There was no difference between the drugs with respect to potassium, calcium or creatinine excretion or the urinary Na/K ratio. Following peak diuresis, potassium excretion did not show a linear return to its control value. At the time of peak diuresis, both drugs caused a significant reduction of euglobulin lysis time; levels of available plasmin were significantly lowered after frusemide, and levels of active plasmin were significantly raised after bumetanide. The significance of these findings in relation to the fibrinolytic mechanism is discussed. Estimations of plasma viscosity, serum total protein and magnesium concentrations showed that maximal haemoconcentration occurred several hours after diuresis.