A drug interaction study of ceftriaxone and frusemide in healthy volunteers.

Ceftriaxone, a recently developed cephalosporin significantly reduced the diuretic activity of frusemide in rats. For this reason and because an interaction of unknown mechanism is well established between frusemide and some cephalosporins, we studied the interference of ceftriaxone with the diuretic effect of frusemide in healthy volunteers. Twelve subjects received frusemide (40 mg p.o.) or placebo in combination with ceftriaxone (2 g i.v.) or saline on 4 different days (cross-over, randomized, single-blind study). Urine was collected in small portions during 24 hours after medication and analyzed for volume, osmolality, Na+, K+, Cl- and creatinine concentration. Ceftriaxone had neither an effect on basal urinary output and electrolyte excretion nor on the specific diuretic action of frusemide.