Pharmacokinetics of Cytembena in chronic renal impairment

Renal excretion of Cytembena in subjects with a normal renal function amounted on the average to 7.8% of the given dose during 15 hours following a single intravenous administration of 200 mg of this cytostatic drug. In patients with an impaired renal function there was a further decrease in the urinary Cytembena excretion and this in direct relation to the decrease in endogenous creatinine clearance rate. The decline in renal Cytembena clearance is slower than that of glomerular filtration rate due, probably, to a lowered tubular reabsorption of Cytembena in residual nephrons. This change in tubular resorption of Cytembena is related to a decrease of the fractional reabsorption of sodium in residual nephrons. Serum Cytembena concentrations proved to be significantly lower in patients with impaired renal functions than in subjects with normal renal functions. This peculiarity of the pharmacokinetics of Cytembena is discussed from the aspect of a possible increase of its distribution volume in consequence of an increased concentration of the diffusible component.