Effects of renal failure on blood levels of cimetidine.

Serial blood samples for determination of drug levels were obtained after intravenous administration of 300 mg of cimetidine. Sixteen patients with varying degrees of renal failure were studied. There was a prolongation of drug half-life in patients with renal insufficiency compared with that in normal controls (P less than 0.001). A significant inverse relationship between the half-life and the creatinine clearance was noted (r= 0.69; P less than 0.01). The effect of hemodialysis was studied in 12 patients. Cimetidine was found to be dialyzable. This was demonstrated both by a shortening of the half-life of the drug during dialysis and by measurement of dialysance. This suggests that the dose schedule should be modified for patients with renal insufficiency and for those on hemodialysis. A single intraveno us dose of cimetidine was well tolerated by the patients. One patient developed an urticarial skin rash, believed to be allergic in nature. There was a transient, mild (but significant) rise in blood urea nitrogen and serum creatinine concentration in 5 patients with moderate renal failure.