Age and renal clearance of cimetidine

Abstract

In 35 patients (ages 20-86 yr) receiving cimetidine therapeutically, 2 serum samples and all urine formed in the interim were collected for analysis of cimetidine by high-pressure liquid chromatography and for creatinine. Cimetidine clearance decreased with age. The extrapolated 6-h serum concentration of cimetidine/unit dose, after i.v. cimetidine, increased with age of the patients. The ratio of cimetidine clearance to creatinine clearance (Rc) averaged 4.8 .+-. 2.0, indicating net tubular secretion for cimetidine. Rc seemed to be independent of age and decreased with increasing serum concentration of cimetidine, suggesting that secretion of cimetidine is a saturable process. There was only 1 case of dementia possibly due to cimetidine (with a drug level of 1.9 .mu.g/ml 6 h after a dose) in a group of 13 patients without liver or kidney disease who had cimetidine levels above 1.25 .mu.g/ml. High cimetidine levels alone do not always induce dementia.