The effects of cimetidine (Tagamet) on renal function in patients with renal failure

Cimetidine has been administered during 7 days to 28 patients with different degrees of renal failure. Thirteen of these patients had a further week's treatment at least one month later. The daily dose of cimetidine was reduced in relation to pretrial values of creatinine clearance. There was a clear rise in serum creatinine all through the trial (22.3 +/- 2.6% at day 7) (p < 0.001). Maximal decreases in creatinine clearance occurred on day 2 (21.8 +/- 2.2%) and day 3 (23 +/- 2.0%) (p < 0.001), but were still present on days 6 (16.4 +/- 2.9%) and 7 (17.3 +/- 2.8%) (p < 0.001). There was a small rise in serum uric acid all through the trial (p < 0.05). Three days after finished treatment there were no significant differences in serum creatinine, creatinine clearance and serum uric acid when compared to pretrial values. The pattern of changes in serum creatinine and creatinine clearance was the same in both mild and severe renal failure. Glomerular filtration rate determined by |52Cr¿ EDTA clearance before, on day 3 of treatment and 3 days after treatment did not show any differences. No change was seen in serum beta 2-microglobulin during the trial. The decrease in creatinine clearance during treatment with cimetidine is probably not caused by a reduction of glomerular filtration rate, but could be explained by competition by cimetidine for tubular secretion of creatinine. Treatment with cimetidine of patients with renal failure may invalidate measurements of serum creatinine and creatinine clearance as standard routine tests for glomerular filtration rate.