Elimination of oral cimetidine in chronic renal failure and during haemodialysis.

1 The absorption and elimination of a single oral dose of 400 mg cimetidine was studied in fourteen fasting patients with impaired renal function. In addition, the dialysance of cimetidine was studied in five patients on haemodialysis. 2 The absorption was somewhat, but clinically insignificantly delayed. A second unexplained peak in the absorption curve was found. 3 First order elimination kinetics were confirmed and the length of time of a cimetidine concentration over 0.5 mg/l could be correlated with creatinine clearance. 4 The magnitude of extra renal elimination was estimated to be approximately one fourth of total cimetidine elimination in normal patients and seemed unaffected by impaired renal function. 5 A dose schedule based on AUC found in the patients in renal failure is suggested. The recommendations for daily oral dose range from 300 mg (at borderline dialysis) to 1000 mg in mild renal failure. The suggested doses will give an average plasma concentration of the same order as seen in patients with normal renal function.