Ranitidine has no influence on tubular creatinine secretion.

Oral cimetidine competitively inhibits tubular secretion of creatinine. We investigated the potential of oral ranitidine, a comparable H2-receptor antagonist, to block tubular creatinine secretion. In 10 healthy subjects, clearances of inulin and endogenous creatinine were simultaneously measured before and after administration of a single oral dose of ranitidine. In all subjects the effect of 300 mg ranitidine was studied; 7 subjects with high tubular secretion also participated in an additional study, when 1,200 mg ranitidine was administered. Neither dose of ranitidine caused a significant change in glomerular filtration rate measured by inulin clearance, or in mean plasma creatinine or in mean creatinine clearance. We conclude that a single oral dose of 300-1,200 mg ranitidine does not inhibit tubular secretion of creatinine in normal subjects, probably due to a lower affinity of ranitidine for the transport carrier at the luminal tubular membrane in comparison with cimetidine.