Dose-dependent absorption of disodium etidronate.

The gastrointestinal absorption of disodium etidronate (as [14C]disodium etidronate) was investigated in the rat proximal jejunum in-situ. Studies using various initial concentrations of the drug suggested that etidronate absorption occurred by passive diffusion at initial concentrations below 0.08 M. At initial concentrations above 0.08 M, the rate of absorption was significantly greater than would be expected if passive diffusion was the only mechanism responsible for absorption. Etidronate absorption is not mediated by the carrier mechanism responsible for phosphate ion absorption.