Pharmacokinetic and pharmacodynamic analysis of the antihypercalcemic effect of incadronate disodium in rats

Incadronate concentrates into the bone as a target organ after intravenous administration of incadronate disodium. Mature osteoclasts has take up inca dronate from the bone surface and convert it from an active to an inactive form. As a result, incadronate decreases the plasma calcium concentration b y suppressing bone resorption. In this study, the pharmacokinetic and pharm acodynamic (PK/PD) analysis model for ascertaining the antihypercalcemic ef fects of incadronate disodium was developed in rats. Data on both the conce ntration of incadronate in bone and that of free calcium in blood after int ravenous administration from our previous study were used for analysis. To estimate the concentration in the surface laver of bone, data on the concen tration of incadronate in bone after single intravenous administration were analyzed based on the PK model considering three-compartments. The estimat ed concentrations in the surface layer in bone were applied to the PD model as an input function. The PD model was developed to analyze the changes in the plasma calcium concentration after a single intravenous administration considering an irreversible inhibition of osteoclast activity. The obtaine d fitted curves were in good agreement with the observed data. The model co uld explain the long duration of the antihypercalcemic effect of incadronat e disodium and should be useful for planning rational dose regimens for eff ective antihypercalcemic therapy.