Residron Mechanism of Action

Pharmacology: Mechanism of Action: Risedronate sodium is a pyridinyl bisphosphonate that binds to bone hydroxyapatite and inhibits osteoclast-mediated bone resorption. The bone turnover is reduced while the osteoblast activity and bone mineralization is preserved.
Pharmacokinetics: Absorption: Absorption after an oral dose is relatively rapid (tmax-1 hour) and is independent of dose over the range studied (single dose study, 2.5 to 30 mg: multiple dose studies, 2.5 to 5 mg daily and up to 50 mg dosed weekly). Mean oral bioavailability of the tablet is 0.63% and is decreased when risedronate sodium is administered with food. Bioavailability was similar in men and women.
Distribution: The mean steady state volume of distribution is 6.3 l/kg in humans.
Plasma protein binding is about 24%.
Metabolism: There is no evidence of systemic metabolism of risedronate sodium.
Elimination: Approximately half of the absorbed dose is excreted in urine within 24 hours, and 85% of an intravenous dose is recovered in the urine after 28 days. Mean renal clearance is 105 ml/min and mean total clearance is 122 ml/min, with the difference probably attributed to clearance due to adsorption to bone. The renal clearance is not concentration depended, and there is a linear relationship between renal clearance and creatinine clearance. Unabsorbed risedronate sodium is eliminated unchanged in faeces. After oral administration the concentration-time profile shows three elimination phases with a terminal half-life of 480 hours.