Actonel - Clinical Pharmacology

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Metabolism:

There is no evidence of systemic metabolism of risedronate.

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 over 28 days. Mean renal clearance is 105 mL/ min (CV = 34%) and mean total clearance is 122 mL/ min (CV = 19%), with the difference primarily reflecting nonrenal clearance or clearance due to adsorption to bone. The renal clearance is not concentration dependent, and there is a linear relationship between renal clearance and creatinine clearance. Unabsorbed drug is eliminated unchanged in feces. Once risedronate is absorbed, the serum concentration-time profile is multi-phasic, with an initial half-life of about 1.5 hours and a terminal exponential half-life of 480 hours. This terminal half-life is hypothesized to represent the dissociation of risedronate from the surface of bone.

Special Populations:

Pediatric:

Risedronate pharmacokinetics have not been studied in patients <18 years of age.

Gender:

Bioavailability and pharmacokinetics following oral administration are similar in men and women.

Geriatric:

Bioavailability and disposition are similar in elderly (> 60 years of age) and younger subjects. No dosage adjustment is necessary.

Race:

Pharmacokinetic differences due to race have not been studied.

Renal Insufficiency:

Risedronate is excreted unchanged primarily via the kidney. As compared to persons with normal renal function, the renal clearance of risedronate was decreased by about 70% in patients with creatinine clearance of approximately 30 mL/ min. ACTONEL is not recommended for use in patients with severe renal impairment (creatinine clearance <30 mL/ min) because of lack of clinical experience. No dosage adjustment is necessary in patients with a creatinine clearance

Hepatic Insufficiency:

No studies have been performed to assess risedronate's safety or efficacy in patients with hepatic impairment. Risedronate is not metabolized in rat, dog, and human liver preparations. Insignificant amounts (< 0.1% of intravenous dose) of drug are excreted in the bile in rats. Therefore, dosage adjustment is unlikely to be needed in patients with hepatic impairment.