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Canadian Pharmacy |
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Pharmacokinetics
Absorption
The absorption of an oral dose is relatively rapid and occurs throughout
the upper gastrointestinal tract. The fraction of the dose absorbed is independent
of dose over the range studied (single dose, 2.5 to 30 mg; multiple doses,
2.5 to 5 mg). Steady-state conditions in the serum are observed within 57
days of daily dosing. Mean absolute oral bioavailability of the 30-mg tablet
is 0.63% (90% CI: 0.54% to 0.75%) and is comparable to a solution. The extent
of absorption of a 30-mg dose (three 10-mg tablets) when administered 0.5
hours before breakfast is reduced by 55% compared to dosing in the fasting
state (no food or drink for 10 hours prior to or 4 hours after dosing).
Dosing 1 hour prior to breakfast reduces the extent of absorption by 30%
compared to dosing in the fasting state. The result of absorption is similar
either your dosing before 0.5 hours to breakfast or 2 hours after dinner
(evening meal). The effect of ACTONEL shows when it is taken at least 30
minutes before breakfast.
Metabolism
No confirmation has shown of systemic metabolism of risedronate.
Elimination
Around 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. Renal
clearance is 105 mL/min and means the total clearance is 122 mL/min, 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. |
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