Naproxen, (aleve, naprosyn, others), is absorbed fully when administered orally. Food delays the rate but not the extent of absorption. Peak concentrations in plasma occur within 2-4 hours and are somewhat more rapid after the administration of naproxen sodium. Absorption is accelerated by the concurrent administration of sodium bicarbonate but delayed by magnesium oxide or aluminum hydroxide. Naproxen also is absorbed rectally, but more slowly than after oral administration. The t/2 of naproxen is -14 hours in the young; it may increase about twofold in the elderly because of age-related decline in renal function (Table 26-1).
Metabolites of naproxen are excreted almost entirely in the urine. About 30% of the drug undergoes 6-demethylation, and most of this metabolite, as well as naproxen itself, is excreted as the glucuronide or other conjugates.
Naproxen is almost completely (99%) bound to plasma proteins after normal therapeutic doses. Naproxen crosses the placenta and appears in the milk of lactating women at ~1% of the maternal plasma concentration.
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