Sodium bicarbonate Naproxen

Figure 10.3 Mean plasma concentrations ( [ g cm of naproxen in 14 male volunteers with and without intake of sodium bicarbonate, magnesium oxide or aluminium hydroxide.

Naproxen is absorbed fully when administered orally. Food delays the rate but not the extent of absorption. Peak concentrations in plasma occur within 2 to 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 half-life of naproxen in plasma is variable. It is about 14 hours in the young, but it may increase about twofold in the elderly because of age-related decline in renal function. 

With respect to concomitant antacid administration past studies have shown that sodium bicarbonate enhances the rate of naproxen absorption, magnesium carbonate caused a slight reduction, and a mixture of magnesium oxide and aluminium hydroxide gave a clear reduction in the rate of naproxen absorption (17). 

Sodium bicarbonate increased the rate of naproxen absorption, and aluminium hydroxide and magnesium oxide decreased it. Dimeticone did not affect ketoprofen bioavailability. 

Sodium bicarbonate 700 mg or 1.4 g increased the rate of absorption of a single 300-mg dose of naproxen in 14 healthy fasted subjects, whereas magnesium oxide or aluminium hydroxide 700 mg had the opposite effect, and reduced the rate of absorption. Magnesium carbonate had little effect. On the other hand when 15 or 60 mL of aluminium/magnesium hydroxide (Maalox) was given, the rate and extent of absorption of naproxen were slightly increased. ... 

Sodium bicarbonate and aluminium hydroxide appear to have a similar effect on naproxen, namely an increased and decreased effect, respectively, on the rate of absorption. However, note that these effects were seen in the fasted state, and may not apply when the NSAIDs are taken with or after food (as is recommended), as is the case with diflunisal , (p.I40). 

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