Sex differences in plasma half-life of dextrorphan in rats administered dextromethorphan.

Male and female rats exhibited striking differences in their ability to metabolize dextromethorphan. Upon oral administration of this drug, the plasma half-life of dextrorphan, a major biotransformation product formed by O-demethylation, was 40 min in the female rat and 18.5 min in the male.

Effect of salicylamide and acetaminophen on dextromethorphan hydrobromide metabolism: possible pharmacological implications.

The effect of salicylamide and acetaminophen on the metabolic fate of dextrorphan, the primary metabolite of dextromethorphan, was studied in vivo in the rat. Plasma dextrorphan levels were measured at 5-min intervals up to 20 min and at longer intervals up to 2 hr after dextromethorphan hydrobromide was administered orally either alone or in combination with salicylamide and acetaminophen. The combination gave rise to higher plasma dextrorphan levels than did dextromethorphan hydrobromide alone at most sampling times.

Determination of dextrorphan in plasma and evaluation of bioavailability of dextromethorphan hydrobromide in humans.

A method is described for the estimation of dextrorphan, a metabolite of dextromethorphan, in plasma. The bioavailability of dextromethorphan hydrobromide after 30 mg po, as measured by the concentration of total (free and conjugated) dextrorphan in the plasma, was determined in six human volunteers with this procedure.