Single oral dose pharmacokinetics of amitriptylinoxide and amitriptyline in humans.

Eleven healthy volunteers were examined in a pharmacokinetic study. After oral administration of 50 mg amitriptylinoxide or 50 mg amitriptyline the plasma levels of amitriptylinoxide and its main metabolites amitriptyline and nortriptyline were investigated over 24 hours. The results indicate that amitriptylinoxide is more rapidly absorbed than amitriptyline and eliminated with a mean half-life of 1.5 hours. The change with time in the levels of amitriptyline formed from the oxide is similar to that of amitriptyline after ingestion of amitriptyline. However, the plasma concentration of amitriptylinoxide, reflected by the area under the time curve (AUC), exceeds that of its metabolite amitriptyline twelvefold.