Kinetics of l-5-hydroxytryptophan in healthy subjects.
The kinetics of l-5-hydroxytryptophan (5-HTP) were studied in five volunteers after intravenous and oral administration of 5-HTP following pretreatment with carbidopa. In addition, the effect of pretreatment with carbidopa on metabolism and disposition of 5-HTP was studied in eight subjects. The kinetics of 5-HTP following a 20-minute linear infusion are adequately described by a biexponential function. The biological half-life of 5-HTP ranged from 2.2 to 7.4 hours, and the plasma clearance ranged from 0.10 to 0.23 1/kg/hour. The bioavailability of 5-HTP after oral administration in combination with carbidopa was calculated as 48% +/- 15 (mean +/- SD). The plasma concentrations of 5-HTP observed in this study displayed an unusual double peak in most subjects after oral administration. Pretreatment with carbidopa caused a significant increase in the extent of absorption of unchanged 5-HTP, and a significant reduction in the area under the plasma concentration-time curves of 5-hydroxyindoleacetic acid. Gastrointestinal side effects appeared to be related to the 5-HTP plasma concentration.
D006916:5-Hydroxytryptophan / Q000097:blood*; D000284:Administration, Oral; D000328:Adult; D002230:Carbidopa / Q000008:administration & dosage; D006207:Half-Life; D006801:Humans; D006897:Hydroxyindoleacetic Acid / Q000097:blood; D007263:Infusions, Parenteral; D007700:Kinetics; D008297:Male; D008657:Metabolic Clearance Rate / Q000187:drug effects; D012701:Serotonin / Q000097:blood
D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D006916:5-Hydroxytryptophan; D002230:Carbidopa