European Journal of Clinical Pharmacology

, Volume 23, Issue 1, pp 81–86

Human pharmacokinetics of long term 5-hydroxytryptophan combined with decarboxylase inhibitors

  • I. Magnussen
  • M. H. Van Woert


L-5-Hydroxytryptophan (5HTP) and its major metabolites 5-hydroxytryptamine (5HT) and 5-hydroxyindoleaceticacid (5HIAA) were measured in blood and cerebrospinal fluid from neurological patients receiving steady state treatment with 5HTP. There was accumulation of 5HT in blood platelets and 5HIAA in plasma in all patients, despite concomitant administration of the L-aromatic amino acid decarboxylase inhibitors, carbidopa and benserazide. There was no correlation between the 5HTP dose and the circulating concentrations of the amino acid or its metabolites. Preliminary comparison of the biochemical and therapeutic effects of carbidopa versus benserazide suggest that 5HTP: carbidopa is superior to 5HTP: benserazide. A direct proportionality between plasma 5HTP concentrations and the levels of 5HTP in the lumbar cerebrospinal fluid was found. The binding to serum proteins of 5HTP in the clinically relevant concentration range of 10 to 100 µM was investigated; 19% of circulating 5HTP was bound to serum proteins. 5HTP did not displace protein-bound tryptophan in serum.

Key words

benserazide carbidopa serotonin 5HTP-treatment metabolism decarboxylase inhibitors cerebrospinal fluid metabolites protein binding 


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Copyright information

© Springer-Verlag 1982

Authors and Affiliations

  • I. Magnussen
    • 1
    • 2
  • M. H. Van Woert
    • 1
    • 2
  1. 1.Department of NeurologyMount Sinai School of MedicineNew YorkUSA
  2. 2.the Department of Neurology and the Research Laboratory for Metabolic Disorders, Department of Clinical ChemistryUniversity of AarhusAarhusDenmark

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