Interferon-alpha influences tryptophan metabolism without inducing psychiatric side effects.
BACKGROUND
Interferon-alpha (IFN-alpha) treatment is often associated with psychiatric side effects and has been found to lower the amount of tryptophan (TRP) available to the brain. The alterations in tryptophan metabolism might underlie the psychiatric side effects during treatment with IFN-alpha.


METHODS
In this study, 43 oncology patients treated with IFN-alpha were included. In order to study de novo depressions, depressed patients at baseline were excluded. Psychiatric evaluation comprising clinical judgment combined with a structured psychiatric interview and observer-based and self-report rating scales was performed at baseline and at 4 weeks, 8 weeks and 6 months after the start of treatment with IFN-alpha, and in the case of emerging psychopathology. Blood samples were drawn at the same evaluation times and assessed for concentrations of TRP, large neutral amino acids, kynurenine, 5-hydroxyindole acetic acid, neopterin and biopterin.


RESULTS
During treatment with IFN-alpha, several alterations in laboratory parameters occurred that were consistent with an increased degradation of peripheral TRP. Psychometric ratings revealed hardly any psychiatric changes. No consistent associations were found between changes in the laboratory assessments determined and the diverse psychiatric measures.


CONCLUSIONS
In this study, IFN-alpha was found to alter TRP metabolism without inducing psychiatric side effects. Therefore, a possible relationship between TRP metabolism and depression was not substantiated by this study.
Bannink
Marjolein
M
Department of Psychiatry, Erasmus Medical Center, Rotterdam, The Netherlands. m.bannink@erasmusmc.nl
Fekkes
Durk
D
Van Gool
Arthur R
AR
Kruit
Wim H J
WH
Sleijfer
Stefan
S
van der Holt
Bronno
B
Eggermont
Alexander M M
AM
Stoter
Gerrit
G
Hengeveld
Michiel W
MW
D000328:Adult; D000368:Aged; D001526:Behavioral Symptoms / Q000139:chemically induced*; D005260:Female; D006801:Humans; D007155:Immunologic Factors / Q000009:adverse effects*; D016898:Interferon-alpha / Q000009:adverse effects*; D008297:Male; D008545:Melanoma / Q000097:blood* / Q000188:drug therapy; D008875:Middle Aged; D011569:Psychiatric Status Rating Scales; D018709:Statistics, Nonparametric; D013997:Time Factors; D014364:Tryptophan / Q000097:blood*
D007155:Immunologic Factors; D016898:Interferon-alpha; D014364:Tryptophan