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Supplement × Prescription·Evidence index

L-Tryptophan and Paroxetine: what the research found

PubMed indexes 8 records that name L-Tryptophan and Paroxetine together, either in the title or in an interaction, co-administration, or pharmacokinetic context. The key findings come first, in the authors’ own words, followed by every study with its design and PubMed link.

A summary of published research, not medical advice. A pharmacist can check any combination against your full list of medicines and supplements.

Key findings

What the studies concluded.

Reviews and human studies first. Each quote is the authors’ own conclusion about their study, not a NutriStack assessment, and a single study is not a consensus.

“The results suggest that reduced TRP availability plays a role in IFN-alpha-induced depressive symptoms, and paroxetine, although not altering the KYN or neopterin response to IFN-alpha, attenuates the behavioral consequences of IFN-alpha-mediated TRP depletion.”

Capuron et al. · 2003 · Human study · details

“Other variables, such as sex, diagnosis, presence of psychotic features, severity of depressive symptomatology at baseline and paroxetine plasma level, were not associated with the outcome. TPH gene variants are therefore a possible modulator of paroxetine antidepressant activity.”

Serretti et al. · 2001 · Human study · details

“The improvement in the paroxetine group was significantly inversely correlated with the Trp concentration but not with the ratio Trp/LNAA. The findings accord with previous trials of various antidepressant treatments, in which about 25% of the variance in therapeutic response associates with pretreatment plasma amino acid profiles.”

The research

8 studies naming L-Tryptophan and Paroxetine.

Strongest relevance first: papers naming both substances in the title, then human trials and systematic reviews.

Interferon-alpha-induced changes in tryptophan metabolism. relationship to depression and paroxetine treatment.

Biological psychiatry · 2003 · PMID 14573318

Clinical TrialRandomized Controlled Trial

“The results suggest that reduced TRP availability plays a role in IFN-alpha-induced depressive symptoms, and paroxetine, although not altering the KYN or neopterin response to IFN-alpha, attenuates the behavioral consequences of IFN-alpha-mediated TRP depletion.”

Capuron et al. · Authors' conclusion

Names both L-Tryptophan and Paroxetine in its title.

Tryptophan hydroxylase gene associated with paroxetine antidepressant activity.

European neuropsychopharmacology : the journal of the European College of Neuropsychopharmacology · 2001 · PMID 11597824

Clinical TrialRandomized Controlled Trial

“Other variables, such as sex, diagnosis, presence of psychotic features, severity of depressive symptomatology at baseline and paroxetine plasma level, were not associated with the outcome. TPH gene variants are therefore a possible modulator of paroxetine antidepressant activity.”

Serretti et al. · From the abstract

Names both L-Tryptophan and Paroxetine in its title.

Plasma ratio tryptophan/neutral amino acids in relation to clinical response to paroxetine and clomipramine in patients with major depression.

Journal of affective disorders · 1990 · PMID 2136870

Clinical TrialComparative StudyControlled Clinical Trial

“The improvement in the paroxetine group was significantly inversely correlated with the Trp concentration but not with the ratio Trp/LNAA. The findings accord with previous trials of various antidepressant treatments, in which about 25% of the variance in therapeutic response associates with pretreatment plasma amino acid profiles.”

Møller et al. · From the abstract

Names both L-Tryptophan and Paroxetine in its title.

Reduction in serotonin synthesis following acute and chronic treatments with paroxetine, a selective serotonin reuptake inhibitor, in rat brain: an autoradiographic study with alpha-[14C]methyl-L-tryptophan(2).

Biochemical pharmacology · 2001 · PMID 11728384

Animal study

“There was a marked decrease (39-69%) in 5-HT synthesis in every structure examined. In conclusion, the present data suggest that the effects of paroxetine on 5-HT synthesis in the cerebral cortex are different from its effects in the cell body area of the brainstem.”

Yamane et al. · From the abstract

Names both L-Tryptophan and Paroxetine in its title.

Limitations

What this evidence cannot tell you.

Search-based evidence indexes have real limits, and it is worth being explicit about them:

How to read this page

A literature summary, not guidance.

NutriStack

Track what you actually take.

NutriStack is a free iPhone app for organising a supplement routine: what you take, when, and what the published record says about it. Its exploratory interaction checker covers L-Tryptophan, Paroxetine, and several hundred other substances.

Log your routine, get reminders at the times you choose, and scan a label to add a product. The checker is a research and organisation tool, not a clinical decision aid.

NutriStack is an informational and organizational tool, not a medical service, and not a substitute for professional advice. Always consult a qualified healthcare professional before starting, stopping, or changing any supplement or medication.