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Supplement × Prescription·Evidence index

Citalopram and L-Tryptophan: what the research found

PubMed indexes 8 records that name Citalopram and L-Tryptophan 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.

“Our results support a decreased breakdown of TRP via KYN pathway and a failure to modulate TRP-KYN pathway during citalopram-induced acute stress together with an increased vascular sensitivity in migraine. These mechanisms may provide useful drug targets for future drug development.”

Gecse et al. · 2022 · Human study · details

“Specifically, acute tryptophan depletion (ATD) produced a relatively larger NoGo response in the right IFG in subjects with low 5-HT2A BPP but reduced the NoGo response in those with high 5-HT2A BPP. These links between serotonergic function and response inhibition in healthy subjects may help to interpret serotonergic abnormalities underlying impulsivity in neuropsychiatric disorders.”

Macoveanu et al. · 2013 · Human study · details

“This finding suggests that 5-HTTLPR and TPH2 genes may act in concert to modulate the clinical response to citalopram among children and adolescents with depression and/or anxiety disorders.”

The research

8 studies naming Citalopram and L-Tryptophan.

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

Citalopram Neuroendocrine Challenge Shows Altered Tryptophan and Kynurenine Metabolism in Migraine.

Cells · 2022 · PMID 35883701

Randomized Controlled Trial

“Our results support a decreased breakdown of TRP via KYN pathway and a failure to modulate TRP-KYN pathway during citalopram-induced acute stress together with an increased vascular sensitivity in migraine. These mechanisms may provide useful drug targets for future drug development.”

Gecse et al. · From the abstract

Names both Citalopram and L-Tryptophan in its title.

Serotonin 2A receptors, citalopram and tryptophan-depletion: a multimodal imaging study of their interactions during response inhibition.

Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology · 2013 · PMID 23303045

Randomized Controlled Trial

“Specifically, acute tryptophan depletion (ATD) produced a relatively larger NoGo response in the right IFG in subjects with low 5-HT2A BPP but reduced the NoGo response in those with high 5-HT2A BPP. These links between serotonergic function and response inhibition in healthy subjects may help to interpret serotonergic abnormalities underlying impulsivity in neuropsychiatric disorders.”

Macoveanu et al. · From the abstract

Names both Citalopram and L-Tryptophan in its title.

Strain differences in basal and post-citalopram extracellular 5-HT in the mouse medial prefrontal cortex and dorsal hippocampus: relation with tryptophan hydroxylase-2 activity.

Journal of neurochemistry · 2007 · PMID 17666043

Comparative StudyAnimal study

“Although TRP could be a useful strategy to improve the antidepressant effect of citalopram (Cervo et al. 2005), particularly in subjects with low 5-HT synthesis, the contribution of serotonergic and non-serotonergic mechanisms to TRP's effect remains to be elucidated.”

Calcagno et al. · From the abstract

Names both Citalopram and L-Tryptophan in its title.

Serotonergic 'vulnerability' in affective disorder: a study of the tryptophan depletion test and relationships between peripheral and central serotonin indexes in citalopram-responders.

Acta psychiatrica Scandinavica · 1998 · PMID 9611088

Clinical TrialRandomized Controlled Trial20 participants

“There was a significant positive correlation in the baseline data between rated mood state and plasma cortisol and a significant inverse correlation between related mood state and plasma tryptophan concentration. Thus low mood appeared to be associated with low serotonin precursor availability as well as with high cortisol levels.”

Aberg-Wistedt et al. · From the abstract

Names both Citalopram and L-Tryptophan in its title.

Plasma tryptophan and tyrosine ratios to competing amino acids in relation to antidepressant response to citalopram and maprotiline. A preliminary study.

Psychopharmacology · 1986 · PMID 3080781

Clinical TrialComparative StudyControlled Clinical Trial14 participants

“The results suggest that the plasma Trp and Tyr ratios may be determinants of clinical improvement in depressed patients to treatment with citalopram and maprotiline. However, further studies are needed on larger patient samples to allow a firm conclusion.”

Møller et al. · From the abstract

Names both Citalopram and L-Tryptophan in its title.

Additive effects of 5-HTTLPR (serotonin transporter) and tryptophan hydroxylase 2 G-703T gene polymorphisms on the clinical response to citalopram among children and adolescents with depression and anxiety disorders.

Journal of child and adolescent psychopharmacology · 2013 · PMID 23510446

Human subjects

“This finding suggests that 5-HTTLPR and TPH2 genes may act in concert to modulate the clinical response to citalopram among children and adolescents with depression and/or anxiety disorders.”

Rotberg et al. · Authors' conclusion

Names both Citalopram and L-Tryptophan in its title.

Citalopram decreases tryptophan 2,3-dioxygenase activity and brain 5-HT turnover in swim stressed rats.

Pharmacological reports : PR · 2012 · PMID 22814009

Animal study

“Our findings support the hypothesis that acute citalopram administration increases tryptophan (by inhibiting TDO activity) availability for 5-HT synthesis and activates serotonergic neurotransmission in limbic brain areas in rats exposed to FST paradigm. The mechanism of action of citalopram in ameliorating social stress related depressive disorder in humans is discussed.”

Ara et al. · Authors' conclusion

Names both Citalopram and L-Tryptophan in its title.

Association between the tryptophan hydroxylase-1 gene A218C polymorphism and citalopram antidepressant response in a Korean population.

Progress in neuro-psychopharmacology & biological psychiatry · 2007 · PMID 16979275

Human subjects

“The remission rate to citalopram treatment was worse in MDD subjects with the TPH1 A/A and A/C genotypes than in those with the TPH1 C/C genotype. Our results suggest that the A218C polymorphism of the TPH1 gene serves as a modulator of antidepressant activity, especially in terms of treatment remission.”

Ham et al. · From the abstract

Names both Citalopram and L-Tryptophan 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

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