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5-Hydroxytryptophan

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Subjective Effects
Interactions
Tolerance
5-Hydroxytryptophan molecule structure5-Hydroxytryptophan molecule structure
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5-Hydroxytryptophan is a metabolic intermediate in serotonin biosynthesis1. It is produced from tryptophan2, and its decarboxylation yields serotonin2. Also known as oxitriptan3, it is a natural component of some dietary supplements4. It is used as a dietary supplement5 and, in some countries, for depression, sleep difficulties, or appetite suppression5. Oxitriptan could cause serotonin syndrome, particularly with concomitant use of antidepressant drug products6; after MDMA, TripSit advises waiting at least 12 hours.

Dosage & Duration

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Dosage

Doses are population estimates that vary widely between individuals.

Threshold25 mg
Light50-100 mg
Moderate100-200 mg
Strong200-300 mg
Heavy500+ mg

5-Hydroxytryptophan should not be taken concurrently with serotonergic substances. Following use of MDMA or similar serotonin-releasing agents, a minimum interval of 24 hours is advised before supplementation to reduce the risk of serotonin syndrome.

Duration

Onset30-60 minutes
Total4-6 hours

Subjective Effects

Subjective Effects not written up yet

Pharmacology

Pharmacodynamics

5-Hydroxytryptophan is a serotonin precursor that crosses the blood–brain barrier7 and is converted to serotonin by aromatic-L-amino-acid decarboxylase in a vitamin B6-dependent reaction8. Increased serotonin production in central nervous system tissue is considered the basis of its pharmacological action.7 In rats, intraperitoneal injections of 320 mg/kg 5-HTP induced a head-twitch response whose frequency was reduced by several putative 5-HT antagonists9, while further metabolism to N-methylated tryptamines may contribute to head twitches induced by 200 mg/kg intraperitoneal 5-HTP in wild-type and β-arrestin2 knock-out mice10; psychedelic effects of 5-HTP had not been reported in humans, according to a 2024 study.11

Pharmacokinetics

5-Hydroxytryptophan is decarboxylated to serotonin by aromatic-L-amino-acid decarboxylase in nervous tissue and the liver, and it crosses the blood–brain barrier whereas serotonin does not. Excess 5-hydroxytryptophan, particularly with vitamin B6, is thought to undergo further metabolism and excretion. Combining 5-HTP with carbidopa would be expected to increase bioavailability for brain penetration and decrease peripheral side effects through reduced peripheral decarboxylation of 5-HTP to serotonin12.

Interactions

Interactions not written up yet

An unlisted combination is an unknown one, not a safe one. Check a dedicated combination chart before mixing.

Check TripSit

Tolerance

Tolerance not written up yet

Harm Potential

Toxicity

Cardiovascular system

Prolonged use may carry a significant risk of heart valve disease. Rare adverse cardiovascular effects, typically reported at higher doses, include abnormal heartbeat, increased heart rate, and increased blood pressure.

Musculoskeletal and hematologic systems

Eosinophilia-myalgia syndrome, involving extreme muscle tenderness, myalgia, and blood abnormalities, has been associated with some 5-HTP supplements.

History & Culture

5-Hydroxytryptophan, also known medically as oxitriptan13, was described in a 2016 review as regulated as a food supplement in the United States.14 It is sold over the counter in the United States, United Kingdom, and Canada, while some European…

Legality

International

5-Hydroxytryptophan is not listed in the current INCB Yellow List under the 1961 Convention or Green List under the 1971 Convention, and it is not listed in either precursor table of the 1988 Convention.

By Country

Controlled / restricted3
Czech Republic flagCzech RepublicRestricted
Netherlands flagNetherlandsRestricted
Switzerland flagSwitzerlandRestricted
Prescription1
France flagFrancePrescription only
Legal / decriminalized2
Canada flagCanadaLegal (regulated)
Colombia flagColombiaLegal (regulated)
Not scheduled7
United States flagUnited StatesNot scheduled
Australia flagAustraliaNot scheduled
Brazil flagBrazilNot scheduled
Denmark flagDenmarkNot scheduled
Indonesia flagIndonesiaNot scheduled
Ireland flagIrelandNot scheduled
United Kingdom flagUnited KingdomNot scheduled

References

Citations

  1. 5-Hydroxytryptophan (5-HTP): Natural Occurrence, Analysis, Biosynthesis, Biotechnology, Physiology and Toxicology. International Journal of Molecular Sciences (2021). https://doi.org/10.3390/ijms220102811
  2. Serotonin a la carte: Supplementation with the serotonin precursor 5-hydroxytryptophan. Pharmacology & Therapeutics (2006). https://doi.org/10.1016/j.pharmthera.2005.06.00412
  3. Human Drug Compounding: Oxitriptan (5-HTP). U.S. Food and Drug Administration (2023). https://www.fda.gov/media/172413/download1
  4. 5-HTP. Memorial Sloan Kettering Cancer Center (n.d.). https://www.mskcc.org/cancer-care/integrative-medicine/herbs/5-htp-011
  5. Oxitriptan: Uses, Interactions, Mechanism of Action. DrugBank (n.d.). https://go.drugbank.com/drugs/DB0295912
  6. Bulk Drug Substances That Can Be Used to Compound Drug Products in Accordance With Section 503A. Federal Register (2019). https://public-inspection.federalregister.gov/2019-02367.pdf1
  7. 5-Hydroxytryptophan: a clinically-effective serotonin precursor. Alternative Medicine Review (1998). https://pubmed.ncbi.nlm.nih.gov/972708812
  8. Biochemical and Computational Approaches to Improve the Clinical Treatment of Dopa Decarboxylase-Related Diseases: An Overview. The Open Biochemistry Journal (2012). https://doi.org/10.2174/1874091x012060101311
  9. The head-twitch response to intraperitoneal injection of 5-hydroxytryptophan in the rat: antagonist effects of purported 5-hydroxytryptamine antagonists and of pirenperone, an LSD antagonist. Neuropharmacology (1983). https://doi.org/10.1016/0028-3908(83)90215-01
  10. Serotonin, But Not N-Methyltryptamines, Activates the Serotonin 2A Receptor Via a β-Arrestin2/Src/Akt Signaling Complex In Vivo. Journal of Neuroscience (2010). https://doi.org/10.1523/jneurosci.1665-10.20101

Further Reading

  1. Sprague et al. 1994 - Attenuation of 3,4-methylenedioxymethamphetamine (MDMA) induced neurotoxicity with the serotonin precursors tryptophan and 5-hydroxytryptophan

Article Status

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