oxitriptan

5-HTP is sold over-the-counter in the United States, France, Canada, Singapore, the Netherlands, and the United Kingdom as a dietary supplement for use as an antidepressant, appetite suppressant, and sleep aid. It is also marketed in many European countries for the indication of major depressive disorder under the trade names Cincofarm, Levothym, Levotonine, Oxyfan, Telesol, Tript-OH, and Triptum.{{cite book | author = Swiss Pharmaceutical Society | title = Index Nominum 2000: International Drug Directory (Book with CD-ROM) | publisher = Medpharm Scientific Publishers | location = Boca Raton | year = 2000 | isbn = 978-3-88763-075-1 | url = https://books.google.com/books?id=5GpcTQD_L2oC&pg=PA773}}

A 2002 review concluded that although the data evaluated suggests that 5-HTP is more effective than placebo in the treatment of depression, the evidence was insufficient to be conclusive due to a lack of clinical data meeting the rigorous standards of the day.{{cite journal | vauthors = Shaw K, Turner J, Del Mar C | title = Tryptophan and 5-hydroxytryptophan for depression | journal = The Cochrane Database of Systematic Reviews | issue = 1 | pages = CD003198 | year = 2002 | volume = 2010 | pmid = 11869656 | doi = 10.1002/14651858.CD003198 | veditors = Shaw KA | url = https://espace.library.uq.edu.au/view/UQ:209937/UQ209937_OA.pdf }} More and larger studies using current methodologies are needed to determine if 5-HTP is truly effective in treating depression.{{cite web|url=http://www.umm.edu/altmed/articles/5-hydroxytryptophan-000283.htm|title=5-Hydroxytryptophan (5-HTP)|access-date=9 January 2012|publisher=University of Maryland Medical Center| archive-url=https://web.archive.org/web/20170625093048/http://umm.edu/health/medical/altmed/supplement/5hydroxytryptophan-5htp| archive-date=25 June 2017 | url-status=dead}}{{cite journal | vauthors = Iovieno N, Dalton ED, Fava M, Mischoulon D | title = Second-tier natural antidepressants: review and critique | journal = Journal of Affective Disorders | volume = 130 | issue = 3 | pages = 343–357 | date = May 2011 | pmid = 20579741 | doi = 10.1016/j.jad.2010.06.010 }} In small, controlled trials, 5-HTP has also been reported to augment the antidepressant efficacy of the antidepressant clomipramine.{{cite journal | vauthors = van Praag HM | title = Serotonin precursors in the treatment of depression | journal = Advances in Biochemical Psychopharmacology | volume = 34 | pages = 259–286 | year = 1982 | pmid = 6753514 }}{{cite journal | vauthors = van Praag HM, van den Burg W, Bos ER, Dols LC | title = 5-hydroxytryptophan in combination with clomipramine in "therapy-resistant" depressions | journal = Psychopharmacologia | volume = 38 | issue = 3 | pages = 267–269 | year = 1974 | pmid = 4547418 | doi = 10.1007/BF00421379 | s2cid = 11048888 }}{{cite journal | vauthors = Nardini M, De Stefano R, Iannuccelli M, Borghesi R, Battistini N | title = Treatment of depression with L-5-hydroxytryptophan combined with chlorimipramine, a double-blind study | journal = International Journal of Clinical Pharmacology Research | volume = 3 | issue = 4 | pages = 239–250 | year = 1983 | pmid = 6381336 }} A 2020 meta-analysis found oral 5-HTP supplementation had a large effect size on depression symptom severity. However, the included studies were considered relatively weak and the methods and treatment duration varied between the seven studies examined.{{cite journal | vauthors = Javelle F, Lampit A, Bloch W, Häussermann P, Johnson SL, Zimmer P | title = Effects of 5-hydroxytryptophan on distinct types of depression: a systematic review and meta-analysis | journal = Nutrition Reviews | volume = 78 | issue = 1 | pages = 77–88 | date = January 2020 | pmid = 31504850 | doi = 10.1093/nutrit/nuz039 }}

At high doses, or in combination with carbidopa, 5-HTP has been used to treat obesity (by promoting weight loss).{{cite journal | vauthors = Halpern B, Oliveira ES, Faria AM, Halpern A, Melo ME, Cercato C, Mancini MC | title = Combinations of drugs in the Treatment of Obesity | journal = Pharmaceuticals | volume = 3 | issue = 8 | pages = 2398–2415 | date = July 2010 | pmid = 27713360 | pmc = 4033931 | doi = 10.3390/ph3082398 | doi-access = free }}{{cite journal | vauthors = Hendricks EJ | title = Off-label drugs for weight management | journal = Diabetes, Metabolic Syndrome and Obesity: Targets and Therapy| volume = 10 | pages = 223–234 | date = 2017 | pmid = 28652791 | pmc = 5473499 | doi = 10.2147/DMSO.S95299 | doi-access = free }}

MDMA is an empathogenic-entactogenic and serotonergic psychotropic drug used primarily for recreational, though sometimes also therapeutic, purposes. Among users of MDMA, the serotonergic effects of the drug are often of particular interest and concern: After consuming MDMA, serotonin concentrations are greatly reduced in the brain. 5-HTP is necessary for serotonin production and its concentrations in the brain also decrease after taking MDMA.

Potential side effects of 5-HTP include heartburn, abdominal pain, nausea, vomiting, diarrhea, drowsiness, sexual problems, vivid dreams or nightmares, and muscle problems.{{cite web|url=https://www.nlm.nih.gov/medlineplus/druginfo/natural/794.html |title=5-HTP |work=U.S. National Library of Medicine |access-date=7 June 2015}} Serotonin syndrome can occur.

Because 5-HTP has not been thoroughly studied in a clinical setting, possible side effects and interactions with other drugs are not well known. According to the US National Library of Medicine, 5-HTP has not been associated with serotonin syndrome or any serious adverse events in humans.{{Cite web | url=https://pubchem.ncbi.nlm.nih.gov/compound/5-Hydroxytryptophan#section=Toxicity |title = 5-Hydroxytryptophan, C11H12N2O3, CID 144 - PubChem}} Across multiple studies, 5-HTP has also been reported to not cause any noticeable hematological or cardiovascular changes.{{cite journal | vauthors = Byerley WF, Judd LL, Reimherr FW, Grosser BI | date = Jun 1987 | title = 5-Hydroxytryptophan: a review of its antidepressant efficacy and adverse effects | journal = J Clin Psychopharmacol | volume = 7 | issue = 3| pages = 127–37 | pmid = 3298325 | doi = 10.1097/00004714-198706000-00002 }} 5-HTP had also been associated with eosinophilia, but later studies have not found any causal connection.{{cite journal | vauthors = Das YT, Bagchi M, Bagchi D, Preuss HG | year = 2004 | title = Safety of 5-hydroxy-L-tryptophan | journal = Toxicol. Lett. | volume = 150 | issue = 1| pages = 111–22 | pmid = 15068828 | doi = 10.1016/j.toxlet.2003.12.070 }}

When combined with antidepressants of the MAOI or SSRI class, very high parenteral doses of 5-HTP can cause acute serotonin syndrome in rats.{{cite journal | vauthors = Ma Z, Zhang G, Jenney C, Krishnamoorthy S, Tao R | title = Characterization of serotonin-toxicity syndrome (toxidrome) elicited by 5-hydroxy-l-tryptophan in clorgyline-pretreated rats | journal = European Journal of Pharmacology | volume = 588 | issue = 2–3 | pages = 198–206 | date = July 2008 | pmid = 18499101 | pmc = 4242171 | doi = 10.1016/j.ejphar.2008.04.004 }}{{cite journal | vauthors = Izumi T, Iwamoto N, Kitaichi Y, Kato A, Inoue T, Koyama T | title = Effects of co-administration of a selective serotonin reuptake inhibitor and monoamine oxidase inhibitors on 5-HT-related behavior in rats | journal = European Journal of Pharmacology | volume = 532 | issue = 3 | pages = 258–64 | date = February 2006 | pmid = 16488409 | doi = 10.1016/j.ejphar.2005.12.075 }} It is unclear if such findings have clinical relevance, as most drugs will cause serious adverse events or death in rodents at very high doses. In humans, 5-HTP has never been clinically associated with serotonin syndrome – although a case report suggests 5-HTP can precipitate mania when added to an MAOI.{{cite journal | vauthors = Pardo JV | title = Mania following addition of hydroxytryptophan to monoamine oxidase inhibitor | journal = General Hospital Psychiatry | volume = 34 | issue = 1 | pages = 102.e13–4 | date = 2012 | pmid = 21963353 | pmc = 3253963 | doi = 10.1016/j.genhosppsych.2011.08.014 }}

When combined with carbidopa (as a treatment for symptoms of Parkinson's disease), 5-HTP causes nausea and vomiting; however, this can be alleviated via administration of granisetron.{{cite journal | vauthors = Jacobs GE, Kamerling IM, de Kam ML, Derijk RH, van Pelt J, Zitman FG, van Gerven JM | title = Enhanced tolerability of the 5-hydroxytryptophane challenge test combined with granisetron | journal = Journal of Psychopharmacology | volume = 24 | issue = 1 | pages = 65–72 | date = January 2010 | pmid = 18719048 | doi = 10.1177/0269881108094299 | s2cid = 23562225 }} Cases of scleroderma-like illness have been reported in patients using carbidopa and 5-HTP.{{cite web|url=http://www.truestarhealth.com/Notes/1339004.html |title=Carbidopa/Levodopa |publisher=Truestarhealth.com |access-date=2014-01-09 |url-status=dead |archive-url=https://web.archive.org/web/20140108185248/http://www.truestarhealth.com/Notes/1339004.html |archive-date=8 January 2014 |df=dmy }}

Oral 5-HTP results in an increase in urinary 5-HIAA, a serotonin metabolite, indicating that 5-HTP is peripherally metabolized to serotonin, which is then metabolized. This might cause false positive results in tests looking for carcinoid syndrome.{{cite journal | vauthors = Joy T, Walsh G, Tokmakejian S, Van Uum SH | title = Increase of urinary 5-hydroxyindoleacetic acid excretion but not serum chromogranin A following over-the-counter 5-hydroxytryptophan intake | journal = Canadian Journal of Gastroenterology | volume = 22 | issue = 1 | pages = 49–53 | date = January 2008 | pmid = 18209781 | pmc = 2659120 | doi = 10.1155/2008/472159 | doi-access = free }}{{cite journal | vauthors = Hallin ML, Mahmoud K, Viswanath A, Gama R | title = 'Sweet Dreams', 'Happy Days' and elevated 24-h urine 5-hydroxyindoleacetic acid excretion | journal = Annals of Clinical Biochemistry | volume = 50 | issue = Pt 1 | pages = 80–2 | date = January 2013 | pmid = 23086978 | doi = 10.1258/acb.2012.012041 | s2cid = 207193834 | doi-access = free }} Due to the conversion of 5-HTP into serotonin by the liver, there could be a risk of heart valve disease from serotonin's effect on the heart, as based on preclinical findings.{{cite journal | vauthors = Gustafsson BI, Tømmerås K, Nordrum I, Loennechen JP, Brunsvik A, Solligård E, Fossmark R, Bakke I, Syversen U, Waldum H | title = Long-term serotonin administration induces heart valve disease in rats | journal = Circulation | volume = 111 | issue = 12 | pages = 1517–22 | date = March 2005 | pmid = 15781732 | doi = 10.1161/01.CIR.0000159356.42064.48 | s2cid = 3035838 | doi-access = free }}{{cite journal | vauthors = Xu J, Jian B, Chu R, Lu Z, Li Q, Dunlop J, Rosenzweig-Lipson S, McGonigle P, Levy RJ, Liang B | title = Serotonin mechanisms in heart valve disease II: the 5-HT2 receptor and its signaling pathway in aortic valve interstitial cells | journal = The American Journal of Pathology | volume = 161 | issue = 6 | pages = 2209–18 | date = December 2002 | pmid = 12466135 | pmc = 1850896 | doi = 10.1016/S0002-9440(10)64497-5 }} However, 5-HTP has not been associated with cardiac toxicity in humans.{{cite journal | vauthors = Turner EH, Loftis JM, Blackwell AD | date = Mar 2006 | title = Serotonin a la carte: supplementation with the serotonin precursor 5-hydroxytryptophan | url = http://www.escholarship.org/uc/item/58h866d5| journal = Pharmacol. Ther. | volume = 109 | issue = 3| pages = 325–38 | pmid = 16023217 | doi = 10.1016/j.pharmthera.2005.06.004 | s2cid = 2563606 }}

It has been suggested that 5-HTP may cause eosinophilia-myalgia syndrome (EMS), a serious condition which results in extreme muscle tenderness, myalgia, and blood abnormalities. However, there is evidence to show that EMS was likely caused by a contaminant in certain 5-HTP supplements.{{cite journal | vauthors = Michelson D, Page SW, Casey R, Trucksess MW, Love LA, Milstien S, Wilson C, Massaquoi SG, Crofford LJ, Hallett M | title = An eosinophilia-myalgia syndrome related disorder associated with exposure to L-5-hydroxytryptophan | journal = The Journal of Rheumatology | volume = 21 | issue = 12 | pages = 2261–5 | date = December 1994 | pmid = 7699627 }}

The psychoactive action of 5-HTP is derived from its increase in production of serotonin in central nervous system tissue.{{cite web|url=http://www.webmd.com/vitamins-supplements/ingredientmono-794-5-HTP.aspx?activeIngredientId=794&activeIngredientName=5-HTP|title=5-HTP: Uses, Side Effects, Interactions and Warnings - WebMD|access-date=2009-10-05| archive-url= https://web.archive.org/web/20091116091605/http://www.webmd.com/vitamins-supplements/ingredientmono-794-5-HTP.aspx?activeIngredientId=794&activeIngredientName=5-HTP| archive-date= 16 November 2009 | url-status= live}}

Image:trp-5ht-pathway.svg

Research shows that co-administration with carbidopa greatly increases plasma 5-HTP levels.{{cite journal | vauthors = Magnussen I, Jensen TS, Rand JH, Van Woert MH | title = Plasma accumulation of metabolism of orally administered single dose L-5-hydroxytryptophan in man | journal = Acta Pharmacologica et Toxicologica | volume = 49 | issue = 3 | pages = 184–9 | date = September 1981 | pmid = 6175178 | doi = 10.1111/j.1600-0773.1981.tb00890.x }}

Other studies have indicated the risk of a scleroderma-like condition resulting from the combination of 5-HTP and carbidopa.{{cite journal | vauthors = Sternberg EM, Van Woert MH, Young SN, Magnussen I, Baker H, Gauthier S, Osterland CK | title = Development of a scleroderma-like illness during therapy with L-5-hydroxytryptophan and carbidopa | journal = The New England Journal of Medicine | volume = 303 | issue = 14 | pages = 782–7 | date = October 1980 | pmid = 6997735 | doi = 10.1056/NEJM198010023031403 }}

After oral administration, 5-HTP is absorbed by the upper intestine. The mode of absorption is not known, but presumably involves active transport via amino acid transporters. 5-HTP is adequately absorbed via oral cavity.{{cite journal | vauthors = Rondanelli M, Opizzi A, Faliva M, Bucci M, Perna S | title = Relationship between the absorption of 5-hydroxytryptophan from an integrated diet, by means of Griffonia simplicifolia extract, and the effect on satiety in overweight females after oral spray administration | journal = Eat Weight Disord. | volume = 17 | issue = 1 | date = March 2012 | doi = 10.3275/8165 | pmid = 22142813 | pages = e22-8 | doi-broken-date = 2 December 2024 | s2cid = 10651414 }} With a decarboxylase inhibitor, the bioavailability of 5-HTP can be higher than 50%.{{cite journal | vauthors = Magnussen I, Nielsen-Kudsk F | title = Bioavailability and related pharmacokinetics in man of orally administered L-5-hydroxytryptophan in steady state | journal = Acta Pharmacologica et Toxicologica | volume = 46 | issue = 4 | pages = 257–62 | date = April 1980 | pmid = 6966118 | doi = 10.1111/j.1600-0773.1980.tb02451.x }}

5-HTP is rapidly absorbed with a t_max of {{nowrap|≈1.5{{tsp}}h}}, and rapidly eliminated with a half-life of {{nowrap|≈1.5{{hsp}}{{ndash}}{{hsp}}2{{tsp}}h}}. Co-administration of a decarboxylase inhibitor (e.g., carbidopa, benserazide) doubles the half-life of 5-HTP to {{nowrap|≈{{hsp}}3{{hsp}}{{ndash}}{{hsp}}4{{tsp}}h}},{{cite journal | vauthors = Magnussen I, Engbaek F | title = The effects of aromatic amino acid decarboxylase inhibitors on plasma concentrations of 5-hydroxytryptophan in man | journal = Acta Pharmacologica et Toxicologica | volume = 43 | issue = 1 | pages = 36–42 | date = July 1978 | pmid = 309271 | doi = 10.1111/j.1600-0773.1978.tb02229.x }} and enhances exposure several-fold, depending on the dosing regimen.{{cite journal | vauthors = Westenberg HG, Gerritsen TW, Meijer BA, van Praag HM | title = Kinetics of l-5-hydroxytryptophan in healthy subjects | journal = Psychiatry Research | volume = 7 | issue = 3 | pages = 373–85 | date = December 1982 | pmid = 6187038 | doi = 10.1016/0165-1781(82)90074-9 | s2cid = 45003287 }}

5-HTP's short half-life (<2 hours){{cite journal | vauthors = Gijsman HJ, van Gerven JM, de Kam ML, Schoemaker RC, Pieters MS, Weemaes M, de Rijk R, van der Post J, Cohen AF | title = Placebo-controlled comparison of three dose-regimens of 5-hydroxytryptophan challenge test in healthy volunteers | journal = Journal of Clinical Psychopharmacology | volume = 22 | issue = 2 | pages = 183–189 | date = April 2002 | pmid = 11910264 | doi = 10.1097/00004714-200204000-00012 | s2cid = 37414452 }} may inherently limit its therapeutic potential,{{cite journal | vauthors = Jacobsen JP, Krystal AD, Krishnan KR, Caron MG | title = Adjunctive 5-Hydroxytryptophan Slow-Release for Treatment-Resistant Depression: Clinical and Preclinical Rationale | journal = Trends in Pharmacological Sciences | volume = 37 | issue = 11 | pages = 933–944 | date = November 2016 | pmid = 27692695 | pmc = 5728156 | doi = 10.1016/j.tips.2016.09.001 }} as systemic 5-HTP exposure levels will fluctuate substantially even with relatively frequent dosing. Such exposure fluctuations are usually associated with increased adverse event burdens resulting from C_max (time to maximal systemic concentration) drug spikes, and decreased clinical efficacy resulting from sub-therapeutic exposure for large parts of the day, when taken as a single dose unit or at intervals significantly larger than C_max. It has been proposed that 5-HTP dosage forms achieving prolonged delivery would be more effective, as has been demonstrated many times with other pharmaceuticals with short durations of action.{{cite journal | vauthors = Thombre AG | title = Assessment of the feasibility of oral controlled release in an exploratory development setting | journal = Drug Discovery Today | volume = 10 | issue = 17 | pages = 1159–1166 | date = September 2005 | pmid = 16182208 | doi = 10.1016/S1359-6446(05)03551-8 }} For example, controlled-release oxycodone (OxyContin) or morphine (MS-Contin) are intended to, via novel delivery mechanisms, permit pain relief for up to twelve hours with an active ingredient which only provides relief for 3 to 6{{nbsp}}hours. However, the inherent variability amongst different people with respect to drug metabolism makes this task challenging.

Oxitriptan is the generic name of the drug and its {{Abbrlink|INN|International Nonproprietary Name}}.{{cite book | vauthors = Elks J | title=The Dictionary of Drugs: Chemical Data: Chemical Data, Structures and Bibliographies | publisher=Springer US | year=2014 | isbn=978-1-4757-2085-3 | url=https://books.google.com/books?id=0vXTBwAAQBAJ&pg=PA670 | access-date=30 September 2024 | page=670}}{{cite book | vauthors = Morton IK, Hall JM | title=Concise Dictionary of Pharmacological Agents: Properties and Synonyms | publisher=Springer Netherlands | year=2012 | isbn=978-94-011-4439-1 | url=https://books.google.com/books?id=tsjrCAAAQBAJ&pg=PA147 | access-date=30 September 2024 | page=147}} Brand names of oxitriptan include Cincofarm, Levothym, Levotonine, Oxyfan, Telesol, Tript-OH, and Triptum.{{cite book | author = Swiss Pharmaceutical Society | title = Index Nominum 2000: International Drug Directory (Book with CD-ROM) | publisher = Medpharm Scientific Publishers | location = Boca Raton | year = 2000 | isbn = 978-3-88763-075-1 | url = https://books.google.com/books?id=5GpcTQD_L2oC&pg=PA773}}

There are currently no approved drug products containing 5-HTP approved by the FDA.{{Cite web | url=https://www.accessdata.fda.gov/Scripts/cder/ob/index.cfm |title = Orange Book: Approved Drug Products with Therapeutic Equivalence Evaluations}} All available 5-HTP products are nutraceuticals and are as such not regulated or verified for purity, integrity, or clinical efficacy or safety, mandating caution regarding human consumption.{{Cite web | url=https://medlineplus.gov/druginfo/natural/794.html |title = 5-HTP: MedlinePlus Supplements | work = MedlinePlus | publisher = U.S. National Library of Medicine }}

As of 25 August 2020, Hungary added 5-HTP to the controlled psychoactive substances list, prohibiting production, sale, import, storage and use, becoming the first country to do so.[https://magyarkozlony.hu/hivatalos-lapok/fsmDhb9y0CRKX2SkxRDw5f37b222dc2d1/dokumentumok/bc9ef7aef40a107a518ab17e1ac35adf2735e291/letoltes MAGYARORSZÁG HIVATALOS LAPJA]. Retrieved 2021-04-28.

The seeds of the Griffonia simplicifolia, a climbing shrub native to West Africa and Central Africa, are used as an herbal supplement for their 5-HTP content.{{cite web |title=5-Hydroxytryptophan (5-HTP) |publisher=University of Maryland Medical Center |url=http://www.umm.edu/altmed/articles/5-hydroxytryptophan-000283.htm |work=A.D.A.M., Inc.}} Animated Dissection of Anatomy for Medicine, Inc. (A.D.A.M., Inc.) provided health and benefits information and technology to healthcare organizations, employers, consumers, and educational institutions{{cite journal | vauthors = Emanuele E, Bertona M, Minoretti P, Geroldi D | title = An open-label trial of L-5-hydroxytryptophan in subjects with romantic stress | journal = Neuro Endocrinology Letters | volume = 31 | issue = 5 | pages = 663–6 | year = 2010 | pmid = 21178946 }}{{citation | url=https://pubchem.ncbi.nlm.nih.gov/compound/439280 | title=5-hydroxy-L-tryptophan | work=National Center for Biotechnology Information | series=PubChem Compound Database | date=September 2004 }}CID=439280 In one 2010 trial, Griffonia simplicifolia extract appeared to increase satiety in overweight women.{{cite journal | vauthors = Rondanelli M, Opizzi A, Faliva M, Bucci M, Perna S | title = Relationship between the absorption of 5-hydroxytryptophan from an integrated diet, by means of Griffonia simplicifolia extract, and the effect on satiety in overweight females after oral spray administration | journal = Eating and Weight Disorders | volume = 17 | issue = 1 | pages = e22–8 | date = March 2012 | pmid = 22142813 | doi = 10.3275/8165 | doi-broken-date = 2 December 2024 | s2cid = 10651414 }}

In clinical trials of various design, 5-HTP has also been reported to treat fibromyalgia,{{cite journal | vauthors = Caruso I, Sarzi Puttini P, Cazzola M, Azzolini V | year = 1990 | title = Double-blind study of 5-hydroxytryptophan versus placebo in the treatment of primary fibromyalgia syndrome | journal = J Int Med Res | volume = 18 | issue = 3| pages = 201–209 | pmid = 2193835 | doi = 10.1177/030006059001800304 | s2cid = 27586915 }} myoclonus,{{cite journal | pmid = 6969054 | doi=10.1002/ana.410070611 | volume=7 | title=Treatment of myoclonus with L-5-hydroxytryptophan and carbidopa: clinical, electrophysiological, and biochemical observations | year=1980 | journal=Ann Neurol | pages=570–576 | vauthors=Thal LJ, Sharpless NS, Wolfson L, Katzman R | issue=6 | s2cid=11647568 }} migraine,{{cite journal | vauthors = Boiardi A, Crenna P, Merati B, Negri S, Tansini E, Bussone G | year = 1981 | title = 5-OH-Tryptophane in migraine: clinical and neurophysiological considerations | journal = J Neurol | volume = 225 | issue = 1| pages = 41–46 | pmid = 6164755 | doi = 10.1007/bf00313460 | s2cid = 2424064 }} and cerebellar ataxia.{{cite journal | vauthors = Trouillas P, Brudon F, Adeleine P | date = Nov 1988 | title = Improvement of cerebellar ataxia with levorotatory form of 5-hydroxytryptophan. A double-blind study with quantified data processing | journal = Arch Neurol | volume = 45 | issue = 11| pages = 1217–1222 | pmid = 3190503 | doi = 10.1001/archneur.1988.00520350055016 }} However, these clinical findings, as for all therapeutic findings with 5-HTP, are preliminary and need confirmation in larger trials.

A combination of oxitriptan and carbidopa, oxitriptan/carbidopa, is being developed for the potential treatment of depression.

5-HTP's short half-life is impractical for chronic drug therapy. Research conducted at Duke University in mice has demonstrated that 5-HTP when administered as slow-release appears to gain drug properties.{{cite journal | vauthors = Jacobsen JP, Rudder ML, Roberts W, Royer EL, Robinson TJ, Oh A, Spasojevic I, Sachs BD, Caron MG | date = Aug 2016 | title = SSRI Augmentation by 5-Hydroxytryptophan Slow Release: Mouse Pharmacodynamic Proof of Concept | journal = Neuropsychopharmacology | volume = 41 | issue = 9| pages = 2324–34 | doi = 10.1038/npp.2016.35 | pmid = 26932820 | pmc = 4946063 }} Slow-release delivery attenuates or abolishes the peaks and valleys in 5-HTP exposure during treatment.{{cite journal | vauthors = Thombre AG | year = 2005 | title = Assessment of the feasibility of oral controlled release in an exploratory development setting | journal = Drug Discov Today | volume = 10 | issue = 17| pages = 1159–66 | pmid = 16182208 | doi = 10.1016/S1359-6446(05)03551-8 }} Slow-release delivery of 5-HTP markedly improved the safety profile of 5-HTP and conferred stable plasma exposure of 5-HTP and strong and sustained enhancement of brain serotonin function. This discovery indicates that 5-HTP slow-release medications represent a new avenue for treatment of brain disorders responsive to serotonergic enhancement.

• Tryptophan
• α-Methyl-5-hydroxytryptophan

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Category:5-Hydroxytryptamines

Category:Monoamine precursors

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