5-Hydroxytryptophan
Encyclopedia
5-Hydroxytryptophan also known as oxitriptan (INN
), is a naturally occurring
amino acid
and chemical
precursor
as well as metabolic intermediate
in the biosynthesis
of the neurotransmitter
s serotonin
and melatonin
from tryptophan
.
5-HTP is sold over-the-counter in the United Kingdom
, United States
and Canada
as a dietary supplement
for use as an antidepressant
, appetite suppressant, and sleep aid, and is also marketed in many Europe
an countries for the indication of major depression under trade names like Cincofarm, Levothym, Levotonine, Oxyfan, Telesol, Tript-OH, and Triptum. Several double-blind
placebo
-controlled clinical trial
s have demonstrated the effectiveness of 5-HTP in the treatment of depression, though a lack of high quality studies has been noted.
to serotonin
(5-hydroxytryptamine or 5-HT) by the enzyme
aromatic-L-amino-acid decarboxylase with the help of vitamin B6
. This reaction occurs both in nervous tissue and in the liver. 5-HTP crosses the blood-brain barrier
, while 5-HT does not. Excess 5-HTP, especially when administered with Vitamin B6
, is thought to be metabolized and excreted.
tissue. More specifically, 5-HTP increases the production of serotonin. Thus, it has been used to treat conditions such as depression, for which the lack of serotonin is thought to be a contributing factor.
Research shows that co-administration with carbidopa
greatly increases plasma
5-HTP levels. However, several studies have reported that 5-HTP is effective even without a peripheral decarboxylase inhibitor (e.g. carbidopa).
Other studies have indicated the risk of a scleroderma
-like condition resulting from the combination of 5-HTP and carbidopa.
, the United Kingdom
, and Canada
as a dietary supplement
for use as an antidepressant
, appetite suppressant, and sleep aid. 5-HTP in supplement form is typically sold in 50 mg or 100 mg gelatin
or vegetarian capsules. It is usually sourced from the seeds of Griffonia simplicifolia
.
5-HTP has been studied and shown to be of benefit in the following conditions: primary fibromyalgia
syndrome, Friedreich's ataxia
, depression, anxiety, binge eating
associated with obesity, and insomnia. There is no statistically significant difference between 5-HTP and placebo in treating chronic headaches (primary or otherwise).
A 2001 meta-analysis found that of 108 studies on 5-HTP published between 1966 and 2000, only two met the authors' quality standards for inclusion. The two studies that were deemed of sufficient quality did not deal with 5-HTP exclusively, instead combining results for 5-HTP and tryptophan
, so the results may not be completely applicable for 5-HTP alone. While the combined analysis of the two 5-HTP and tryptophan studies showed significant effectiveness over placebo in treating depression, the authors state that overall "the evidence was of insufficient quality to be conclusive". They also state that "because alternative antidepressants exist which have been proven to be effective and safe, the clinical usefulness of 5-HTP and tryptophan is limited at present".
Administered serotonin has been shown to increase the risk of heart valve disease in animals. 5-HTP has not been subjected to this test. 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 a false positive test in tests looking for carcinoid syndrome
.
5-HTP can cause hypertension
by increasing plasma renin activity, when not co-administered with a peripheral
aromatic L-amino acid decarboxylase
inhibitor
, such as carbidopa
or benserazide
.
Direct and indirect evidence for possible yet unproven risks and side effects associated with 5-HTP when overdosed:
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 caused by a contaminant in early 5-HTP supplements, before the introduction of the current Good Manufacturing Practices by the United States FDA in 2007. Many countries now employ similar regulation..
International Nonproprietary Name
An International Nonproprietary Name is the official nonproprietary or generic name given to a pharmaceutical substance, as designated by the World Health Organization...
), is a naturally occurring
Natural product
A natural product is a chemical compound or substance produced by a living organism - found in nature that usually has a pharmacological or biological activity for use in pharmaceutical drug discovery and drug design...
amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
and chemical
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
precursor
Precursor (chemistry)
In chemistry, a precursor is a compound that participates in the chemical reaction that produces another compound. In biochemistry, the term "precursor" is used more specifically to refer to a chemical compound preceding another in a metabolic pathway....
as well as metabolic intermediate
Metabolic intermediate
Metabolic intermediates refers to molecules which are the precursors or metabolites of biologically significant molecules.Although these intermediates are of relatively minor direct importance to cellular function, they can play important roles in the allosteric regulation of enzymes.-Clinical...
in the biosynthesis
Biosynthesis
Biosynthesis is an enzyme-catalyzed process in cells of living organisms by which substrates are converted to more complex products. The biosynthesis process often consists of several enzymatic steps in which the product of one step is used as substrate in the following step...
of the neurotransmitter
Neurotransmitter
Neurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to...
s serotonin
Serotonin
Serotonin or 5-hydroxytryptamine is a monoamine neurotransmitter. Biochemically derived from tryptophan, serotonin is primarily found in the gastrointestinal tract, platelets, and in the central nervous system of animals including humans...
and melatonin
Melatonin
Melatonin , also known chemically as N-acetyl-5-methoxytryptamine, is a naturally occurring compound found in animals, plants, and microbes...
from tryptophan
Tryptophan
Tryptophan is one of the 20 standard amino acids, as well as an essential amino acid in the human diet. It is encoded in the standard genetic code as the codon UGG...
.
5-HTP is sold over-the-counter in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
and Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
as a dietary supplement
Dietary supplement
A dietary supplement, also known as food supplement or nutritional supplement, is a preparation intended to supplement the diet and provide nutrients, such as vitamins, minerals, fiber, fatty acids, or amino acids, that may be missing or may not be consumed in sufficient quantities in a person's diet...
for use as an antidepressant
Antidepressant
An antidepressant is a psychiatric medication used to alleviate mood disorders, such as major depression and dysthymia and anxiety disorders such as social anxiety disorder. According to Gelder, Mayou &*Geddes people with a depressive illness will experience a therapeutic effect to their mood;...
, appetite suppressant, and sleep aid, and is also marketed in many Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
an countries for the indication of major depression under trade names like Cincofarm, Levothym, Levotonine, Oxyfan, Telesol, Tript-OH, and Triptum. Several double-blind
Double-blind
A blind or blinded experiment is a scientific experiment where some of the people involved are prevented from knowing certain information that might lead to conscious or subconscious bias on their part, invalidating the results....
placebo
Placebo
A placebo is a simulated or otherwise medically ineffectual treatment for a disease or other medical condition intended to deceive the recipient...
-controlled clinical trial
Clinical trial
Clinical trials are a set of procedures in medical research and drug development that are conducted to allow safety and efficacy data to be collected for health interventions...
s have demonstrated the effectiveness of 5-HTP in the treatment of depression, though a lack of high quality studies has been noted.
Metabolism
5-Hydroxytryptophan is decarboxylatedDecarboxylation
Decarboxylation is a chemical reaction that releases carbon dioxide . Usually, decarboxylation refers to a reaction of carboxylic acids, removing a carbon atom from a carbon chain. The reverse process, which is the first chemical step in photosynthesis, is called carbonation, the addition of CO2 to...
to serotonin
Serotonin
Serotonin or 5-hydroxytryptamine is a monoamine neurotransmitter. Biochemically derived from tryptophan, serotonin is primarily found in the gastrointestinal tract, platelets, and in the central nervous system of animals including humans...
(5-hydroxytryptamine or 5-HT) by the enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
aromatic-L-amino-acid decarboxylase with the help of vitamin B6
Vitamin B6
Vitamin B6 is a water-soluble vitamin and is part of the vitamin B complex group. Several forms of the vitamin are known, but pyridoxal phosphate is the active form and is a cofactor in many reactions of amino acid metabolism, including transamination, deamination, and decarboxylation...
. This reaction occurs both in nervous tissue and in the liver. 5-HTP crosses the blood-brain barrier
Blood-brain barrier
The blood–brain barrier is a separation of circulating blood and the brain extracellular fluid in the central nervous system . It occurs along all capillaries and consists of tight junctions around the capillaries that do not exist in normal circulation. Endothelial cells restrict the diffusion...
, while 5-HT does not. Excess 5-HTP, especially when administered with Vitamin B6
Vitamin B6
Vitamin B6 is a water-soluble vitamin and is part of the vitamin B complex group. Several forms of the vitamin are known, but pyridoxal phosphate is the active form and is a cofactor in many reactions of amino acid metabolism, including transamination, deamination, and decarboxylation...
, is thought to be metabolized and excreted.
Pharmacology
The psychoactive action of 5-HTP is derived from its effect on the production of serotonin in central nervous systemCentral nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
tissue. More specifically, 5-HTP increases the production of serotonin. Thus, it has been used to treat conditions such as depression, for which the lack of serotonin is thought to be a contributing factor.
Carbidopa
Carbidopa is a drug given to people with Parkinson's disease in order to inhibit peripheral metabolism of levodopa.- Pharmacology :...
greatly increases plasma
Blood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
5-HTP levels. However, several studies have reported that 5-HTP is effective even without a peripheral decarboxylase inhibitor (e.g. carbidopa).
Other studies have indicated the risk of a scleroderma
Scleroderma
Systemic sclerosis or systemic scleroderma is a systemic autoimmune disease or systemic connective tissue disease that is a subtype of scleroderma.-Skin symptoms:...
-like condition resulting from the combination of 5-HTP and carbidopa.
Dietary sources
Though 5-HTP is found in food only in insignificant quantities, it is a chemical involved intermediately in the metabolism of tryptophan, an amino acid found in turkey, milk, potatoes, pumpkin, and various greens. See also the section Dietary sources of the article on L-tryptophan.Therapeutic use
5-HTP is sold over-the-counter in the United StatesUnited States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, and Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
as a dietary supplement
Dietary supplement
A dietary supplement, also known as food supplement or nutritional supplement, is a preparation intended to supplement the diet and provide nutrients, such as vitamins, minerals, fiber, fatty acids, or amino acids, that may be missing or may not be consumed in sufficient quantities in a person's diet...
for use as an antidepressant
Antidepressant
An antidepressant is a psychiatric medication used to alleviate mood disorders, such as major depression and dysthymia and anxiety disorders such as social anxiety disorder. According to Gelder, Mayou &*Geddes people with a depressive illness will experience a therapeutic effect to their mood;...
, appetite suppressant, and sleep aid. 5-HTP in supplement form is typically sold in 50 mg or 100 mg gelatin
Gelatin
Gelatin is a translucent, colorless, brittle , flavorless solid substance, derived from the collagen inside animals' skin and bones. It is commonly used as a gelling agent in food, pharmaceuticals, photography, and cosmetic manufacturing. Substances containing gelatin or functioning in a similar...
or vegetarian capsules. It is usually sourced from the seeds of Griffonia simplicifolia
Griffonia simplicifolia
Griffonia simplicifolia is a woody climbing shrub native to West Africa and Central Africa. It grows to about 3 m, and bears greenish flowers followed by black pods.-Chemical constituents:...
.
5-HTP has been studied and shown to be of benefit in the following conditions: primary fibromyalgia
Fibromyalgia
Fibromyalgia is a medical disorder characterized by chronic widespread pain and allodynia, a heightened and painful response to pressure. It is an example of a diagnosis of exclusion...
syndrome, Friedreich's ataxia
Friedreich's ataxia
Friedreich's ataxia is an inherited disease that causes progressive damage to the nervous system, resulting in symptoms ranging from gait disturbance to speech problems; it can also lead to heart disease and diabetes....
, depression, anxiety, binge eating
Binge eating
Binge eating is a pattern of disordered eating which consists of episodes of uncontrollable eating. It is sometimes as a symptom of binge eating disorder. During such binges, a person rapidly consumes an excessive amount of food...
associated with obesity, and insomnia. There is no statistically significant difference between 5-HTP and placebo in treating chronic headaches (primary or otherwise).
A 2001 meta-analysis found that of 108 studies on 5-HTP published between 1966 and 2000, only two met the authors' quality standards for inclusion. The two studies that were deemed of sufficient quality did not deal with 5-HTP exclusively, instead combining results for 5-HTP and tryptophan
Tryptophan
Tryptophan is one of the 20 standard amino acids, as well as an essential amino acid in the human diet. It is encoded in the standard genetic code as the codon UGG...
, so the results may not be completely applicable for 5-HTP alone. While the combined analysis of the two 5-HTP and tryptophan studies showed significant effectiveness over placebo in treating depression, the authors state that overall "the evidence was of insufficient quality to be conclusive". They also state that "because alternative antidepressants exist which have been proven to be effective and safe, the clinical usefulness of 5-HTP and tryptophan is limited at present".
Possible risks or side effects
Because 5-HTP has not been thoroughly studied in a clinical setting, possible side effects and interactions with other drugs are not well known.Administered serotonin has been shown to increase the risk of heart valve disease in animals. 5-HTP has not been subjected to this test. 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 a false positive test in tests looking for carcinoid syndrome
Carcinoid syndrome
Carcinoid syndrome refers to the array of symptoms that occur secondary to carcinoid tumors. The syndrome includes flushing and diarrhea, and, less frequently, heart failure and bronchoconstriction...
.
5-HTP can cause hypertension
Hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...
by increasing plasma renin activity, when not co-administered with a peripheral
Peripheral nervous system
The peripheral nervous system consists of the nerves and ganglia outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system to the limbs and organs. Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood–brain...
aromatic L-amino acid decarboxylase
Aromatic L-amino acid decarboxylase
Aromatic L-amino acid decarboxylase is a lyase enzyme.-Reactions:It catalyzes several different decarboxylation reactions:* L-DOPA to dopamine - a neurotransmitter* 5-HTP to serotonin - also a neurotransmitter...
inhibitor
Enzyme inhibitor
An enzyme inhibitor is a molecule that binds to enzymes and decreases their activity. Since blocking an enzyme's activity can kill a pathogen or correct a metabolic imbalance, many drugs are enzyme inhibitors. They are also used as herbicides and pesticides...
, such as carbidopa
Carbidopa
Carbidopa is a drug given to people with Parkinson's disease in order to inhibit peripheral metabolism of levodopa.- Pharmacology :...
or benserazide
Benserazide
Benserazide is a peripherally-acting aromatic L-amino acid decarboxylase or DOPA decarboxylase inhibitor, which is unable to cross the blood-brain barrier.- Indications :...
.
Direct and indirect evidence for possible yet unproven risks and side effects associated with 5-HTP when overdosed:
- Heart valve damage or disease (cardiac fibrosisCardiac fibrosisCardiac fibrosis refers to an abnormal thickening of the heart valves due to inappropriate proliferation of cardiac fibroblasts.Fibrocyte cells normally secrete collagen, and function to provide structural support for the heart...
). - When combined with MAOIs or SSRIs, 5-HTP can cause acute serotonin syndromeSerotonin syndromeSerotonin syndrome is a potentially life-threatening adverse drug reaction that may occur following therapeutic drug use, inadvertent interactions between drugs, overdose of particular drugs, or the recreational use of certain drugs...
. - When combined with carbidopaCarbidopaCarbidopa is a drug given to people with Parkinson's disease in order to inhibit peripheral metabolism of levodopa.- Pharmacology :...
(as a treatment for symptoms of Parkinson's diseaseParkinson's diseaseParkinson's disease is a degenerative disorder of the central nervous system...
), 5-HTP causes nausea and vomiting; however this can be alleviated via administration of granisetronGranisetronGranisetron is a serotonin 5-HT3 receptor antagonist used as an antiemetic to treat nausea and vomiting following chemotherapy. Its main effect is to reduce the activity of the vagus nerve, which is a nerve that activates the vomiting center in the medulla oblongata. It does not have much effect...
. As mentioned above under pharmacology, cases of scleroderma-like illness have been reported in patients using carbidopa and 5-HTP.
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 caused by a contaminant in early 5-HTP supplements, before the introduction of the current Good Manufacturing Practices by the United States FDA in 2007. Many countries now employ similar regulation..
Further reading
- article at Psychology TodayPsychology TodayPsychology Today is a bi-monthly magazine published in the United States. It is a psychology-based magazine about relationships, health, and related topics written for a mass audience of non-psychologists. Psychology Today was founded in 1967 and features articles on such topics as love,...
- 5-Hydroxytryptophan (5-HTP) Supplement Information at University of MarylandUniversity of Maryland, BaltimoreUniversity of Maryland, Baltimore, was founded in 1807. It comprises some of the oldest professional schools in the nation and world. It is the original campus of the University System of Maryland. Located on 60 acres in downtown Baltimore, Maryland, it is part of the University System of Maryland...
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