Pyridoxine
Encyclopedia
Pyridoxine is one of the compounds that can be called 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...

, along with pyridoxal
Pyridoxal
Pyridoxal is one of the three natural forms of vitamin B6, along with pyridoxamine and pyridoxine . All of these forms are converted in the human body into a single biologically active form, pyridoxal 5-phosphate. All three forms of vitamin B6 are heterocyclic organic compounds...

 and pyridoxamine
Pyridoxamine
Pyridoxamine is a vitamer in the vitamin B6 family, which includes pyridoxal and pyridoxine. Pyridoxamine is converted to the biologically active form of vitamin B6, pyridoxal 5-phosphate, via the vitamin B6 salvage pathway. Vitamin B6 acts as an enzyme cofactor in a variety of metabolic processes...

. It differs from pyridoxamine
Pyridoxamine
Pyridoxamine is a vitamer in the vitamin B6 family, which includes pyridoxal and pyridoxine. Pyridoxamine is converted to the biologically active form of vitamin B6, pyridoxal 5-phosphate, via the vitamin B6 salvage pathway. Vitamin B6 acts as an enzyme cofactor in a variety of metabolic processes...

 by the substituent at the '4' position. It is often used as 'pyridoxine hydrochloride'.

Chemistry

It is based on a pyridine
Pyridine
Pyridine is a basic heterocyclic organic compound with the chemical formula C5H5N. It is structurally related to benzene, with one C-H group replaced by a nitrogen atom...

 ring, with hydroxyl
Hydroxyl
A hydroxyl is a chemical group containing an oxygen atom covalently bonded with a hydrogen atom. In inorganic chemistry, the hydroxyl group is known as the hydroxide ion, and scientists and reference works generally use these different terms though they refer to the same chemical structure in...

, methyl, and hydroxymethyl substituent
Substituent
In organic chemistry and biochemistry, a substituent is an atom or group of atoms substituted in place of a hydrogen atom on the parent chain of a hydrocarbon...

s. It is converted to the biologically active form pyridoxal 5-phosphate.

Function in the body

Pyridoxine assists in the balancing of sodium and potassium as well as promoting red blood cell production. It is linked to cardiovascular health by decreasing the formation of homocysteine
Homocysteine
Homocysteine is a non-protein amino acid with the formula HSCH2CH2CHCO2H. It is a homologue of the amino acid cysteine, differing by an additional methylene group. It is biosynthesized from methionine by the removal of its terminal Cε methyl group...

. Pyridoxine may help balance hormonal changes in women and aid the immune system. Lack of pyridoxine may cause anemia, nerve damage, seizures, skin problems, and sores in the mouth.

It is required for the production of the monoamine 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...

, dopamine
Dopamine
Dopamine is a catecholamine neurotransmitter present in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this substituted phenethylamine functions as a neurotransmitter, activating the five known types of dopamine receptors—D1, D2, D3, D4, and D5—and their...

, norepinephrine
Norepinephrine
Norepinephrine is the US name for noradrenaline , a catecholamine with multiple roles including as a hormone and a neurotransmitter...

 and epinephrine
Epinephrine
Epinephrine is a hormone and a neurotransmitter. It increases heart rate, constricts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. In chemical terms, adrenaline is one of a group of monoamines called the catecholamines...

, as it is the precursor to pyridoxal phosphate: cofactor for the enzyme aromatic 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...

. This enzyme is responsible for converting the precursors 5-hydroxytryptophan
5-Hydroxytryptophan
5-Hydroxytryptophan , also known as oxitriptan , is a naturally occurring amino acid and chemical precursor as well as metabolic intermediate in the biosynthesis of the neurotransmitters serotonin and melatonin from tryptophan....

 (5-HTP) into 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 levodopa
Levodopa
L-DOPA is a chemical that is made and used as part of the normal biology of some animals and plants. Some animals including humans make it via biosynthesis from the amino acid L-tyrosine. L-DOPA is the precursor to the neurotransmitters dopamine, norepinephrine , and epinephrine collectively...

 (L-DOPA) into dopamine
Dopamine
Dopamine is a catecholamine neurotransmitter present in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this substituted phenethylamine functions as a neurotransmitter, activating the five known types of dopamine receptors—D1, D2, D3, D4, and D5—and their...

, noradrenaline and adrenaline. As such it has been implicated in the treatment of depression
Clinical depression
Major depressive disorder is a mental disorder characterized by an all-encompassing low mood accompanied by low self-esteem, and by loss of interest or pleasure in normally enjoyable activities...

 and anxiety
Anxiety
Anxiety is a psychological and physiological state characterized by somatic, emotional, cognitive, and behavioral components. The root meaning of the word anxiety is 'to vex or trouble'; in either presence or absence of psychological stress, anxiety can create feelings of fear, worry, uneasiness,...

.

Very good sources of pyridoxine are grains, nuts and dragon fruit from South East Asia.

Medicinal uses

Pyridoxine is given to patients taking Isoniazid (INH)
Isoniazid
Isoniazid , also known as isonicotinylhydrazine , is an organic compound that is the first-line antituberculosis medication in prevention and treatment. It was first discovered in 1912, and later in 1951 it was found to be effective against tuberculosis by inhibiting its mycolic acid...

 to combat the toxic side effects of the drug. It is given 10–50 mg/day to patients on to prevent peripheral neuropathy
Peripheral neuropathy
Peripheral neuropathy is the term for damage to nerves of the peripheral nervous system, which may be caused either by diseases of or trauma to the nerve or the side-effects of systemic illness....

 and CNS
Central 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...

 effects that are associated with the use of INH.

It is also essential for patients with extremely rare pyridoxine-dependent epilepsy
Pyridoxine-dependent epilepsy
Pyridoxine-dependent epilepsy or pyridoxine-dependent seizure is an extremely rare disorder characterised by intractable seizures in newborn children that require lifelong B6 supplementation to treat. The disorder was first recognized in the 1950, with the first description provided by Hunt et...

, thought to be caused by mutations in the ALDH7A1
ALDH7A1
Aldehyde dehydrogenase 7 family, member A1 also known as ALDH7A1 or antiquitin is an enzyme that in humans is encoded by the ALDH7A1 gene.-Function:...

gene.

Vitamin B6 can be compounded into a variety of different dosage forms. It can be used orally as a tablet, capsule, or solution. It can also be used as a nasal spray or for injection when in its solution form.

Vitamin B6 is usually safe, at regular intakes up to 200 mg per day in adults. However, vitamin B6 can cause neurological disorders, such as loss of sensation in legs and imbalance, when taken in high doses (200 mg or more per day - 10,000% of US RDA) over a long period of time. Vitamin B6 toxicity can damage sensory nerves, leading to numbness in the hands and feet as well as difficulty walking. Symptoms of a pyridoxine overdose may include poor coordination, staggering, numbness, decreased sensation to touch, temperature, and vibration, and tiredness for up to six months.

A contradictory publication on pyridoxine toxicity reported that over a 6 month period or longer, 21% of women taking doses of less than 50 mg daily experienced neurological toxicity. The doses below 50 mg were not reported.

Based on the contradictory results of the two references cited above, some caution taking this vitamin at high doses and/or advise consulting with a physician or nutritional expert.
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