Pyridoxine

BRAND NAMES 

Pyridoxine, commonly referred to as vitamin B6, is marketed under several brand names and is available either as a standalone supplement or combined.

• Nestrex (Vitelle Nestrex): A commonly used U.S. brand containing pyridoxine for supplementation. 

• Vitamin B6: Pyridoxine is widely available as a generic supplement under its common name.ith other drugs, such as doxylamine, for the management of morning sickness. 

• B-Long: An Indian dietary supplement containing pyridoxine, commonly used to prevent or treat vitamin B6 deficiency. 

• Hexa-Betalin: A U.S. brand name for the hydrochloride form of vitamin B6. 

MECHANISM OF ACTION

Vitamin B6 refers to a group of three closely related compounds: pyridoxine (PN), pyridoxal (PL), and pyridoxamine (PM), along with their phosphorylated forms—pyridoxine 5′-phosphate (PNP), pyridoxal 5′-phosphate (PLP), and pyridoxamine 5′-phosphate (PMP). Although all six compounds collectively constitute vitamin B6, the term is commonly used to specifically denote pyridoxine. The biologically active form of vitamin B6, pyridoxal 5′-phosphate, functions as a vital coenzyme in numerous biochemical processes. These include amino acid and glycogen metabolism, nucleic acid synthesis, and the formation of hemoglobin, sphingomyelin, and other sphingolipids. Additionally, it plays a key role in the synthesis of important neurotransmitters such as serotonin, dopamine, norepinephrine, and gamma-aminobutyric acid (GABA). 

PHARMACOKINETICS

Absorption

B vitamins are generally well absorbed from the gastrointestinal tract, except in conditions associated with malabsorption. Pyridoxine is primarily absorbed in the jejunum, and its maximum plasma concentration (Cmax) is reached approximately 5.5 hours after administration. 

Distribution

The primary active metabolite of pyridoxine, pyridoxal 5′-phosphate, is released into the bloodstream, where it constitutes at least 60% of circulating vitamin B6. This metabolite is extensively bound to plasma proteins, mainly albumin.

Metabolism

Pyridoxine acts as a prodrug and is mainly metabolized in the liver. Its metabolism is complex, involving the formation of both primary and secondary metabolites, as well as interconversion back to pyridoxine. The principal metabolite of pyridoxine is 4-pyridoxic acid. 

Elimination

The primary metabolite of pyridoxine, 4-pyridoxic acid, is biologically inactive and is eliminated from the body through urine. 

PHARMACODYNAMICS

Vitamin B6 (pyridoxine) is a water-soluble vitamin used to prevent and treat deficiency and isoniazid-induced peripheral neuropathy. It may help lower blood pressure, improve cholesterol levels, inhibit platelet aggregation, and protect vascular endothelial cells. Deficiency of vitamin B6 can impair immune function, affecting lymphocyte development, antibody production, and cytokine (IL-2) levels. 

ADMINISTRATION

Pyridoxine (Vitamin B6) can be given orally, intravenously (IV), intramuscularly (IM), or subcutaneously, with the route selected based on the patient’s condition and the severity of the deficiency. It serves as an essential coenzyme in the metabolism of amino acids, carbohydrates, and fats, and sufficient levels are vital for proper nervous system function and the synthesis of neurotransmitters.

DOSAGE AND STRENGTH 

Pyridoxine (Vitamin B6) dosage depends on the patient’s age, condition, and route of administration. For preventing or treating vitamin B6 deficiency in adults, oral doses typically range from 10 to 50 mg daily, while children’s doses are calculated based on body weight. In patients taking isoniazid (INH), 10–25 mg daily is usually given to prevent peripheral neuropathy. Pyridoxine is available in various strengths, including 10 mg, 25 mg, and 50 mg tablets, as well as injectable forms for intravenous, intramuscular, or subcutaneous use, with the choice of strength and route tailored to clinical needs and severity of deficiency. 

DRUG INTERACTIONS

 Pyridoxine (Vitamin B6) may interact with several medications, affecting their efficacy or increasing the risk of side effects. Isoniazid, hydralazine, and penicillamine can cause vitamin B6 deficiency, often necessitating supplementation. Levodopa effectiveness may be reduced when taken with high doses of pyridoxine, as it can increase peripheral metabolism of the drug unless combined with a peripheral decarboxylase inhibitor.

 FOOD INTERACTIONS

Pyridoxine (Vitamin B6) is generally well absorbed from food, and no major food interactions are reported. However, excessive consumption of raw egg whites over time may reduce vitamin B6 absorption due to the protein avidin binding the vitamin. 

CONTRAINDICATIONS

Pyridoxine (Vitamin B6) is generally safe when taken at recommended dietary levels, but its use is contraindicated or requires extreme caution in several specific medical scenarios as of 2026.

SIDE EFFECTS 

• Upset stomach or nausea 

• Headache 

• Drowsiness or sleepiness 

• Slight tingling or a numbing sensation can occur in the hands or feet. Loss of appetite 

OVER DOSE

Excessive or prolonged intake of high doses may lead to sensory neuropathy, characterized by numbness, tingling, or burning sensations in the hands and feet. Other symptoms can include difficulty in coordination, unsteady gait, and muscle weakness. High doses may also cause headache, nausea, fatigue, and sensitivity to light. Symptoms usually improve after discontinuation or dose reduction, but recovery may be slow in severe cases. Medical evaluation is recommended if overdose or long-term high-dose use is suspected. 

TOXICITY

Pyridoxine (Vitamin B6) toxicity mainly leads to sensory neuropathy, causing numbness, tingling, pain, and poor coordination, typically starting in the hands and feet. It usually results from prolonged intake of very high doses (over 1000 mg/day) rather than from dietary sources. Symptoms may include impaired sensation of touch, vibration, and body position, affecting balance and walking.