Class: Vitamin, water-soluble
- Tablets 10 mg
- Tablets 25 mg
- Tablets 50 mg
- Tablets 100 mg
- Tablets 200 mg
- Tablets 250 mg
- Tablets, extended-release 200 mg
- Capsules 500 mg
- Solution 200 mg per 5 mL
- Tablets 500 mg
- Capsules 150 mg
- Injection 100 mg/mL
Mechanism of Action
Vitamin B 6 functions as coenzyme in amino acid, carbohydrate, and lipid metabolism.
Absorbed by passive diffusion in the jejunum and to a lesser extent in the ileum.
Primarily stored in the liver, lesser amount in the muscle and brain. Not protein bound.
Metabolized in the liver and converted to 4-pyridoxic acid metabolite.
Excreted mostly as 4-pyridoxic acid in the urine. The t ½ is 15 to 20 days.
Indications and Usage
Pyridoxine deficiency, including inadequate diet, drug-induced causes (eg, isoniazid, hydralazine, oral contraceptives) or inborn errors of metabolism. Parenteral use is indicated when oral therapy is not feasible.
Treatment of hydrazine poisoning, PMS, hyperoxaluria type I, nausea and vomiting in pregnancy, sideroblastic anemia associated with high serum iron, carpal tunnel syndrome, tardive dyskinesia.
Dosage and AdministrationDietary Deficiency
PO / IM / IV 10 to 20 mg/day for 3 wk.Drug-Induced Deficiency Anemia or Neuritis
PO / IM / IV 100 to 200 mg/day for 3 wk; follow with 25 to 100 mg/day.Neuropathy
PO / IM / IV 50 to 200 mg/day.Vitamin B 6 Dependency Syndrome
PO / IM / IV 600 mg, followed by 30 mg/day for life. Dependency has been noted in adults administered 200 mg/day.Pyridoxine-dependent infants
IM / IV 10 to 100 mg, followed by 2 to 100 mg/day.Metabolic Disorders
PO / IM / IV 100 to 500 mg/day.Isoniazid Poisoning
Adults and children
IV 4 g IV followed by 1 g IM every 30 min until pyridoxine dose equal to isoniazid dose has been given.
- Instruct patient to swallow enteric-coated preparation whole and not to break, crush or chew.
- When giving via IM route, rotate sites.
- IV preparation may be given undiluted or added to standard compatible IV solutions.
Store all forms of drug at room temperature in tightly closed, light-resistant containers. Avoid freezing injection.
Drug InteractionsCycloserine, isoniazid, hydralazine, oral contraceptives, penicillamine
Increased need for pyridoxine.Levodopa
Decreased effect of levodopa. (Interaction does not occur with levodopa/carbidopa in combination with pyridoxine.)Phenytoin
Phenytoin serum levels may be decreased.
Incompatible with alkaline solutions, iron salts and oxidizing agents (parenteral).
Laboratory Test Interactions
May result in false-positive urobilinogen in the spot test using Ehrlich reagent.
Neuropathy; unstable gait; drowsiness; somnolence.
Numbness of feet; decreased sensation to touch, temperature or vibration; paresthesia; low serum folic acid levels; burning/stinging at IM injection site; photoallergic reaction; ataxia.
Category A . ( Category C in doses that exceed the RDA.)
Excreted in breast milk; may inhibit lactation.
Safety and efficacy not established in doses exceeding nutritional requirements.
Ataxia, sensory neuropathy.
- Emphasize importance of complying with prescribed dietary recommendations.
- Teach patient about foods high in B 6 (whole grain cereals, meat [eg, liver], potatoes, green vegetables, legumes [eg, lima beans], yeast and bananas).
- If patient is self-medicating with vitamin supplements, caution that megadosing may cause side effects such as unsteady gait, impaired hand coordination and numbness of feet.