PYRIDOXINE HYDROCHLORIDE (VITAMIN B6)

PYRIDOXINE HYDROCHLORIDE (VITAMIN B6) (peer-i-dox'een) Classifications: vitamin; Therapeutic:vitamin b6 replacement Pregnancy Category: A (C if greater than RDA)

Availability

25 mg, 50 mg, 100 mg, 250 mg, 500 mg tablets; 100 mg/mL injection

Action

Water-soluble complex of three closely related compounds with B₆ activity. Considered essential to human nutrition, although a deficiency syndrome is not well defined. Converted in body to pyridoxal, a coenzyme that functions in protein, fat, and carbohydrate metabolism and in facilitating release of glycogen from liver and muscle. In protein metabolism, participates in many enzymatic transformations of amino acids and conversion of tryptophan to niacin and serotonin. Aids in energy transformation in brain and nerve cells, and is thought to stimulate heme production.

Therapeutic Effect

Evaluated by improvement of B₆ deficiency manifestations: Nausea, vomiting, skin lesions resembling those of riboflavin and niacin deficiency, edema, CNS symptoms, hypochromic microcytic anemia.

Uses

Prophylaxis and treatment of pyridoxine deficiency, as seen with inadequate dietary intake, drug-induced deficiency (e.g., isoniazid, oral contraceptives), and inborn errors of metabolism (vitamin B₆–dependent convulsions or anemia). Also to prevent chloramphenicol-induced optic neuritis, to treat acute toxicity caused by overdosage of cycloserine, hydralazine, isoniazid (INH); alcoholic polyneuritis; sideroblastic anemia associated with high serum iron concentration. Has been used for management of many other conditions ranging from nausea and vomiting in radiation sickness and pregnancy to suppression of postpartum lactation.

Contraindications

Pregnancy [category A (C if >RDA)].

Cautious Use

Renal impairment; neonatal prematurity with renal impairment; cardiac disease.

Route & Dosage

Dietary Deficiency Adult: PO/IM/IV 10–20 mg/d x 2–3 wk Child: PO 5–25 mg/d x 3 wk, then 1.5–2.5 mg/d Pyridoxine Deficiency Syndrome Adult: PO/IM/IV Initial dose up to 600 mg/d may be required; then up to 50 mg/d Isoniazid-Induced Deficiency Adult: PO/IM/IV 100 mg/d x 3 wk, then 30 mg/d Child: PO 10–50 mg/d x 3 wk, then 1–2 mg/kg/d Pyridoxine-Dependent Seizures Neonate/Infant: PO/IM/IV 50–100 mg/d

Administration

Oral

• Ensure that sustained release and enteric forms are not chewed or crushed. Must be swallowed whole.

Intramuscular

• Give deep IM into a large muscle.

Intravenous PREPARE: Direct: Give undiluted.  Continuous: May be added to most standard IV solutions.   ADMINISTER: Direct: Give at a rate of 50 mg or fraction thereof over 60 seconds.  Continuous: Give according to ordered rate for infusion.

• Store at 15°–30° C (59°–86° F) in tight, light-resistant containers. Avoid freezing.

Adverse Effects (≥1%)

Body as a Whole: Paresthesias, slight flushing or feeling of warmth, temporary burning or stinging pain in injection site. CNS: Somnolence seizures (particularly following large parenteral doses). Metabolic: Low folic acid levels.

Interactions

Drug: Isoniazid, cycloserine, penicillamine, hydralazine and oral contraceptives, may increase pyridoxine requirements; may reverse or antagonize therapeutic effects of levodopa.

Pharmacokinetics

Absorption: Readily from GI tract. Distribution: Stored in liver; crosses placenta. Metabolism: In liver. Elimination: In urine.

Nursing Implications

Assessment & Drug Effects

• Monitor neurological status to determine therapeutic effect in deficiency states.
• Record a complete dietary history so poor eating habits can be identified and corrected (a single vitamin deficiency is rare; patient can be expected to have multiple vitamin deficiencies).
• Lab tests: Periodic Hct and Hgb, and serum iron.

Patient & Family Education

• Learn rich dietary sources of vitamin B₆: Yeast, wheat germ, whole grain cereals, muscle and glandular meats (especially liver), legumes, green vegetables, bananas.
• Do not self-medicate with vitamin combinations (OTC) without first consulting physician.

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Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug