PYRIDOXINE HYDROCHLORIDE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PYRIDOXINE HYDROCHLORIDE (PYRIDOXINE HYDROCHLORIDE).
Pyridoxine hydrochloride is a water-soluble vitamin that serves as a cofactor for over 100 enzymes involved in amino acid, carbohydrate, and lipid metabolism. It is converted to pyridoxal phosphate, which participates in transamination, deamination, decarboxylation, and other reactions.
| Metabolism | Pyridoxine is metabolized in the liver via oxidation to 4-pyridoxic acid, which is excreted in urine. Minor pathways include conversion to pyridoxal phosphate and other metabolites. |
| Excretion | Renal excretion of 4-pyridoxic acid and other metabolites accounts for >90% of elimination; <2% excreted unchanged in urine. |
| Half-life | Terminal half-life is 15–20 days for pyridoxine and its phosphate esters due to extensive tissue binding and slow release; free pyridoxine half-life 1–2 hours. |
| Protein binding | ~60% bound to albumin, primarily for pyridoxal phosphate. |
| Volume of Distribution | 0.6–1.0 L/kg; reflects extensive tissue distribution and storage, particularly in liver, muscle, and brain. |
| Bioavailability | Oral: 80–90% (dose-dependent, saturable absorption). |
| Onset of Action | Oral: 30–60 minutes for symptomatic improvement in deficiency states; IV/IM: within 2–5 minutes for acute toxic seizures. |
| Duration of Action | Oral: 8–12 hours for single dose effects; with regular supplementation, effects last weeks to months due to tissue storage. |
25-50 mg orally daily for dietary supplementation; 100-200 mg orally daily for vitamin B6 deficiency; 100 mg orally once daily for prophylaxis of neuropathy (e.g., isoniazid therapy); 30-600 mg orally daily in divided doses for pyridoxine-dependent seizures.
| Dosage form | INJECTABLE |
| Renal impairment | No dosage adjustment required for GFR >15 mL/min. For GFR <15 mL/min (ESRD), maximum dose should not exceed 100 mg/day due to risk of neuropathy. |
| Liver impairment | No dosage adjustment required for Child-Pugh Class A or B. For Class C (severe hepatic impairment), consider reducing dose by 50% due to impaired conversion to active form. |
| Pediatric use | Dietary supplementation: 0.5-1 mg/kg/day orally. Deficiency: 5-25 mg orally daily for 3 weeks. Pyridoxine-dependent seizures: 10-25 mg/kg/day orally, titrated to response; maximum 100 mg/day. |
| Geriatric use | No specific dose adjustment required; however, monitor for peripheral neuropathy with prolonged high-dose use (>200 mg/day). Lower initial doses may be considered due to age-related renal decline. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PYRIDOXINE HYDROCHLORIDE (PYRIDOXINE HYDROCHLORIDE).
| Breastfeeding | Pyridoxine is excreted into breast milk in concentrations sufficient to meet infant requirements. The M/P ratio is approximately 0.5–1.0. No adverse effects reported in breastfed infants. Safe for use during lactation at recommended doses (up to 2 mg/day in infants). |
| Teratogenic Risk | Pyridoxine hydrochloride is FDA pregnancy category A. No evidence of teratogenicity in first trimester. Animal studies show no fetal harm. Sufficient data in pregnant women indicate no malformative or fetotoxic risk. Safe for hyperemesis gravidarum at recommended doses. |
■ FDA Black Box Warning
None.
| Serious Effects |
Hypersensitivity to pyridoxine or any component of the formulation. No absolute contraindications documented; relative caution in patients with impaired renal function due to potential accumulation of metabolites.
| Precautions | Use with caution in patients with known hypersensitivity to pyridoxine. Large doses (≥200 mg/day) for prolonged periods may cause peripheral neuropathy. Avoid abrupt discontinuation in patients with pyridoxine dependency. Monitor for neurotoxicity at high doses. |
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| Fetal Monitoring | No specific monitoring required. Assess maternal symptoms of vitamin B6 deficiency (e.g., dermatitis, glossitis, neuropathy). Monitor for possible toxicity with high doses (e.g., sensory neuropathy). |
| Fertility Effects | No adverse effects on fertility. Pyridoxine is essential for reproductive function. Deficiency may cause infertility, corrected by supplementation. |