Pyridoxine Hcl (pyridoxine HCl (vitamin B6))

Although pyridoxine was previously considered nontoxic even at high dosages, current evidence indicates that chronic administration of large dosages (e.g., 2 g daily) for the management of various conditions can cause severe adverse neurologic effects, and the risk to benefit of such dosages must be carefully weighed. (See Chronic Toxicity.)

Pyridoxine hydrochloride is usually administered orally; however, the drug may be given by IM, IV, or subcutaneous injection when oral administration is not feasible. In infants with seizures, pyridoxine hydrochloride should be administered by IM or IV injection.

No dosing information is available for this tab.

No dosing information is available for this tab.

Pyridoxine hydrochloride reverses the therapeutic effects of levodopa by accelerating peripheral metabolism of levodopa. Concomitant administration of carbidopa with levodopa prevents the reversal by pyridoxine of levodopa's effects. Pyridoxine hydrochloride should not be administered in dosages greater than 5 mg daily to patients receiving levodopa alone.

In one study, 200 mg of pyridoxine hydrochloride daily for 1 month resulted in a 50% decrease in serum concentrations of phenobarbital and phenytoin.

Although isoniazid interferes with pyridoxine metabolism, the American Academy of Pediatrics (AAP) states that children receiving isoniazid do not need pyridoxine supplements unless they have or are likely to have nutritional deficiencies. The AAP currently recommends that children and adolescents receiving meat- and milk-deficient diets, those with nutritional deficiencies (including symptomatic children with human immunodeficiency virus (HIV) infection), infants who are breast-feeding and their mothers, and pregnant women receive pyridoxine supplements.

Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

Pyridoxine/Altretamine

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: The mechanism by which pyridoxine adversely affects response duration while coadministering altretamine is not known at this time and requires further investigation.

CLINICAL EFFECTS: The coadministration of oral pyridoxine with chemotherapy regimens consisting of oral altretamine adversely affected response duration.(1,2)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Although pyridoxine administration significantly reduces the neurotoxicity associated with altretamine, it should not be administered with altretamine due to its adverse effect on response duration.(1,2)

DISCUSSION: In a study, 248 patients with Stages III-IV ovarian epithelial cancer were randomized to one of four cisplatin and altretamine regimens. In each regimen, oral altretamine (200 mg/m2 daily) was administered on days 8-21. In addition, intravenous cisplatin was administered on day 1 (37.5 mg/m2, regimens A and B, or 75 mg/m2, regimens C and D). Oral pyridoxine (300 mg/m2 daily, days 1-21) was added to regimens B and D. While pyridoxine did decrease neurologic toxicity and had no effect on response, pyridoxine was found to adversely affect response duration in all patients. This effect was the greatest in previously untreated patients. In addition, pyridoxine had a slight negative effect on failure-free survival in previously untreated patients.(1)

There are no severe interactions for this drug.

Moderate Interaction: Assess the risk to the patient and take action as needed.

Pyridoxine/Levodopa

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Pyridoxine increases levodopa metabolism, decreasing the amount of levodopa available to the central nervous system.

CLINICAL EFFECTS: The pharmacologic effects of levodopa may be decreased.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Avoid pyridoxine in patients receiving levodopa alone; however, the interaction can be minimized by giving levodopa with a peripheral decarboxylase inhibitor (e.g. carbidopa, benserazide). Treatment with combination carbidopa-levodopa may contribute to reduced vitamin B6 levels. Higher doses of carbidopa-levodopa may increase the risk of vitamin B6 deficiency. Seizures associated with vitamin B6 deficiency have been reported in the postmarketing setting. In patients taking combination therapy with carbidopa/levodopa, evaluate vitamin B6 levels periodically while on treatment or if symptoms associated with vitamin B6 deficiency are identified. Supplement with vitamin B6 as necessary.

DISCUSSION: In patients with Parkinson's disease, as little as 10 mg of pyridoxine may reverse the clinical benefits as well as the adverse effects of levodopa. Coadministration of levodopa with either carbidopa or benserazide has minimized the effects of this interaction.

There is no enhanced messaging for this drug.

There are no contraindication contraindications for this drug.

There are no severe contraindications for this drug.

• No disease contraindications

There is no enhanced messaging for this drug.

Rare or Very Rare

• Peripheral sensory neuropathy

Rare or Very Rare

• Drowsy
• Headache disorder
• Nausea
• Paresthesia

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