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INTRODUCTION

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pyridoxine (peer-i-dox-een)

Beesix, Doxine, Nestrex, Pyri, Rodex, Vitabee 6

OTHER NAMES:

Viatmin B6

Classification

Therapeutic: vitamins

Pharmacologic: water-soluble vitamins

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Indications
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Treatment and prevention of pyridoxine deficiency (may be associated with poor nutritional status or chronic debilitating illnesses). Treatment of pyridoxine-dependent seizures in infants. Treatment and prevention of neuropathy, which may develop from isoniazid, penicillamine, or hydralazine therapy. Management of isoniazid overdose >10 g.

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Action
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Required for amino acid, carbohydrate, and lipid metabolism. Used in the transport of amino acids, formation of neurotransmitters, and synthesis of heme. Therapeutic Effects: Prevention of pyridoxine deficiency. Prevention or reversal of neuropathy associated with hydralazine, penicillamine, or isoniazid therapy.

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Adverse Reactions/Side Effects
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Adverse reactions listed are seen with excessive doses only
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Neuro: sensory neuropathy, paresthesia. Misc: pyridoxine-dependency syndrome.

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PHYSICAL THERAPY IMPLICATIONS

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Examination and Evaluation
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  • Be alert for signs of sensory neuropathy and paresthesias (numbness, tingling). Establish baseline electroneuromyographic values using EMG and nerve conduction at the beginning of drug treatment whenever possible, and reexamine these values periodically to document changes in peripheral nerve function.

  • In infants receiving large doses, watch for signs of pyridoxine-dependency syndrome. Signs include CNS excitability (irritability, aggravated startle response, seizures) and GI distress (distension, vomiting, diarrhea). Notify physician or nursing staff if these signs occur.

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Patient/Client-Related Instruction
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  • Encourage patient to consult with a nutritionist for dietary sources of pyroxidine and other vitamins. Explain that the best source of vitamins is a well-balanced diet with foods from the four basic food groups.

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Pharmacokinetics
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Absorption: Well absorbed from the GI tract.

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Distribution: Stored in liver, muscle, and brain. Crosses the placenta and enters breast milk.

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Metabolism and Excretion: Converted in RBCs to pyridoxal phosphate and another active metabolite. Amounts in excess of requirements are excreted unchanged by the kidneys.

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Half-life: 15–20 days.

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TIME/ACTION PROFILE

ROUTE ONSET PEAK DURATION
PO, IM, IV unknown unknown unknown

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Contraindications/Precautions
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Contraindicated in: Hypersensitivity to pyridoxine or any component.

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Use Cautiously in: Parkinson's disease (treatment with levodopa only); Pregnancy (chronic ingestion of large doses may produce pyridoxine-dependency syndrome in newborn).

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Interactions
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Drug-Drug: Interferes with the therapeutic response to levodopa when used without carbidopa. Requirements are increased by isoniazid, hydralazine, chloramphenicol, penicillamine, estrogens, and immunosuppressants. Decreases serum levels of phenobarbital and phenytoin.

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Route/Dosage
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Prevention of Deficiency (Recommended Daily Allowance)
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PO (Adults and Children >14 yr): 1.2–1.7 mg/day (larger doses required with cycloserine, ethionamide, hydralazine, ...

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