VER VITAMINA B6

 

Description: Pyridoxine, or vitamin B6, is a naturally occurring, water-soluble vitamin found in food such as cereal grains, legumes, vegetables, liver, meat, and eggs. Pyridoxine is used to treat and prevent vitamin B6 deficiency; to prevent or treat toxicity from isoniazid, cycloserine, or hydralazine; and to treat sideroblastic anemia associated with elevated serum iron levels. It also has been used in pyridoxine-dependent neonates to treat seizures that are unresponsive to conventional therapy and in patients with metabolic disorders such as xanthurenic aciduria, primary hyperoxaluria, primary cystathioninuria, and primary homocystinuria. Pyridoxine hydrochloride has been commercially available since approval by the FDA in 1940. Mechanism of Action: Vitamin B6 is composed of pyridoxine, pyridoxal, and pyridoxamine, and food usually contains all three forms. Pyridoxine is converted in erythrocytes to its active moiety, pyridoxal phosphate (requiring riboflavin for the conversion), while pyridoxamine is converted into pyridoxamine phosphate. These active forms act as coenzymes for no fewer than 60 metabolic processes including the metabolism of fat, protein, and carbohydrate. Their role in protein metabolism includes decarboxylation of amino acids, conversion of tryptophan to niacin or serotonin, deamination, and transamination of amino acids. In carbohydrate metabolism, it is necessary for the conversion of glycogen to glucose-1-phosphate. Pyridoxine is essential for synthesis of gamma aminobutyric acid (GABA) in the CNS and synthesis of heme. Pharmacokinetics: Pyridoxine is administered orally and by intramuscular or intravenous injection. Absorption is rapid following oral administration. The extent of absorption is decreased following gastric resection or in patients with malabsorption syndromes. Vitamin B6 is stored in the liver, with small amounts in the brain and muscles. The total body storage for adults is between 16—27 mg. Pyridoxal crosses the placenta, with fetal concentrations five times that of maternal plasma concentrations. Pyridoxal and pyridoxal phosphate are the primary forms of vitamin B6 in the blood. Pyridoxal phosphate is 100% protein-bound. The half-life of pyridoxine is 15—20 days. Conversion of pyridoxine to pyridoxal phosphate, and pyridoxamine to pyridoxamine phosphate takes place in erythrocytes. Pyridoxine is also phosphorylated in the liver. Pyridoxal is oxidized in the liver to produce 4-pyridoxic acid, which is excreted in the urine.

Indications...Dosage For nutritional supplementation: •the recommended dietary allowance (RDA) of pyridoxine for nutritional supplementation in healthy individuals: Oral dosage: Adult and adolescent females during lactation: 2 mg/day PO while breast-feeding. Adult and adolescent pregnant females: 1.9 mg/day PO. Adult females >= 51 years of age: 1.5 mg/day PO. Adult males >= 51 years of age: 1.7 mg/day PO. Adults 19—50 years of age: 1.3 mg/day PO. Adolescent females 14—18 years of age: 1.2 mg/day PO. Adolsescent males 14—18 years of age: 1.3 mg/day PO. Children 9—13 years of age: 1 mg/day PO. Children 4—8 years of age: 0.6 mg/day PO. Children 1—3 years of age: 0.5 mg/day PO. Infants 6—11 months of age: 0.3 mg/day PO based on Adequate Intake (AI). RDA has not been established. Infants <= 5 months of age: 0.1 mg/day PO based on Adequate Intake (AI). RDA has not been established. •in patients receiving total parenteral nutrition (TPN): Intravenous dosage: Adults: 4 mg/day IV admixed with TPN. For the treatment of vitamin B6 deficiency states, including neuritis or seizures, that are not drug-induced: Oral dosage: Adults without neuritis: 2.5—10 mg/day PO. After the deficiency has been corrected, 2—5 mg/day may be given for several weeks. Adults with neuritis: 100—200 mg/day PO for 3 weeks, then 25—100 mg/day PO thereafter. Children without neuritis: 5—25 mg/day for 3 weeks, then 1.5—2.5 mg/day in a multivitamin product. Children with neuritis: 10—50 mg/day PO per day for 3 weeks, then 1—2 mg/day PO. Parenteral dosage: Neonates with seizures: 50—100 mg IM or IV as a single dose. Chronic treatment with 50—100 mg/day PO is often required in infants with pyridoxine-responsive seizures with no other identifiable cause. For the treatment of sideroblastic anemia: Oral dosage: Adults: 200—600 mg/day PO. Following an adequate response, 30—50 mg/day PO may be used. Children: Dosage not established. For the treatment of seizures due to acute mushroom poisoning: Intravenous dosage: Adults: 25 mg/kg IV administered over 15—30 minutes. May be repeated as necessary to a total dose of 15—20 g/day. For the treatment of cycloserine toxicity related to pyridoxine deficiency: Oral dosage: Adults: 25—100 mg/day PO for 3 weeks, followed by 2—2.5 mg PO once daily. Children: 10—50 mg/day PO. For the treatment of acute cycloserine overdose: Intravenous dosage: Adults: A dose of 300 mg/day IV has been recommended. For cycloserine toxicity prophylaxis: Oral dosage: Adults: 100—300 mg/day PO has been recommended. Children: 1—2 mg/kg/day PO. For the treatment of hydralazine toxicity related to pyridoxine deficiency: Oral dosage: Adults: 100—300 mg/day PO. Children: 10—50 mg/day PO. For hydralazine toxicity prophylaxis: Oral dosage: Adults: 100 mg PO once daily has been recommended. Children: 1—2 mg/kg/day PO. For the treatment of isoniazid toxicity (other than seizures) related to pyridoxine deficiency: Oral dosage: Adults: 100—300 mg/day PO. Children: 10—50 mg/day PO. •for the treatment of drug-induced seizures secondary to acute isoniazid overdose: Parenteral dosage: Adults: A dose of pyridoxine equal to the amount of isoniazid ingested is usually given (i.e., mg-for-mg). In general, 1—4 grams IV bolus followed by 1 gram IM every 30 minutes until the entire dose has been given. For isoniazid toxicity prophylaxis: Oral dosage: Adults: Doses of 10—75 mg/day PO have been recommended. Children: 1—2 mg/kg/day PO. Infants: 0.1—0.5 mg/day PO. If neurologic symptoms develop in pediatric patients, increase dosage as necessary. •in HIV-infected patients receiving isoniazid for primary Mycobacterium tuberculosis prophylaxis: Oral dosage: Adults and adolescents: In patients receiving isoniazid once daily, the CDC recommends pyridoxine 50 mg PO once daily. In patients receiving isoniazid twice weekly, the CDC recommends pyridoxine 50 mg PO twice weekly.[1446] For oral contraceptive toxicity prophylaxis: Oral dosage: Adult females: 25—30 mg/day PO. For penicillamine toxicity prophylaxis: Oral dosage: Adults: 10—50 mg/day PO. Children: 1—2 mg/kg/day PO. Infants: 0.1—0.5 mg/day PO. If neurologic symptoms develop in pediatric patients, increase dosage as necessary. •for treatment of acute penicillamine toxicity: Oral dosage: Adults: 25—100 mg PO once daily for 3 weeks followed by 2—2.5 mg PO once daily. Children: 10—50 mg/day PO. For the treatment of metabolic disorders including, primary cystathioninuria, primary homocystinuria, or xanthurenic aciduria: Oral dosage: Adults: 100—500 mg/day PO. Children: Dosage not established. For the treatment of primary hyperoxaluria† in combination with oral orthophosphate therapy: Oral dosage: Adults and children: In one trial, the initial dose of pyridoxine ranged 1.8—7 mg/kg/day (mean 3.4 mg/kg/day) PO with a final dose of 1—7 mg/kg/day (mean 2.9 mg/kg/day) was given in combination with oral orthophosphate therapy. Five patients or 25 patients progressed to end-stage renal disease which occurred from 7—23 years after treatment began. No patient had neuropathy or other signs of pyridoxine toxicity.[573] For the treatment of premenstrual syndrome (PMS): Oral dosage: Adults: The efficacy of pyridoxine in the treatment of PMS is unclear. Some studies have shown benefit, while others have shown none. Doses have ranged from 80—500 mg/day PO.[578] For the treatment of nausea/vomiting† during pregnancy: Oral dosage: Adults: Pyridoxine 10 mg PO three times a day was shown to decrease the number of vomiting episodes as compared to women receiving placebo. Improvement in nausea scores was also superior in the pyridoxine group relative to placebo.[973] Patients with renal impairment: Specific guidelines for dosage adjustments in renal impairment are not available; it appears that no dosage adjustments are needed. Patients with hepatic impairment: Specific guidelines for dosage adjustments in hepatic impairment are not available; it appears that no dosage adjustments are needed. †non-FDA-approved indication

 

Pyridoxine, Vitamin B6 Vitamin B{6} by Target | Nutri-Doxine™ | Pro-B Six™ | Rodexฎ

573. Milliner DS, Eickholt JT, Bergstralh EJ et al. Results of long-term treatment with orthophosphate and pyridoxine in patients with primary hyperoxaluria. N Engl J Med 1994;331:1553—8.

1446. Centers for Disease Control and Prevention. 1999 USPHS/IDSA Guidelines for the prevention of opportunistic infections in persons infected with human immunodeficiency virus. Morbid Mortal Weekly Rep 1999;48:1—66.