Vitamin B12

Brand names: Nascobal
Drug class: Antineoplastic Agents

Usage of Vitamin B12

Vitamin B12 Deficiency

Treatment of pernicious anemia and other vitamin B12 deficiency states.

Parenteral cyanocobalamin or hydroxocobalamin: Treatment of vitamin B12 deficiency due to inadequate intrinsic factor (IF) secretion; impaired intestinal absorption; or dietary deficiency associated with a vegetarian diet.

Cyanocobalamin is considered the parenteral vitamin B12 preparation of choice; hydroxocobalamin may be preferred for initial treatment.

Cyanocobalamin nasal spray: Used to maintain hematologic status in adults with pernicious anemia with no nervous system involvement who have responded to parenteral vitamin B 12 therapy. Also used as a supplement for vitamin B12 deficiency due to dietary deficiency, impaired absorption, inadequate secretion of IF, or certain other conditions.

Dietary Requirements

Adequate intake needed to prevent vitamin B12 deficiency and neurologic complications associated with vitamin B12 deficiency.

Adequate intake of vitamin B12 usually can be accomplished through consumption of foodstuffs; however, about 10–30% of geriatric individuals are unable to absorb naturally occurring vitamin B12 and should consume vitamin B12-fortified food or supplements. Inadequate intake can occur in vegetarians and their breast-fed infants. Mixed foods whose main ingredient is meat, fish, or poultry; milk; and fortified ready-to-eat cereals are the main sources of vitamin B12 in the diet of US adults and children.

Recommended Dietary Allowance (RDA) in adults based on amount needed to maintain hematologic status and normal serum vitamin B12 concentrations.

Adequate intake (AI) established for infants ≤6 months of age based on observed mean vitamin B12 intake of infants fed principally human milk; AI for infants 7–12 months of age based on AI for younger infants and data in adults.

RDA for children 1–18 years of age based on data in adults.

Metabolic Disorders

Parenteral cyanocobalamin: Management of hereditary deficiency of transcobalamin II.

Schilling Test

Parenteral cyanocobalamin and hydroxocobalamin: Used in conjunction with cyanocobalamin Co 57 in Schilling test to study vitamin B12 absorption.

Cyanide Poisoning

Hydroxocobalamin (Cyanokit): Treatment of known or suspected cyanide poisoning. Used in conjunction with airway and cardiovascular support and management of seizure activity.

Relate drugs

How to use Vitamin B12

Administration

Cyanocobalamin is administered orally, intranasally, or by IM or deep sub-Q injection.

Hydroxocobalamin is administered by IM injection or IV infusion.

Oral Administration

Oral therapy is inferior to parenteral therapy. May be used for treatment of dietary vitamin B12 deficiency in patients with normal GI absorption.

Parenteral Administration

Cyanocobalamin: Administer by IM or deep sub-Q injection. If administered sub-Q, avoid injection into the dermis or upper suBCutaneous tissue. Avoid administering IV; vitamin is rapidly excreted in urine when administered IV.

Hydroxocobalamin: Administer by IM injection (vitamin deficiency) or by IV infusion (cyanide poisoning). Avoid administering IV for vitamin deficiency.

For drug compatibility information, see Compatibility under Stability.

IV Administration for Cyanide Poisoning

Hydroxocobalamin: (Cyanokit); Administer by IV infusion.

May require a dedicated IV line. Administration through the same IV line as blood products not recommended.

Reconstitution

Reconstitute vial containing 2.5 g of hydroxocobalamin with 100 mL of 0.9% sodium chloride injection; invert or rock vial for at least 30 seconds. Do not shake vial. Lactated Ringer's injection or 5% dextrose injection can be used if 0.9% sodium chloride injection is not available. Reconstituted solution contains 25 mg/mL.

Rate of Administration

Initial 5-g dose: 15 minutes.

Second 5-g dose: 15 minutes (for patients in extremis) to 2 hours; rate depends on patient condition.

Intranasal Administration

Administer intranasally using a metered-dose pump. Administer 1 hour before or 1 hour after ingestion of hot foods or liquids.

Prior to intranasal administration, clear nasal passages. Insert the nasal adapter 1 cm into one nostril, point the tip of the adapter toward the back of the nose, hold the other nostril closed, and tilt head slightly forward, pump the drug into nostril, sniff gently during and immediately after dosing, return head to upright position, remove pump unit from nose.

Efficacy has not been established in patients with nasal congestion, allergic rhinitis, or upper respiratory tract infection; defer use until these symptoms have subsided.

Prime the pump before each use.

Dosage

Vitamin B 12 deficiency: Duration of therapy depends on cause; long-term therapy not needed when other therapeutic measures correct the underlying cause of the deficiency.

Cyanocobalamin metered-dose pump delivers 500 mcg of the drug (0.1 mL) per actuation.

Pediatric Patients

Vitamin B 12 Deficiency IM

Hydroxocobalamin: Initially, single doses of 100 mcg to total dose of 1–5 mg given over ≥2 weeks.

Hydroxocobalamin: Maintenance, 30–50 mcg every 4 weeks.

Dietary and Replacement Requirements Oral

Infants born to vegan mothers: Supplement with AI from birth because these infants' vitamin B12 stores are low and their mother’s milk may supply very small amounts of the vitamin.

Infants ≤6 months of age: Recommended AI is 0.4 mcg (0.06 mcg/kg) daily.

Infants 7–12 months of age: Recommended AI is 0.5 mcg (0.06 mcg/kg) daily.

Children 1–3 years of age: RDA is 0.9 mcg daily.

Children 4–8 years of age: RDA is 1.2 mcg daily.

Children 9–13 years of age: RDA is 1.8 mcg daily.

Children 14-18 years of age: RDA is 2.4 mcg daily.

The RDAs will not meet the needs of individuals with malabsorption syndrome.

Cyanide Poisoning† [off-label] IV

Hydroxocobalamin: 70 mg/kg has been used.

Adults

Vitamin B 12 Deficiency IM or Sub-Q

Cyanocobalamin: Initially, 100 mcg daily for 6–7 days. If clinical manifestations improve and reticulocyte response observed, administer 100 mcg every other day for 7 doses and then 100 mcg every 3–4 days for 2–3 weeks.

Cyanocobalamin: Maintenance, 100 mcg every month.

IM

Hydroxocobalamin: Initially, 30 mcg daily for 5–10 days.

Hydroxocobalamin: Maintenance, 100–200 mcg every month.

Intranasal

Maintenance, 500 mcg (one actuation) once weekly. Increase dose in patients who experience a decline in serum vitamin B12 concentrations after 1 month of therapy.

Dietary and Replacement Requirements Oral

Men and women ≥19 years of age: RDA is 2.4 mcg daily.

Adults ≥51 years of age should obtain most of their vitamin B12 from fortified food or a vitamin B12 supplement.

The RDAs will not meet the needs of individuals with malabsorption syndrome.

Cyanide Poisoning IV

Hydroxocobalamin: Initially, 5 g (two 2.5-g vials). A second 5-g dose may be administered, based on the severity of the poisoning and clinical response.

Schilling Test IM or Sub-Q

Cyanocobalamin: Flushing dose is 1000 mcg.

IM

Hydroxocobalamin: Flushing dose is 1000 mcg.

Special Populations

Pregnant Women

RDA for pregnant women is 2.6 mcg daily.

Lactating Women

RDA for lactating women is 2.8 mcg daily.

Requirements increased in lactating women to ensure adequate concentration of the vitamin in milk.

Warnings

Contraindications

  • Known hypersensitivity to vitamin B12, cobalt, or any ingredient in the formulation.
  • No contraindications when used for treatment of cyanide poisoning.

    • Warnings/Precautions

    Warnings

    Hypokalemia

    Fatal hypokalemia reported in intensively treated patients with megaloblastic anemia. Monitor serum potassium concentrations during early vitamin B12 therapy and administer potassium if necessary.

    Polycythemia Vera

    Vitamin B12 deficiency may suppress signs of polycythemia vera; treatment may unmask this condition.

    Ocular Effects

    Avoid use in patients with early Leber’s disease (hereditary optic nerve atrophy); rapid and severe optic nerve atrophy reported.

    Sensitivity Reactions

    Sensitivity Reactions

    Anaphylaxis reported with parenteral preparations.

    Hydroxocobalamin (Cyanokit): Rash, mainly acneiform, reported in 20 or 44% of individuals receiving a 5- or 10-g dose, respectively.

    Skin Test

    Administer an intradermal test dose prior to administration of vitamin B12 for vitamin deficiency in patients who may be sensitive to cobalamins.

    General Precautions

    Laboratory Monitoring

    Obtain hematocrit, reticulocyte count, vitamin B12, folate, and iron levels prior to treatment for vitamin B12 deficiency. Monitor hematologic parameters as necessary during therapy.

    Aluminum

    Some cyanocobalamin injection preparations contain aluminum, which may be toxic. Aluminum may reach toxic levels with prolonged parenteral administration if kidney function is impaired. Premature neonates are particularly at risk because their kidneys are immature, and they require large amounts of calcium and phosphate solutions, which contain aluminum.

    Research indicates that patients with impaired kidney function, including premature neonates, who receive parenteral levels of aluminum >4–5 mcg/kg daily accumulate aluminum at levels associated with CNS and bone toxicity. Tissue loading may occur at even lower rates of administration.

    Benzyl Alcohol in Neonates

    Cyanocobalamin injection may contain benzyl alcohol as a preservative; benzyl alcohol has been associated with toxicity in neonates. (See Pediatric Precautions.)

    Blood Pressure

    Transient elevations in BP reported in individuals receiving IV hydroxocobalamin.

    Undiagnosed Anemia

    Use extreme caution if folic acid is administered to patients with undiagnosed anemia; may obscure the diagnosis of pernicious anemia by alleviating hematologic manifestations of the disease while allowing neurologic complications to progress.

    Renal Effects

    Oxalate crystals observed in the urine of healthy individuals and cyanide poisoning victims following administration of hydroxocobalamin.

    Specific Populations

    Pregnancy

    Category C.

    Lactation

    Distributed into human milk.

    Hydroxocobalamin (Cyanokit): Caution advised; no data available to determine when breast-feeding may be restarted following administration of IV hydroxocobalamin.

    Pediatric Use

    Hydroxocobalamin (Cyanokit): Safety and efficacy not established.

    Cyanocobalamin: Benzyl alcohol has been associated with toxicity (“gasping syndrome”) in neonates; each mL of cyanocobalamin injection (e.g., preparation manufacturered by Abraxis) contains 15 mg of benzyl alcohol.

    Geriatric Use

    Hydroxocobalamin (Cyanokit): No substantial differences in safety and efficacy relative to younger adults. Dosage adjustment not needed.

    Hepatic Impairment

    Hydroxocobalamin (Cyanokit): Safety and efficacy not studied in patients with hepatic impairment.

    Renal Impairment

    Hydroxocobalamin (Cyanokit): Safety and efficacy not studied in patients with renal impairment. Hydroxocobalamin and cyanocobalamin excreted unchanged in urine.

    Common Adverse Effects

    Usually nontoxic even in large doses; mild transient diarrhea, peripheral vascular thrombosis, itching, transitory exanthema, urticaria, body swelling reported in patients receiving parenteral preparations.

    What other drugs will affect Vitamin B12

    Colchicine, aminosalicylic acid and its salts, and excessive alcohol intake lasting >2 weeks may reduce absorption of vitamin B12 from the GI tract.

    Specific Drugs and Laboratory Tests

    Drug

    Interaction

    Comments

    Ascorbic acid

    May destroy substantial amounts of dietary vitamin B12

    Consider this if large doses of ascorbic acid are ingested within 1 hour of administration of oral vitamin B12

    Chloramphenicol

    May antagonize the hematopoietic response to vitamin B12 in vitamin-deficient patients

    Monitor; consider alternate anti-infectives

    Cyanide antidotes

    Safety of concomitant use of hydroxocobalamin with other cyanide antidotes not established

    Caution (See Parenteral under Stability and IV Administration under Dosage and Administration)

    Laboratory parameters determined by colorimetric methods

    Hydroxocobalamin (Cyanokit): Deep red color in blood and/or urine may interfere with certain laboratory tests (e.g., clinical chemistry, hematology, coagulation, urine parameters)

    Consult the product labeling for specific information

    Methotrexate

    Invalidates diagnostic microbiologic blood assays for vitamin B12

    Prednisone

    Increased absorption of vitamin B12 and secretion of IF reported in a few patients with pernicious anemia

    Does not occur in patients with partial or total gastrectomy; clinical importance unknown

    Pyrimethamine

    Invalidates diagnostic microbiologic blood assays for vitamin B12

    Test for intrinsic factor (IF) antibodies

    Prior administration of cyanocobalamin may result in false-positive test results

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