cyanocobalamin (Rx, OTC)

>10%

Arthralgia (12%)

Dizziness (12%)

Headache (12%)

Nasopharyngitis (12%)

Frequency Not Defined

Anaphylaxis

Angioedema

Congestive heart failure

Peripheral vascular disease

Pulmonary edema

Diarrhea

Dyspepsia

Polycythemia vera

Sore throat

Nervousness

Rhinitis

Glossitis

Hypoesthesia

Contraindications

Hypersensitivity to product; sensitivity to cobalt

Cautions

Intensive treatment of B12-deficient megaloblastic anemia may cause hypokalemia and sudden death; monitor serum potassium and platelet counts more frequently in these patients

Nasal disease; defer use until symptoms resolve

Injection is incompatible with some common drugs (eg, warfarin and several phenothiazines) but is compatible with vitamins B and C

Vitamin B12 deficiency for >3 months results in irreversible degenerative CNS lesions

Thrombocytosis may occur with treatment of severe vitamin B12 megaloblastic anemia

Oral and intranasal route are not indicated for the treatment of pernicious anemia until symptoms resolve

Vitamin B12 deficiency masks signs of polycythemia vera; vitamin B12 administration may unmask condition; patients exhibiting clinical or hematologic response consistent with polycythemia vera should be referred for further evaluation

IM and SC route used to treat pernicious anemia; oral and intranasal not indicated until hematologic remission and no signs of nervous system involvement

Parenteral product may contain aluminum; toxic aluminum concentrations may occur with renal dysfunction, high doses, or prolonged use

Efficacy of intranasal administration in patients with nasal pathology or concomitant therapy has not been determined; use with caution

Cyanocobalamin products, not recommended for use in patients with Leber’s optic atrophy; for patients with Leber’s disease requiring vitamin B12, consider alternative therapy (eg, hydroxocobalamin) for B12 supplementation; severe and swift optic atrophy reported in patients with early Leber’s disease (hereditary optic nerve atrophy) treated with vitamin B12

Anaphylactic shock and death reported after parenteral vitamin B12 administration; if patients are to start nasal spray before having tolerated cyanocobalamin parenterally, consider administering an intradermal test doseof parenteral vitamin B12 to patients suspected of cyanocobalamin hypersensitivity

Pregnancy

Administration of approved recommended dose is not expected to cause major birth defects, miscarriage or adverse maternal or fetal outcomes

There are risks associated with vitamin B12 deficiency during pregnancy; severe maternal vitamin B12 deficiency during pregnancy may result in adverse pregnancy outcomes such as low birth weight, preterm birth and megaloblastic anemia

Lactation

Vitamin B12 is present in human milk; administration of approved recommended dose is not expected to cause harm to a breastfed child; there is no information on effects the breastfed child or on milk production; developmental and health benefits of breastfeeding should be considered along with mother’s clinical need for drug and any potential adverse effects on breastfed infant from underlying maternal condition

Pregnancy Categories

A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

NA: Information not available.

Mechanism of Action

Coenzyme; metabolic functions include protein synthesis and carbohydrate metabolism

Plays role in cell replication and hematopoiesis

Absorption

Bioavailability: 6.1% (intranasal solution relative to IM)

Distribution

Distributed to liver, bone marrow, and other tissues

Protein bound: Binding to transcobalamins

Elimination

Excretion: Urine (excess amount), bile (mostly reabsorbed)

Prior to treatment, obtain hematocrit, reticulocyte count, vitamin B12, folate, and iron levels; consider potential for concomitant drugs to interfere with vitamin B12 and folate diagnostic blood assays