CYANOCOBALAMIN
| CYANOCOBALAMIN (sye-an-oh-koe-bal'a-min) Anacobin  , Bedoz , Nascobal, Rubion Classifications: vitamin b12 ; Therapeutic: vitamin b12 Pregnancy Category: A (PO or nasal spray); C (parenteral) |
Availability
25 mcg, 50 mcg, 100 mcg, 250 mcg tablets; 400 mcg/unit, 500 mcg/0.1 mL nasal gel; 500 mcg/0.1 mL nasal spray
Action
Vitamin B12 is a cobalt-containing b complex vitamin produced by Streptomyces griseus. Essential for normal growth, cell reproduction, maturation of RBCs, nucleoprotein synthesis, maintenance of nervous system (myelin synthesis), and believed to be involved in protein and carbohydrate metabolism. Vitamin B12 deficiency results in megaloblastic anemia, dysfunction of spinal cord with paralysis, GI lesions.
Therapeutic Effect
Therapeutically effective for treatment of vitamin B12 deficiency and pernicious anemia.
Uses
Vitamin B12 deficiency due to malabsorption syndrome as in pernicious (Addison's) anemia, sprue; GI pathology, dysfunction, or surgery; fish tapeworm infestation, and gluten enteropathy. Also used in B12 deficiency caused by increased physiologic requirements or inadequate dietary intake, and in vitamin B12 absorption (Schilling) test.
Unlabeled Uses
To prevent and treat toxicity associated with sodium nitroprusside.
Contraindications
History of sensitivity to vitamin B12, other cobalamins, or cobalt; early Leber's disease (hereditary optic nerve atrophy), indiscriminate use in folic acid deficiency; pregnancy [category A, category C (parenteral)].
Cautious Use
Heart disease, anemia, pulmonary disease.
Route & Dosage
| Vitamin B12 Deficiency Adult: IM/Deep SC 30 mcg/d for 5–10 d, then 100–200 mcg/mo Child: IM/Deep SC 100 mcg doses to a total of 1–5 mg over 2 wk, then 60 mcg/mo Pernicious Anemia Adult: IM/Deep SC 100–1000 mcg/d for 2–3 wk, then 100–1000 mcg q2–4wk Intranasal one pump in one nostril once weekly Child: IM 30–50 mcg/d x 2 wk to total of 1000 mcg, then 100 mcg/mo Infant: IM 1000 mcg/d x at least 2 wk, then 50 mcg/mo Diagnosis of Megaloblastic Anemia Adult: IM/Deep SC 1 mcg/d for 10 d while maintaining a low folate and vitamin B12 diet Schilling Test Adult: IM/Deep SC 1000 mcg times 1 dose Nutritional Supplement Adult: PO 1–25 mcg/d Child: PO <1 y, 0.3 mcg/d; ≥1 y, 1 mcg/d |
Administration
Oral- PO preparations may be mixed with fruit juices. However, administer promptly since ascorbic acid affects the stability of vitamin B12.
- Administration of oral vitamin B12 with meals increases its absorption.
- Give deep SC by slightly tenting the skin at the injection site.
- IM may be given into any normal IM injection site.
- Preserved in light-resistant containers at room temperature preferably at 15°–30° C (59°–86° F) unless otherwise directed by manufacturer.
Adverse Effects (≥1%)
Body as a Whole: Feeling of swelling of body, anaphylactic shock, sudden death. CV: Peripheral vascular thrombosis, pulmonary edema, CHF. GI: Mild transient diarrhea. Hematologic: Unmasking of polycythemia vera (with correction of vitamin B12 deficiency). Metabolic: Hypokalemia. Skin: Itching, rash, flushing. Special Senses: Severe optic nerve atrophy (patients with Leber's disease).Diagnostic Test Interference
Most antibiotics, methotrexate, and pyrimethamine may produce invalid diagnostic blood assays for vitamin B12. Possibility of false-positive test for intrinsic factor antibodies.
Interactions
Drug: Alcohol, aminosalicylic acid, neomycin, colchicine may decrease absorption of oral cyanocobalamin; chloramphenicol may interfere with therapeutic response to cyanocobalamin.Pharmacokinetics
Absorption: Intestinal absorption requires presence of intrinsic factor in terminal ileum. Distribution: Widely distributed; principally stored in liver, kidneys, and adrenals; crosses placenta, excreted in breast milk. Metabolism: Converted in tissues to active co-enzymes; enterohepatically cycled. Elimination: 50–95% of doses ≥100 mcg are excreted in urine in 48 h. Half-Life: 6 d (400 d in liver).Nursing Implications
Assessment & Drug Effects
- Lab tests: Before initiation of therapy, reticulocyte and erythrocyte counts, Hgb, Hct, vitamin B12, and serum folate levels should be determined; then repeated between 5 and 7 d after start of therapy and at regular intervals during therapy. Monitor potassium levels during the first 48 h. Conversion to normal erythropoiesis increases erythrocyte potassium requirement and can result in severe hypokalemia and sudden death.
- Obtain a careful history of sensitivities. Sensitization to cyanocobalamin can take as long as 8 y to develop.
- Monitor vital signs in patients with cardiac disease and in those receiving parenteral cyanocobalamin, and be alert to symptoms of pulmonary edema, which generally occur early in therapy.
- Therapeutic response to drug therapy is usually dramatic, occurring within 48 h. Effectiveness is measured by laboratory values and improvement in manifestations of vitamin B12 deficiency.
- Characteristically, reticulocyte concentration rises in 3–4 d, peaks in 5–8 d, and then gradually declines as erythrocyte count and Hgb rise to normal levels (in 4–6 wk).
- Obtain a complete diet and drug history and inquire into alcohol drinking patterns for all patients receiving cyanocobalamin to identify and correct poor habits.
Patient & Family Education
- Notify physician of any intercurrent disease or infection. Increased dosage may be required.
- To prevent irreversible neurologic damage resulting from pernicious anemia, drug therapy must be continued throughout life.
- Rich food sources of B12 are nutrient-added breakfast cereals, vitamin B12-fortified soy milk, organ meats, clams, oysters, egg yolk, crab, salmon, sardines, muscle meat, milk, and dairy products.
Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; 
Prototype drug