HYDROXOCOBALAMIN (VITAMIN B12 ALPHA)

HYDROXOCOBALAMIN (VITAMIN B12 ALPHA)
(hye-drox-oh-koe-bal'a-min)
Hydrobexan, Hydroxo-12, LA-12
Classifications: vitamin b12 antidote;
Therapeutic: vitamin supplement; antidote

Prototype: Cyanocobalamin
Pregnancy Category: A (C if >RDA)

Availability

1000 mcg/mL injection

Action

Cobalamin derivative similar to cyanocobalamin (vitamin B12). More slowly absorbed from injection site than cyanocobalamin and may be taken up by liver in larger quantities. Essential for normal cell growth, cell reproduction maturation of RBCs, myelin synthesis, and believed to be involved in protein synthesis.

Therapeutic Effect

Effective in vitamin B12 deficiency that results in megaloblastic anemia.

Uses

Treatment of vitamin B12 deficiency.

Unlabeled Uses

Cyanide poisoning and tobacco amblyopia.

Contraindications

History of sensitivity to vitamin B12, other cobalamins, or cobalt; indiscriminate use in folic acid deficiency.

Cautious Use

Pregnancy [category A, category C (parenteral)], lactation, children.

Route & Dosage

Vitamin B12 Deficiency
Adult: IM 30 mcg/d for 5–10 d and then 100–200 mcg/mo or 1000 mcg qod until remission and then 1000 mcg/mo
Child: IM 100 mcg doses to a total of 1–5 mg over 2 wk and then 30–50 mcg/mo

Administration

Intramuscular
  • Give deep into a large muscle.

Interactions

Drug: Chloramphenicol may interfere with therapeutic response to hydroxocobalamin.

Pharmacokinetics

Distribution: Widely distributed; principally stored in liver, kidneys, and adrenals; crosses placenta. Metabolism: Converted in tissues to active coenzymes; enterohepatically cycled. Elimination: 50–95% of doses ≥100 mcg are excreted in urine in 48 h; excreted in breast milk.

Nursing Implications

Assessment & Drug Effects

  • Monitor for therapeutic effectiveness: 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 hemoglobin rise to normal levels (in 4–6 wk).
  • Lab tests: Prior to therapy determine reticulocyte and erythrocyte counts, Hgb, Hct, vitamin B12, and serum folate levels; repeated 5–7 d after start of therapy and at regular intervals during therapy.
  • Obtain a careful history of sensitivities. Sensitization can take as long as 8 y to develop.
  • Monitor potassium levels during the first 48 h, particularly in patients with Addisonian pernicious anemia or megaloblastic anemia. Conversion to normal erythropoiesis increases erythrocyte potassium requirement and can result in severe hypokalemia and sudden death.
  • Monitor vital signs in patients with cardiac disease and in those receiving parenteral cyanocobalamin, and be alert to symptoms of pulmonary edema; generally occur early in therapy.
  • Note: Some patients experience mild pain at injection site after administration.
  • Monitor bowel function. Bowel regularity is essential for consistent absorption of oral preparations.
  • Note: Smokers appear to have increased requirements for vitamin B12.

Patient & Family Education

  • Notify physician of any intercurrent disease or infection. Increased dosage may be required.
  • Note: It is imperative to understand that drug therapy must be continued throughout life for pernicious anemia to prevent irreversible neurologic damage.
  • Neurologic damage is considered irreversible if there is no improvement after 1–1? y of adequate therapy.
  • Dietary deficiency of vitamin B12 has been observed in strict vegetarians (vegans) and their breast-fed infants as well as in the elderly.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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