General

Pronunciation:
hye-drox-oh-koe-bal-a-min

Trade Name(s)

• Cyanokit

Ther. Class.

antianemics

vitamins

Pharm. Class.

water soluble vitamins

Indications

• Vitamin B₁₂  deficiency.
• Pernicious anemia.
• Part of the Schilling test (vitamin B₁₂  absorption test) (diagnostic).
• Cyanide poisoning (Cyanokit only).

Action

• Necessary coenzyme for metabolic processes, including fat and carbohydrate metabolism and protein synthesis.
• Required for cell reproduction and hematopoiesis.

Therapeutic Effect(s):

• Corrects manifestations of pernicious anemia (megaloblastic indices, GI lesions, and neurologic damage).
• Corrects vitamin B₁₂  deficiency.
• Reverses symptoms of cyanide toxicity.

Pharmacokinetics

Absorption: Significant protein binding occurs after intravenous administration.

Distribution: Unknown.

Metabolism and Excretion: Primarily excreted unchanged in urine.

Half-life: 26–31 hr.

TIME/ACTION PROFILE (reticulocytosis)

Contraindication/Precautions

Contraindicated in:

• Hypersensitivity;
• Lactation:   Cyanokit: Breastfeeding not recommended.

Use Cautiously in:

•  IM injection: Uremia, folic acid deficiency, concurrent infection, iron deficiency (response to vitamin B₁₂  will be impaired)
• Pedi:  Cyanokit: Safety and effectiveness not established
• OB:  Cyanokit: Use during pregnancy only if potential maternal benefit outweighs potential fetal risk.

Adverse Reactions/Side Effects

IM injection

Derm: itching

F and E: hypokalemia

GI: diarrhea

Local: pain at IM site

Misc: HYPERSENSITIVITY REACTIONS (including anaphylaxis)

Cyanokit

CV: hypertension, chest pain, edema, tachycardia

Derm: erythema, rash, pruritus, urticaria

EENT: dry throat, eye redness, eye swelling

GI: abdominal discomfort, diarrhea, dyspepsia, dysphagia, hematochezia, nausea, vomiting

GU: red urine, acute renal failure

Local: injection site reaction

Neuro: dizziness, headache, memory impairment, restlessness

Resp: dyspnea

* CAPITALS indicate life-threatening.
Underline indicate most frequent.

Interactions

For IM injection only

Drug-Drug

•  Chloramphenicol  and  antineoplastics  may ↓ hematologic response to vitamin B₁₂ .
•  Colchicine,  aminosalicylic acid, or excessive intake of  alcohol, or  vitamin C  may ↓ absorption/effectiveness of vitamin B₁₂ .

Route/Dosage

Vitamin B₁₂  Deficiency (IM only)

IM (Adults): 30 mcg/day for 5–10 days, then 100–200 mcg/mo.

IM (Children): 100 mcg/day for 2 or more wk (to achieve total dose of 1000–5000 mcg), then 30–50 mcg/mo.

Pernicious Anemia (IM only)

IM (Adults): 100 mcg/day for 6–7 days; if improvement, give same dose every other day for 7 doses, then every 3–4 days for 2–3 wk; once hematologic values return to normal (remission), give maintenance dose of 100 mcg/mo.

IM (Children): 30–50 mcg/day for 2 or more wk (to achieve total dose of 1000–5000 mcg), then 100 mcg/mo.

Schilling Test

IM SUBQ (Adults): Flushing dose is 1000 mcg.

Cyanide Poisoning (Cyanokit only)

IV (Adults): 5 g over 15 min; another 5 g dose may be infused over 15–120 min depending upon severity of poisoning (maximum cumulative dose = 10 g).

Availability

Powder for injection (Cyanokit) (requires reconstitution and dilution): 5 g/vial

Solution for injection: 1000 mcg/mL

Assessment

• Assess patient for signs of vitamin B₁₂  deficiency (pallor; neuropathy; psychosis; red, inflamed tongue) before and periodically during therapy.
• Cyanokit: Management of cyanide poisoning should also include establishment of airway, ensuring adequate oxygenation and hydration, cardiovascular support, and seizure management. Monitor BP and HR continuously during and after infusion and immediately report significant changes. The maximal ↑ in BP usually occurs toward the end of the infusion. BP usually returns to baseline within 4 hr of drug administration.

Lab Test Considerations:

• Anemia: Monitor blood smear, red cell indices, plasma folic acid, vitamin B₁₂ , and iron levels, hemoglobin, hematocrit, and reticulocyte count before treatment, after 5–7 days of therapy, 1 mo after the start of therapy, and then every 3–6 mo. Evaluate serum potassium level in patients receiving vitamin B₁₂  for pernicious anemia for hypokalemia during the first 48 hr of treatment. Serum potassium levels and platelet counts should be monitored routinely during the course of therapy.
• Cyanide Poisoning: Monitor CBC, arterial and venous blood gases, serum electrolytes and lactate, renal function, and whole blood cyanide levels.

Implementation

• Usually administered in combination with other vitamins; solitary vitamin B₁₂  deficiencies are rare.

  • Administration of vitamin B₁₂  by the oral route is useful only for nutritional deficiencies. Patients with small-bowel disease, malabsorption syndrome, or gastric or ileal resections require parenteral administration.
• IM 

  Vials should be protected from light.

  • If SUBQ route used, deep SUBQ administration is preferred.
• Intermittent Infusion:  

  Reconstitute each 5 g vial with 200 mL of 0.9% NaCl, D5W, or LR. Gently invert the vial for at least 60 sec prior to infusion. Do not shake. Reconstituted vial can be hung for infusion. Solution is clear dark red; do not administer solutions that are discolored or contain particulate matter.

  • Reconstituted solutions are stable for 6 hr at room temperature. Discard any unused solution after 6 hr.
• Rate: Administer initial 5–g dose over 15 min. Administer additional 5–g dose over 15–120 min.
• Y-Site Incompatibility:
  • ascorbic acid
  • blood products
  • diazepam
  • MORE...
    • dobutamine
    • dopamine
    • fentanyl
    • nitroglycerin
    • pentobarbital
    • propofol
    • sodium nitrite
    • sodium thiosulfate
    • thiopental

Patient/Family Teaching

• Encourage patient to comply with diet recommendations of health care professional. Explain that the best source of vitamins is a well-balanced diet with foods from the four basic food groups.
• Foods high in vitamin B₁₂  include meats, seafood, egg yolk, and fermented cheeses; few vitamins are lost with ordinary cooking.
• Patients self-medicating with vitamin supplements should be cautioned not to exceed RDA. Effectiveness of megadoses for treatment of various medical conditions is unproved and may cause side effects.
• Inform patients with pernicious anemia of the lifelong need for vitamin B₁₂  replacement.
• Emphasize the importance of follow-up exams to evaluate progress.
• Intermittent Infusion:  Advise patient that skin redness may last up to 2 wk and that their urine may remain red for up to 5 wk after drug administration. Instruct patient to avoid sun exposure while their skin is red. Advise patient to contact health care professional if skin or urine redness persist after these time periods. Advise patient that a rash may develop from 7–28 days after drug administration. It will usually resolve without treatment within a few weeks. Advise patient to contact health care professional if rash persists after this time period.

Evaluation/Desired Outcomes

• Resolution of the symptoms of vitamin B₁₂  deficiency.

  • Increase in reticulocyte count.
• Improvement in manifestations of pernicious anemia.
• Resolution of symptoms of cyanide poisoning.