Sunday, May 14, 2017

Cyanocobalamin (Vitamin B12) : Anemia

Availability : Injection 1mg/ml (Pharmaniaga)
Indication & Dosages (FUKKM)
  • Prophylaxis of anaemia associated with Vitamin B12 deficiency
    • 250-1000 mcg IM everymonth
  • Uncomplicated pernicious anaemia or Vitamin B12 malabsorption 
    • Initial 100 mcg daily for 5-10 days followed by 100-200 mcg monthly until complete remission is achieved.
    • Maintenance: up to 1000 mcg monthly. CHILD 30-50 mcg daily for 2 or more
      weeks (to a total dose of 1- 5mg). OR AS PRESCRIBED. 
Alternative dosing (BMJ)
  • Patients with megaloblastic anaemia and pancytopenia require hospital admission
  • An acute regimen of 1000 micrograms cyanocobalamin parenterally is given daily for between 1 and 2 week
  • then 1000 micrograms parenterally once a week for up to 1 month, until significant reticulocytosis is seen in the marrow. 
  • Folic acid supplementation may help reverse the haematological abnormalities 
  • Acute and maintenance treatment of patients with mild to moderate symptoms of vitamin B12 deficiency (haematological: mild anaemia; neurological: dysaesthesia/paraesthesias, polyneuropathy, depression) is with once-daily oral cyanocobalamin or once-monthly parenteral cyanocobalamin
  • In patients treated with oral cyanocobalamin, a response should be seen within 2 months. 
  • If serum vitamin B12 does not rise significantly after 2 months of daily oral cyanocobalamin, clinicians should switch to intramuscular vitamin B12 or consider other causes 
Comparison with Oral route
  • Parenteral therapy using the IM or SC route is by far the most reliable and most familiar treatment for vitamin B12 deficiency
  • oral vitamin B12 in the form of cyanocobalamin in high doses could be absorbed even in patients with pernicious anaemia or significant terminal ileum resection
  • Oral cyanocobalamin has been shown in meta-analysis to be as effective, if not more effective, in patients with vitamin B12 deficiency.
  • Although absorption occurs at dosages <1000 micrograms/day, there appears to be variable absorption and less than maximal clinical and laboratory response.
  • Absorption can be maximised by administering on an empty stomach
References:
  1. MIMS Gateway
  2. http://bestpractice.bmj.com/best-practice/monograph/822/treatment/step-by-step.html

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