Treatment of Vitamin B12 Deficiency Anemia with Co-Prescribed Medications or Nitrous Oxide Use
Several commonly prescribed medicines and recreational nitrous oxide use are established causes of vitamin B12 depletion. When a patient on one of these agents develops B12 deficiency anemia, the treatment approach must account for the ongoing exposure to the causative factor.
Clinical Scenario
This protocol applies to patients with Vitamin B12 deficiency anemia who are currently co-prescribed one or more of the following: colchicine, H2-receptor antagonists, metformin, phenobarbital, pregabalin, primidone, proton pump inhibitors, or topiramate — or who have a history of recreational nitrous oxide use.
Treatment Approach
Management centres on B12 replacement therapy. The route of administration — injectable or oral — is determined by the patient's ability to self-administer. Replacement is continued for as long as the causative medication remains co-prescribed. The complete structured regimen is available via the protocol below.
Clinical Goals
Treatment aims for improvement in symptoms within weeks to months, alongside a prompt rise in haemoglobin level. Response should be monitored; absence of a prompt haematological response warrants further assessment.
References
- CO-PRESCRIBED MEDICATIONS see list on page 4 OR RECREATIONAL USE OF NITROUS OXIDE (NO)
- Co-prescribed medications: colchicine, H2-receptor antagonists, metformin (see the MHRA safety advice), phenobarbital, pregabalin, primidone, proton pump inhibitors, topiramate.
- For patients who can self-administer: IM hydroxocobalamin
- If unable to self-administer: oral cyanocobalamin 50micrograms one tablet daily (taken between meals).
- Advise patients that symptoms may improve within 2 weeks up to 3 months and may initially get worse but should improve with time.
- If there is a failure to respond to therapy i.e. there is not a prompt rise in Hb level.
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