## Diagnosis: Vitamin B12 Deficiency Megaloblastic Anemia This patient has classic B12 deficiency with neurological manifestations (paresthesias, glossitis) and megaloblastic morphology. The serum B12 level of 180 pg/mL confirms deficiency. ## First-Line Treatment: Cyanocobalamin **Key Point:** Cyanocobalamin (not hydroxocobalamin) is the standard first-line agent for B12 deficiency in India and most countries. It is the most commonly used form and is cost-effective. **High-Yield:** Standard dosing is 1000 mcg intramuscularly: - Weekly for 6 weeks (loading phase) if neurological symptoms present, OR - Monthly maintenance once B12 stores are replete In this case, given the presence of neurological signs (paresthesias), weekly dosing for 6 weeks followed by monthly maintenance is appropriate. ## Why Cyanocobalamin Over Hydroxocobalamin? | Feature | Cyanocobalamin | Hydroxocobalamin | |---------|---|---| | **First-line in India** | Yes | No | | **Cost** | Lower | Higher | | **Efficacy** | Excellent | Excellent | | **Frequency** | Monthly maintenance standard | Weekly × 6 then monthly (more intensive) | | **Use case** | All B12 deficiency | Preferred in some Western countries for neurological disease | **Clinical Pearl:** Hydroxocobalamin is NOT superior in efficacy and is not routinely used in Indian practice. Cyanocobalamin is the standard of care. **Mnemonic:** **CYANO = Standard** — Cyanocobalamin is the standard first-line B12 replacement globally and in India.
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