Cyanocobalamin
vit B12
Pronunciation: sye-an-oe-koe-BAL-a-min
“Cyan & cobalt B12-pack”
What it isVitamin B12 for one-carbon metabolism and myelin maintenance; deficiency and pernicious anemia.
Why this oneHigh-dose oral therapy works even in pernicious anemia through passive absorption, so injections are rarely necessary now.
What limits itThe hematological response comes quickly but neurological recovery may be incomplete if treatment was delayed — the reason to check B12 before giving folate.
FDA-approved for
- vitamin B12 deficiency
Principal riskNeurological recovery may be incomplete if delayed
Classes and tags
Clinical profile
Legacy pregnancy categoryA
Defining liabilityUsually well tolerated at replacement doses; excessive dosing can cause agent-specific metabolic or organ toxicity.
FDA label
Read the full label on DailyMed ↗
NO BOXED WARNINGS
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Pernicious (Addisonian) anemia / B12 malabsorption | Adults | 100 mcg IM/deep SC QD × 6–7 days | If response: 100 mcg every other day × 7 doses, then q3–4 days × 2–3 wk; then 100 mcg monthly for life | Undefined |
| B12 deficiency, normal intestinal absorption (oral route not adequate) | Adults | Initial treatment similar to pernicious anemia, per severity | Chronic: switch to oral B12 | Undefined |
| Schilling test (B12 absorption test) | Adults | 1000 mcg once (flushing dose) | 1000 mcg once | 1000 mcg once |
Renal Undefined (aluminum may accumulate with impaired kidney function)
Hepatic Undefined
Instructions
- IM or deep SC only; avoid IV (vitamin lost in urine)
- Intradermal test dose if sensitivity suspected
- Give folic acid concomitantly if needed
- Inspect for particulate matter/discoloration
Available strengths
- inj 1000 mcg/mL
Contraindications
- Sensitivity to cobalt and/or vitamin B12
Cautions
- Early Leber's disease: severe, swift optic atrophy
- Hypokalemia/sudden death with intense treatment of severe megaloblastic anemia
- Anaphylactic shock and death (test dose if suspected sensitivity)
- Benzyl alcohol: gasping syndrome in premature infants
- Aluminum toxicity with impaired kidney function
- Folic acid may mask B12 deficiency; monitor K+ first 48 h
Adverse reactions
- Pulmonary edema / CHF early in treatment
- Peripheral vascular thrombosis
- Polycythemia vera
- Mild transient diarrhea
- Itching
- Transitory exanthema
- Feeling of swelling of entire body
- Anaphylactic shock
Pregnancy Category C; no adequate studies; B12 requirements increase in pregnancy (4 mcg daily recommended)
Lactation Excreted in human milk; 4 mcg daily recommended during lactation
Cost
| Strength | #/mo | generic $/unit | CostPlus | |
|---|---|---|---|---|
| 1000 mcg/mL | inj | per unit | $1.47/mL | not offered |
Generic entry1983
Active metabolites
Open Cyanocobalamin in the interactive console ↗
Self-check
- How can high-dose oral B12 work in pernicious anemia?
Passive absorption. - What recovery may remain incomplete after delayed B12 treatment?
Neurological recovery.