NASCOBAL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for NASCOBAL (NASCOBAL).
Vitamin B12 (cyanocobalamin) is a cofactor for methionine synthase and methylmalonyl-CoA mutase, essential for DNA synthesis, myelin formation, and hematopoiesis.
| Metabolism | Metabolized in the liver via conversion to adenosylcobalamin and methylcobalamin; primarily hepatic metabolism. |
| Excretion | Primarily renal (60-80% as unchanged drug), biliary/fecal (5-10%) |
| Half-life | Approximately 6 days (depot effect due to slow release from injection site); for intramuscular doses, terminal elimination half-life is about 6 days due to gradual absorption |
| Protein binding | High (~90%) bound to transcobalamin II and haptocorrin |
| Volume of Distribution | Vd approximately 0.4-0.6 L/kg; distributes into liver, bone marrow, and other tissues |
| Bioavailability | Intramuscular: 100%; Intranasal: 3-5% relative to intramuscular |
| Onset of Action | Intramuscular: 24-48 hours for improvement in megaloblastic anemia; intranasal: 7-14 days for steady-state levels |
| Duration of Action | Intramuscular: 30-60 days for maintenance of adequate B12 levels; intranasal: requires weekly dosing to maintain levels |
1 spray (500 mcg) intranasally once weekly.
| Dosage form | SPRAY, METERED |
| Renal impairment | No dose adjustment required; not renally eliminated. |
| Liver impairment | No dose adjustment required; not hepatically metabolized. |
| Pediatric use | Not approved for pediatric use; no established dose. |
| Geriatric use | No specific dose adjustment; monitor for adverse effects. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for NASCOBAL (NASCOBAL).
| Breastfeeding | Cyanocobalamin is excreted into breast milk. M/P ratio not established; levels in milk reflect maternal intake. Use is compatible with breastfeeding at recommended doses. |
| Teratogenic Risk | Nascobal (cyanocobalamin) is vitamin B12, an essential nutrient. No teratogenic effects are expected at recommended doses. Adequate maternal B12 levels are critical for fetal neural tube development. Deficiency poses risks; supplementation is safe. |
| Fetal Monitoring |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to cyanocobalamin or any component","Leber's disease (hereditary optic nerve atrophy)"]
| Precautions | ["Hypokalemia and thrombocytosis during initial therapy of pernicious anemia","Anaphylactic shock and urticaria have been reported","Monitor serum potassium and hematologic parameters during treatment"] |
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| Monitor serum B12 levels, homocysteine, methylmalonic acid (MMA) if deficiency suspected. No special fetal monitoring required beyond routine prenatal care. |
| Fertility Effects | No known adverse effects on fertility. Adequate B12 levels are necessary for normal reproductive function. |