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cyanocobalamin (vitamin B12, Betalin-12, Redisol, Rubramin-PC)

Pharmacology: cyanocobalamin (Betalin-12, Redisol, Rubramin-PC) Indications: 1) vitamin B12 deficiency - pernicious anemia - methylmalonic acidemia 2) increased vitamin B12 requirements due to: a) pregnancy b) thyrotoxicosis c) hemorrhage d) malignancy e) liver disease f) kidney disease Contraindications: Caution: 1) doses exceeding 10 ug/day may produce hematologic response in patients with folate deficiency 2) indiscriminant use may obscure the diagnosis of pernicious anemia 3) isolated vitamin B12 deficiency is rare 4) in the absence of clinical manifestations of deficiency, of no benefit for neurologic or cognitive function in later life [6] 5) vitamin B12 injections of no benefit in improving singing performance [10] Dosage: 1) 2.4 ug QD; 2.6 ug QD if pregnant; 2.8 ug if lactating [11] 1) pernicious anemia: a) start: 1 mg IM QD for 2 weeks b) maintenance: 50 ug IM monthly 2) consider trial of oral* or sublingual vitamin B12 1 mg QD [7] for food-cobalamin malabsorption * oral B12 generally as effective as parenteral B12 [9], but may not be absorbed in patients with: 1) diarrhea 2) gastric or ileal resection Injection: 100 & 1000 ug/mL (10 mL) syringe: 2.5-3 mL/25 g needle 5/8 inch (VA) Tabs: over the counter Adverse effects: 1) not common (1-10%) - diarrhea, itching 2) uncommon (< 1%) - peripheral vascular thrombosis, urticaria, anaphylaxis 3) other a) supplementation of folic acid 0.8 mg, vit B12 0.4 mg & vit B6 40 mg QD - increases risk of cancer - increases risk of dying of cancer - increases all cause mortality - hazzard ratio 1.2-1.4, number needed to harm 40-90 [3] - vit B6 not associated with significant effects [3] - editorialist proposes folic acid as culprit b) use of vitamin B6 (> 20 mg QD) & vitamin B12 (> 55 ug QD) as individual supplements, but not from multivitamins, associated with a 30-40% increase in lung cancer risk among men, but not women [7] Drug interactions: 1) chronic use of nitrous oxide oxidizes cobalamin 2) drugs which interfere with absorption of vit B12 a) neomycin b) colchicine c) ethanol d) metformin (esp without Ca+2 supplementation) 3) chronic proton pump inhibitor use may reduce vitamin B12 levels via inhibition of intrinsic factor secretion 4) high doses of both vit B6 & vit B12 associated with 50% higher risk of high fracture in postmenopausal women [8]

Related

Folgard Rx 2.2 (folate, B12, B6) intrinsic factor; gastric intrinsic factor; IF; INF (GIF, IFMH) Schilling test vitamin B12 deficiency vitamin B12 in serum/plasma

General

vitamin B12; cobalamin

Properties

MISC-INFO: elimination route KIDNEY pregnancy-category C safety in lactation ?

Database Correlations

PUBCHEM correlations

References

  1. Stryer Biochemistry WH Freeman & Co, New York, 1988 pg 508
  2. Prescriber's Letter 12(7): 2005 Oral Vitamin B12 in the Treatment of Vitamin B12 Deficiency Detail-Document#: 210713 (subscription needed) http://www.prescribersletter.com
  3. Ebbing M et al Cancer incidence and mortality after treatment with folic acid and vitamin B12. JAMA 2009 Nov 18; 302:2119. PMID: 19920236 - Drake BF and Colditz GA Assessing cancer prevention studies - A matter of time. JAMA 2009 Nov 18; 302:2152 PMID: 19920243
  4. Deprecated Reference
  5. Department of Veterans Affairs, VA National Formulary
  6. Dangour AD, Allen E, Clarke R et al Effects of vitamin B-12 supplementation on neurologic and cognitive function in older people: a randomized controlled trial. Am J Clin Nutr. 2015 Jul 1. PMID: 26135351
  7. Brasky TM, White E, Chen CL. Long-Term, Supplemental, One-Carbon Metabolism-Related Vitamin B Use in Relation to Lung Cancer Risk in the Vitamins and Lifestyle (VITAL) Cohort. J Clin Oncol. 2017 Aug 22:JCO2017727735. PMID: 28829668
  8. Meyer HE, Willett WC, Fung TT, Holvik K, Feskanich D. Association of high intakes of vitamins B6 and B12 from food and supplements with risk of hip fracture among postmenopausal women in the Nurses' Health Study. JAMA Netw Open 2019 May 3; 2:e193591. PMID: 31074816 https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2733176
  9. Silverstein WK, Lin Y, Dharma C et al. Prevalence of inappropriateness of parenteral vitamin B12 administration in Ontario, Canada. JAMA Intern Med 2019 Jul 15; PMID: 31305876 https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2737914
  10. Shoffel-Havakuk H, Lava CX, Reuven Y et al Effect of Vitamin B12 Injection on the Vocal Performance of Professional Singers. A Randomized, Double-blind, Placebo-Controlled, Crossover Trial. JAMA Otolaryngol Head Neck Surg. 2021;147(1):9-15. PMID: 33180098 PMCID: PMC7662483 Free PMC article https://jamanetwork.com/journals/jamaotolaryngology/fullarticle/2772879
  11. Khardori R Fast Five Quiz: Vitamin B12 Deficiency Medscape. December 22, 2020 https://reference.medscape.com/viewarticle/942750

Component-of

Folgard Rx 2.2 (folate, B12, B6)