B12 vitamin side effects cyanocobalamin
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Side Effects of Cyanocobalamin (Vitamin B12)
Introduction to Cyanocobalamin
Cyanocobalamin, a synthetic form of Vitamin B12, is essential for maintaining healthy nerves and blood cells and plays a crucial role in DNA synthesis. It is commonly used to prevent and treat Vitamin B12 deficiency, which can lead to conditions such as megaloblastic anemia, characterized by fatigue and weakness 14.
Anaphylactic Reactions to Cyanocobalamin
Rare but Serious Hypersensitivity
Anaphylactic reactions to cyanocobalamin are rare but potentially life-threatening. Several case reports have documented instances where patients experienced severe hypersensitivity reactions following intramuscular injections of cyanocobalamin. These reactions are believed to be either immunoglobulin E (IgE)-mediated or due to sensitization to the Vitamin B12 molecule itself 1458. For instance, a 25-year-old female patient with pulmonary tuberculosis experienced an anaphylactoid reaction after receiving cyanocobalamin injections . Similarly, a 55-year-old woman and a 50-year-old man both had anaphylactic reactions after their second doses of intramuscular cyanocobalamin 45.
Cytotoxicity and Cell Death
Cyanocobalamin [c-lactam] Derivative
The [c-lactam] derivative of cyanocobalamin has been shown to antagonize Vitamin B12 and cause cytotoxicity in HL60 cells, a type of human leukemia cell line. This cytotoxic effect is reversible with additional Vitamin B12 and is linked to the inhibition of methionine synthase and methylmalonyl-CoA mutase, enzymes crucial for cellular metabolism. Methionine supplementation can completely protect cells from this cytotoxicity, highlighting the importance of methionine in mitigating the adverse effects of cyanocobalamin [c-lactam] .
Overdose and Toxicity
Symptoms of Excessive Intake
Excessive intake of cyanocobalamin can lead to toxicity, although such cases are rare. A young woman treated with multiple daily doses of 1 mg of cyanocobalamin for severe pernicious anemia developed symptoms such as acne, palpitations, anxiety, akathisia, facial ruddiness, headache, and insomnia after a total dose of 12 mg. These symptoms resolved two weeks after discontinuing the drug, indicating that while cyanocobalamin toxicity is unusual, it is possible with high doses .
Impact on Renal Function
Risks for Patients with Impaired Renal Function
Cyanocobalamin can accelerate the decline in renal function and increase the risk of cardiovascular events in patients with impaired renal function. Studies have shown that high-dose cyanocobalamin does not benefit patients with impaired renal function for stroke prevention and may even be harmful. However, patients with normal renal function may benefit from B vitamin therapy, suggesting that the form of Vitamin B12 used (e.g., methylcobalamin or hydroxycobalamin) could be crucial in determining its safety and efficacy .
Conclusion
While cyanocobalamin is an effective treatment for Vitamin B12 deficiency, it is not without potential side effects. Rare but serious hypersensitivity reactions, cytotoxicity in specific cell lines, symptoms of overdose, and risks for patients with impaired renal function highlight the need for careful monitoring and consideration of individual patient conditions when administering this form of Vitamin B12. Health care providers should remain vigilant and consider alternative forms of Vitamin B12 where appropriate to mitigate these risks.
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