Fareena Bilwani, Salman N. Adil, Usman Sheikh, Ayesha Humera, Mohammad Khurshid.
Anaphylactic reaction after intramuscular injection of Cyanocobalamin (Vitamin B12): a case report.
J Pak Med Assoc Jan ;55(5):217-9.

We report a case of anaphylactic reaction to intramuscular injection of cyanocobalamin. This 52-yearold lady was diagnosed as a case of megaloblastic anemia secondary to dietary vitamin B 12 deficiency. She had severe anaphylactic reaction after the parenteral administration of cyanocobalamine. Later she received oral vitamin B 12 with no adverse effects. The purpose of this case report is to draw attention to the hypersensitive reaction to injectable vitamin B 12, which is rarely seen. This could be due to sensitization to the vitamin B 12 molecule itself or an IgE mediated reaction. We concluded that anaphylactic reaction to vitamin B 12 is a rare but serious side effect and it should be kept in mind while the drug is being administered to the patient, especially via the parenteral route.

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