Vitamin B12 desensitization and provocation: Ten-year clinical experience

Vitamin B12 is an essential micronutrient and hypersensitivity reactions (HSR) are considered rare.

To present the characteristics of HSRs to vitamin B12 preparations and to report the outcomes of desensitization and drug provocation tests (DPT) for vitamin B12.

The retrospective descriptive study included patients who required treatment for vitamin B12 deficiency and were hypersensitive to vitamin B12 or hesitant to use it due to other drug allergies. Low-risk patients based on their index reaction and patients hesitant to use vitamin B12 underwent DPT, while desensitization protocols were performed for patients classified as high-risk. Successful completion defined as the execution of all steps in the desensitization and DPT protocols without any subsequent immediate or delayed reactions.

Among the 44 patients, 28 patients (63.6%) had a history of HSRs following the use of cyanocobalamin. The remaining 16 patients (36.4%) had no prior history of HSR to vitamin B12-containing drugs but were hesitant to use vitamin B12 due to other drug allergies. DPT was performed in 38 patients (86.4%), while desensitization was performed in 6 patients (13.6%). The mean age was 46.34 ± 14.50 years and 32 (72.7%) of them were female. Skin prick tests (SPT) and immediate reading intradermal tests (IDTs) were administered in 20 patients (45.5%). Patch tests were conducted in 8 patients (18.1%) and delayed reading IDTs were performed in 3 (6.8%). All skin test results were negative. A total of 40 challenges were conducted and an immediate-type HSR was observed in 1 challenge (2.5%). Desensitization was performed in 8 cycle and HSR occurred in 1 (12.5%) cycle.

DPT is a reliable procedure that provides the assessment of low-risk patients with vitamin B12 hypersensitivity and prevents unnecessary drug restrictions. Additionally, desensitization protocols enable the continuation of vitamin B12 treatment in high-risk patients.