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Healthcare professionals prescribing vitamin B12 products to patients with known cobalt allergy should advise patients to be vigilant for signs and symptoms of cobalt sensitivity and treat as appropriate.

Review of vitamin B12 and cobalt allergy

Hydroxocobalamin and cyanocobalamin are oral and injectable forms of vitamin B12 that are used to treat vitamin B12 deficiency. Endogenous vitamin B12 and these medicines contain a cobalt component.

The MHRA received a query from a member of the public, as part of a report to the Yellow Card scheme of a suspected reaction associated with vitamin B12 treatment and cobalt allergy. As a result of this, we conducted a review of this topic.

There is evidence within the literature of cobalt sensitivity reactions occurring following administration of vitamin B12. Additionally, the MHRA received three Yellow Card reports including the case described above, which report vitamin B12 as a suspect drug and possible allergic reactions to cobalt. Following the MHRAs review, it was considered appropriate to improve awareness that hydroxocobalamin and cyanocobalamin medicines contain cobalt.

We have subsequently requested relevant Marketing Authorisation Holders (MAHs) to update the?Summary of Product Characteristics?(SmPC) to include that vitamin B12 contains cobalt. We have also requested MAHs to update the?Patient Information Leaflet?(PIL) to advise patients?that cobalt is contained within vitamin B12 and that they should talk to a healthcare professional if they have a known cobalt allergy.

Characteristics of cobalt sensitivity reactions and their management

Patients with a cobalt sensitivity may present with cutaneous symptoms such as chronic or subacute allergic contact dermatitis. Cobalt allergy may also trigger an erythema multiforme-like eruption. ^{[footnote 2]}The hypersensitivity reaction may be immediate or delayed to 12 to 72 hours following exposure. ^{[footnote 3][footnote 4]} Additional vigilance may be required beyond this time period.

There is no alternative treatment for vitamin B12 deficiency, therefore, vitamin B12 use is not contraindicated in patients with cobalt allergy that presents only as cutaneous symptoms. However, where previous serious allergic reaction is established in known cobalt allergy patients, individual assessment of the benefits and risks should be conducted before starting treatment.

Hydroxocobalamin products which are indicated in the treatment of known or suspected cyanide poisoning are excluded from these precautions, considering it is a medical emergency in which the potentially life-saving benefit of treatment would outweigh the risk of allergic reaction.

Patients and carers should be reminded about the symptoms of cobalt sensitivity and to seek medical advice if they experience these symptoms. Symptoms should be monitored and treated as clinically appropriate.

Report suspected reactions on a Yellow Card

Please continue to report suspected adverse drug reactions to nitrofurantoin via the?Yellow Card scheme. Your report will help us safeguard public health. Healthcare professionals, patients, and caregivers are asked to submit reports using the Yellow Card scheme electronically using:

• the?Yellow Card website

• the Yellow Card app; download from the?Apple App Store?or?Google Play Store

• some clinical IT systems for healthcare professionals (EMIS, SystmOne, Vision, MiDatabank, and Ulysses)

When reporting, please provide as much information as possible, including information about batch numbers, medical history, any concomitant medication, onset timing, treatment dates, and product brand name.

Article citation: Drug Safety Update volume 17, issue 5: December 2023: 2.