其 他 安 全 警 示
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| The United Kingdom: Vitamin B12 (hydroxocobalamin, cyanocobalamin): advise patients with known cobalt allergy to be vigilant for sensitivity reactions (English only) |
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Medicines and Healthcare products Regulatory Agency (MHRA) announces that there are case reports in the literature describing cobalt sensitivity-type reactions in patients being treated for vitamin B12 deficiency.
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, the MHRA 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 MHRA’s review, it was considered appropriate to improve awareness that hydroxocobalamin and cyanocobalamin medicines contain cobalt.
The MHRA has subsequently requested relevant Marketing Authorisation Holders (MAHs) to update the Summary of Product Characteristics (SmPC) to include that vitamin B12 contains cobalt. The MHRA has 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.
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. The hypersensitivity reaction may be immediate or delayed to 12 to 72 hours following exposure. 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.
Advice for healthcare professionals:
- Cobalt sensitivity reactions typically present with cutaneous symptoms of chronic or subacute allergic contact dermatitis. Infrequently, cobalt allergy may trigger an erythema multiforme-like reaction. Symptom onset may be immediate or delayed up to 72 hours post-administration.
- Cobalt allergy is estimated to affect 1 to 3% of the general population.
- If cobalt sensitivity-type reactions occur, assess the individual benefits and risks of continuing treatment and, if necessary to continue, advise patients on appropriate management of symptoms.
Please refer to the following website in MHRA for details:
http://www.gov.uk/drug-safety-update/vitamin-b12-hydroxocobalamin-cyanocobalamin-advise-patients-with-known-cobalt-allergy-to-be-vigilant-for-sensitivity-reactions
In Hong Kong, there are registered pharmaceutical products for human use which contain vitamin B12 substances in oral and injectable forms, including hydroxocobalamin (4 products), cyanocobalamin (73 products) and mecobalamin (5 products). Two of these products contain both hydroxocobalamin and cyanocobalamin. So far, the Department of Health (DH) has received one case of adverse drug reaction related to cyanocobalamin, but this case was not related to cobalt sensitivity. The DH has not received any case of adverse drug reaction related to hydroxocobalamin or mecobalamin. In light of the above MHRA’s announcement, letters to inform local healthcare professionals will be issued, and the matter will be discussed by the Registration Committee of the Pharmacy and Poisons Board.
Ends/Tuesday, Dec 19, 2023
Issued at HKT 15:30
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