其 他 安 全 警 示
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| Singapore: Reminder to verify HLA-B*1502 status in new patients of Asian ancestry before starting carbamazepine treatment (English only) |
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Health Sciences Authority (HSA) reminds healthcare professionals to verify the HLA-B*1502 status before starting carbamazepine (CBZ) treatment in new patients of Asian ancestry. Patients who are HLA-B*1502-positive are at increased risk of developing severe cutaneous adverse reactions (SCARs), particularly Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis (SJS/TEN) during treatment with CBZ.
Genotyping for HLA-B*1502 prior to treatment initiation with CBZ in new patients of Asian ancestry has been the standard of care in Singapore since 2013. This one-time test helps distinguish high-risk patients who should avoid CBZ from low-risk patients who are able to continue to use this low-cost yet effective medicine. The implementation of this recommendation has contributed to a 92% reduction in the number of CBZ-associated SJS/TEN cases in Singapore, from 50 cases in the 5-year pre-implementation period (2008 to 2013) to 4 cases in the post-implementation period (2013 to 2018).
Healthcare professionals are advised to take note of the following:
- HLA-B*1502 genotype testing specifically identifies patients at high risk of developing CBZ-induced SJS/TEN, but not CBZ-induced Drug Rash with Eosinophilia and Systemic Symptoms (DRESS).
- HLA-B*1502 test results should be obtained prior to prescribing CBZ as SJS/TEN can develop and progress in susceptible patients, even after prompt discontinuation of the drug.
- The use of CBZ should be avoided and treatment alternatives are strongly recommended in patients who are found to be positive for HLA-B*1502. As a precaution, these patients should also not be prescribed phenytoin, as there is preliminary data suggesting a suspected association between HLA-B*1502 and phenytoin-induced SJS/TEN.
- Although reported to be rare, patients who test negative for HLA-B*1502 may still be at risk of developing CBZ-induced SJS/TEN. The role of other factors which may contribute to the development of SJS/TEN in these patients, such as drug dose, concomitant medications and co-morbidities, have not been studied.
- Clinical vigilance for CBZ-induced SCARs including DRESS should continue, especially during the first 12 weeks following treatment initiation with CBZ.
Please refer to the following website in HSA for details:
http://www.hsa.gov.sg/announcements/safety-alert/reminder-to-verify-hla-b-1502-status-in-new-patients-of-asian-ancestry-before-starting-carbamazepine-treatment
In Hong Kong, there are 7 registered pharmaceutical products containing carbamazepine. All products are prescription-only medicines. So far, the Department of Health (DH) has received 3 cases of adverse drug reaction related to carbamazepine, of which one case is related to Stevens-Johnson Syndrome. Related news was previously issued by HSA, and was posted on the Drug Office website since 2 May 2013, with the latest update posted on 21 Dec 2016. Letters to inform local healthcare professionals were issued by the DH on 2 May 2013. In Sep 2013, the Registration Committee of the Pharmacy and Poisons Board discussed the matter, and decided that the sales pack label and/or package insert of carbamazepine products should include the relevant safety information. The DH will remain vigilant on safety update of the drug issued by other overseas drug regulatory authorities.
Ends/Thursday, Dec 10, 2020
Issued at HKT 16:00
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