Other safety alerts
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| Singapore: HLA-B*1502 genotype testing: Towards safer use of carbamazepine |
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The Health Sciences Authority (HSA) reviewed that on 30 April 2013, a Dear Healthcare Professional Letter (DHCPL) was jointly issued by the Ministry of Health (MOH) and HSA to highly recommend genotyping for HLA-B*1502 allele prior to initiation of carbamazepine (CBZ) therapy in new patients of Asian ancestry, as genotyping for this group of patients is now considered the standard of care. This recommendation was based on both local and international data supporting a strong association between HLA-B*1502 and CBZ-induced Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN).
Healthcare professionals are reminded to take note of the following:
• CBZ is indicated for the treatment of epilepsy and other conditions such as bipolar disorders, alcohol-withdrawal syndrome, trigeminal neuralgia, diabetic neuropathy and diabetes insipidus centralis. Testing for the presence of HLA-B*1502 allele is highly recommended in new patients of Asian ancestry, regardless of the indication for which the drug is used.
• CBZ should not be prescribed prior to the return of HLA-B*1502 test results. This is because of the possibility of development and progression of SJS/TEN in susceptible patients even after prompt discontinuation of the drug.
• The use of CBZ should be avoided and treatment alternatives are recommended in patients who are found to be positive for HLA-B*1502. Preliminary data have shown a suspected association between this allele and phenytoin-induced SJS/TEN, although the effect size is not as large. As a precaution, patients who are identified to be positive for the HLA-B*1502 allele should also not be prescribed phenytoin.
• Genetic testing should not substitute for appropriate clinical vigilance and patient management. Although rare, patients negative for HLA-B*1502 could still develop SJS/TEN as the role of other factors such as drug dose, concomitant medications and co-morbidities have not been studied.
Please refer to the following website in HSA for details:
http://www.hsa.gov.sg/publish/hsaportal/../hla-b_1502_genotype.html
In Hong Kong, there are 10 registered pharmaceutical products containing carbamazepine and are prescription-only medicines. Related news has been released by the HSA and was posted on the website of Drug Office on 2 May and 30 August 2013. A letter to inform healthcare professionals to draw their attention on the issue and urge them to report any adverse drug reaction related to the drug was issued on 2 May 2013. The matter was discussed by the Registration Committee of the Pharmacy and Poisons Board and concluded in the meeting held in September 2013 that the package insert of product containing carbamazepine should include the new safety information in-line with Singapore.
Ends/ Saturday, January 4, 2014
Issued at HKT 14:30
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