Usage Pattern of Carbamazepine and Associated Severe Cutaneous Adverse Reactions in Singapore Following Implementation of HLA-B*15:02 Genotyping as Standard-of-Care.

In April 2013, the Ministry of Health and Health Sciences Authority of Singapore jointly issued recommendations for HLA-B*15:02 genotyping before starting carbamazepine (CBZ) in new patients of Asian ancestry as standard of care. The Ministry of Health also approved a 75% subsidy for HLA-B*15:02 genotyping to all patients on subsidy at public healthcare institutions. To understand the impact of these regulatory decisions, we researched the usage patterns for CBZ and levetiracetam, the trend of Stevens-Johnson syndrome/toxic epidermal necrolysis [Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN)] reports associated with antiepileptic drugs and the take-up rates of HLA-B*15:02 tests in Singapore. In the 5-year post-policy period, we found that the annual number of reported SJS/TEN cases associated with all antiepileptic drugs was significantly decreased by 57% (p = 0.015); SJS/TEN cases associated with CBZ and phenytoin reduced by 92% and 42% respectively. New CBZ users decreased by 31% while new levetiracetam users approximately doubled. The annual number of HLA-B*15:02 tests conducted increased from 444 to approximately 1,200. Regulatory recommendations for HLA-B*15:02 genotyping as standard of care coupled with government subsidy for the test had contributed to a reduction in CBZ SJS/TEN in Singapore by >90%, in line with that observed in other Asian countries with similar policies. Additionally, the number of phenytoin-SJS/TEN cases also declined. Taken together, this represents a successful example of precision medicine through implementation of a genotyping program to reduce a rare but serious adverse drug reaction among at-risk individuals, while preserving the availability of an effective and low-cost medicine for the broader population.

Adverse Drug Reaction Profile of SGLT2 Inhibitor-Associated Diabetic Ketosis/Ketoacidosis in Singapore and their Precipitating Factors.

BACKGROUND AND OBJECTIVE: As of December 2017, 20 diabetic ketosis (DK)/diabetic ketoacidosis (DKA) cases associated with sodium-glucose co-transporter 2 inhibitors (SGLT2i) had been reported to the Health Sciences Authority (HSA), Singapore. We aimed to provide a detailed analysis of the profile of these cases. METHODS: As part of the emerging safety issue monitoring, the HSA followed up on SGLT2i-associated DK/DKA cases with the reporters to obtain the missing and/or supplementary information. Descriptive statistics were employed to summarise the data collected, while the Mann-Whitney test was employed to evaluate the differences between typical and euglycaemic DKA cases as well as between genders. RESULTS: All cases led to hospitalisation but were non-fatal. Where reported, the majority (71-85%) of DK/DKA cases occurred within 180 days of SGLT2i therapy initiation and involved female patients and/or patients with long-standing type 2 diabetes mellitus (T2DM). Apart from the difference in blood glucose levels, no differences in the profile between the typical and euglycaemic DKA cases were noted. Known precipitating factors were identified in all cases. Acute illnesses, particularly infections and abscesses, were the most commonly reported precipitating factors, followed by insulin dose reduction/cessation. CONCLUSIONS: Based on the profile of the reported cases, it is imperative to maintain clinical vigilance for DK/DKA, especially during the first 6 months of SGLT2i treatment and more so in female patients and/or patients with long-standing T2DM. Prompt evaluation and management of underlying precipitating factors is also important to assess and mitigate the risk of developing DK/DKA during treatment with SGLT2i.

Tailoring of recommendations to reduce serious cutaneous adverse drug reactions: a pharmacogenomics approach.

The Health Sciences Authority launched a pharmacogenetics initiative in 2008 to facilitate evaluation of pharmacogenetics associations pertinent for Chinese, Malays and Indians in Singapore. The aim was to reduce the incidence and unpredictability of serious adverse drug reactions, with a focus on serious skin adverse drug reactions. This paper describes the gathering of evidence and weighing of factors that led to different genotyping recommendations for HLA-B*15:02 with carbamazepine and HLA-B*58:01 with allopurinol, despite both having strong genetic associations. Translation of pharmacogenomics at a national level requires careful deliberation of the prevalence of at-risk allele, strength of genetic associations, positive predictive value, cost-effectiveness and availability of alternative therapies. Our experience provides a perspective on translating genomic discoveries in advancing drug safety.