Influence of KCNH2 Polymorphisms on the QTc Interval in Kelantanese Malays Patients Receiving Methadone Maintenance Therapy (MMT) in Malaysia

Methadone maintenance therapy (MMT) is one of the modalities to prevent HIV transmission among injected drug users, particularly in opioid-dependent users. However, methadone-associated cardiotoxicity is one of the fatal adverse events that limit the widespread usage in certain groups of opioid-dependent patients. This is a cross-sectional study aimed to investigate the association between 4 KCNH2 SNPs (1539C>T, in exon 6 of KCNH2 gene; 1956T>C, in exon 8 of KCNH2 gene), 2350C>T (in exon 9 of KCNH2 gene), 2690A>C (Exon 11 of KCNH2 gene)) and prolongation of QTc interval in opioid-dependent Kelantanese Malays who are the recipients of Methadone Maintenance Therapy. The investigators hypothesized that subjects with minor alleles of those 4 SNPs will have longer QTc intervals than those with major alleles, adjusting for the effects of other confounding factors such as age and gender of the subjects, plasma methadone trough levels, hypokalemia, hypocalcemia and hypomagnesemia. The investigators also aimed to provide a model that will reliably predict the magnitude QTc based on the SNPs data and other covariates mentioned above. This will greatly assist in identifying methadone recipients who are at risk of developing prolonged QTc or the more fatal torsade de pointes.