Influence of genetic polymorphisms on the pharmacokinetics and pharmaco-dynamics of sulfonylurea drugs.

Sulfonylurea drugs including chlorpropamide, gliclazide, tolbutamide, glipizide, glibenclamide (glyburide) and glimepiride are the most widely used oral hypoglycaemic agents in people with type 2 diabetes. This review investigates the impact of genetic polymorphisms on the pharmacokinetics and pharmacodynamics of sulfonylurea drugs. CYP2C9 is the major enzyme involved in sulfonylurea drug metabolism. CYP2C9 variant allele carriers have significant lower apparent clearance of these medicines. CYP2C19 genotype is more influential for gliclazide pharmacokinetics when compared to CYP2C9. Sulfonylurea pharmacodynamics is affected by several genes. Sulfonylurea receptor 1 (SUR1, ABCC8 gene) and K+ inward rectifier Kir6.2 (KCNJ11) have been correlated to significant variation in sulfonylurea response. Diabetics with the SUR1 exon 33 G allele are more sensitive to gliclazide and the rs5210 variant of the KCNJ11 gene was associated with improved clinical efficacy of gliclazide. Carriers of Transcription factor 7-like 2 (TCF7L2) variants are more likely to fail sulfonylurea therapy. On the other hand, patients with HNF-1alpha mutations had a significant greater response to gliclazide when compared to those with type 2 diabetes. The Arg972 polymorphism of insulin receptor substrate 1 (IRS1) may lead to secondary failure of sulfonylurea therapy. Calpain 10 gene (CAPN10) polymorphism has also been linked to sulfonylurea drug response. Despite the available evidence, larger population studies that investigate the pharmacokinetics and pharmacodynamics of sulfonylurea drugs are needed to investigate the influence of key SNPs amidst all potential contributing factors to variability in response to these which inturn will provide information to optimise sulfonylurea use in people with diabetes.