Genome-wide association studies (GWASs) survey the entire catalog of common genetic variants in a hypothesis-free manner. OPRM1 is an obvious gene of interest, but prior studies of complex traits have repeatedly demonstrated that unbiased approaches are important for discovering phenotypically relevant SNPs.24–26 We performed a GWAS to search for pharmacogenetic determinants of daily methadone dose in a sample of methadone-treated OD subjects, and followed-up our findings using morphine dose data from an independent clinical sample being treated for acute pain. In this way, we sought to identify and characterize SNPs that associate with therapeutic opioid dose, which could enable personalized treatment of individuals based on their genotype.
