by a simple effects analysis. An asterisk (*) in the figures indicates a significant simple effect (p < 0.05). Finally, OPRM1 genotype and the interaction between OPRM1 genotype and medication were used as covariates in subsequent models. This added step controlled for the prospective genotyping based on the A118G SNP of the OPRM1 gene and verifies that any novel pharmacogenetic effects persist over and above OPRM1 results.
