Subjects and methods of our retrospective study from which unpublished data were obtained for inclusion in analysis are as follows. Fifty six methadone maintenance opioid-dependent and 83 healthy control subjects were included. These subjects participated in a number of clinical studies (including a pregnancy study) conducted within the discipline of pharmacology at the University of Adelaide from January 2001–2007, during which written informed consent and whole blood or tissue samples for the genotyping analysis were obtained. Approval for all studies was obtained from the Royal Adelaide Hospital Research Ethics Committee. Original study case notes were used to obtain subject demographic data. Genomic DNA was isolated from samples using a QIAamp® DNA mini kit according to the manufacturer’s instructions (QIAGEN Pty Ltd, Doncaster, VIC, Australia). Genotyping of the A118G SNP was performed using allele-specific polymerase chain reaction (PCR) as previously described.15
