DNA preparation and genotyping
HT
Genomic DNA was isolated from blood using the QIAamp DNA micro kit (Qiagen, Germany) according to the manufacturer’s protocol. The OPRM1 A118G SNP (rs1799971) was detected by a TaqMan SNP Genotyping Assay (C_8950074_1; Applied Biosystems, Carlsbad, California) on an ABI 7900 HT RT‐PCR system with SDS 2.2.2 software (10 μl reaction volume containing 10 ng genomic DNA, 40 cycles of 95 °C for 15 s, and 60 °C for 1 min).Naltrexone and 6ß-Naltrexol blood levels were quantified by chromatography and mass spectrometry. Methodological details are provided in the supplement.