Mostafa N, et al. - In view of the observation that the most important site is human mu-opioid receptor (OPRM1) for the analgesic effect of opioids, researchers here examined both patients and healthy controls for polymorphism in Mu opioid receptor gene (OPRM1') by a genetic study. Further, substance use was assessed in patients using the Addiction Severity Index while urine screen was asked for controls. The single nucleotide polymorphisms (SNP) database of the National Centre for Biotechnology Information, and the life technologies SNP database were reviewed for the SNP. The analysis revealed no correlation of the use of opiates with OPRM1 and the presence of the polymorphic gene with the different clinical characteristics of the opiate use.