Eleven SNPs were chosen from the dbSNP and Celera genomics database with the following criteria: (1) SNPs located in coding or regulatory regions of the gene or reported associated with drug dependence in literature; (2) haplotype-tagged SNPs suggested by HapMap database [25] or SNPbrowser™ Software 3.0 [26] using the default parameters; and (3) SNPs with minor-allele frequency ≥ 0.10 in the dbSNP database. SNP rs1799971 is a non-synonymous variant (Asn40Asp) located in exon 1. Other SNPs are located in intronic regions of OPRM1. Table 1 listed the characteristics of the selected SNPs.
