The gene encoding the mu-opioid receptor (OPRM1) has been reported to associate with a range of substance dependence and HRH2 is the gene coding histamine H2 receptor, the site of action for various compounds, . amitriptiline and mianserin, used in the treatment of psychiatric disorders. Both OPRM1and HRH2 genes contain some single nucleotide polymorphisms (SNPs), including +118A/G in OPRM1 and +398T/C in HRH2, which were reported to change in protein sequences and result in affecting the therapeutic response. .
