Association of the OPRM1 and COMT genes’ polymorphisms with the efficacy of morphine in Tunisian cancer patients: Impact of the high genetic heterogeneity in Tunisia?

Background Genetic causes for inter-individual variability response to opioids are clinical difficulties for treatment efficiency. The aim of the present study was to investigate the possible association of opioid treatment outcome with single nucleotide polymorphisms (SNPs) in the mμ opioid receptor (OPRM1) and catechol-o-methyltransferase (COMT) genes, in Tunisian cancer pain patients. Methods We genotyped one hundred and twenty-nine cancer patients treated with different doses of morphine for 3 SNPs in OPRM1 gene (rs17174629, rs1799972 and rs1799971) and one in the COMT gene (rs4680). Associations between dose (continuous), dose escalation (yes/no) and SNP or haplotypes were investigated. Results Unlike other studies on Caucasian and Chinese populations, no significant association were found between the 4 polymorphisms screened and the dose of morphine needed for pain relief. Conclusion This result can be explained by the genetic heterogeneity and cosmopolitan areas of our Tunisian patients compared to the others homogenous population.