Higher frequency of C.3435 of the ABCB1 gene in patients with tramadol dependence disorder.

Background: Polymorphic variation at the ABCB1 gene has been shown to affect the pharmacodynamics and kinetics of various drugs.

Aim: This study aimed to determine the frequency of occurrence of Single Nucleotide Polymorphism (SNP) in position A118G OPRM1 (rs1799971) gene and C.3435 (rs1045642) gene in tramadol users in comparison with normal controls.

Methods: This was a cross sectional case-control outpatient study. The study sample consisted of 127 subjects (74 tramadol-dependents and 50 healthy controls). All patients fulfilled the Diagnostic and Statistical Manual IV Criteria for substance dependence (on tramadol). Genotyping of the OPRM1 gene 118 SNP and ABCB1 genes C.3435 SNP was performed by PCR, followed by restriction fragment length polymorphism identification.

Results: A significant association was found between the ABCB1 gene T allele at the polymorphic site 3435 and tramadol dependence. No significant association was observed with the A118G OPRM1 gene.

Conclusion: The high frequency of ABCB1 gene T allele present at the polymorphic site 3435 could provide a protective mechanism from tramadol dependence disorder. Further study, using a larger sample, would be useful in further evaluating the possible role of ABCB1 gene polymorphisms.