Background and aims: Codeine and tramadol are commonly prescribed weak opioids, which are being metabolised by cytochrome CYP2D6, a polymorphic enzyme associated with differences in metaboiic ability. The aim of this study was to investigate which genetic polymorphisms of CYP2D6 could possibly facilitate prediction of efficacy and safety of these two commonly used opioids in clinical practice. 
Methods: 50 Greek patients were studied, receiving either codeine or tramadol for chronic pain management. The efficacy of treatmet as well as the adverse effects were recorded and correllated to the polymorphisms of CYP2D6. Gonotypes were performed using PCR-RFLP. The effect of polymorphism to the outcome of treatment was correlated to metabolic activity and genotype.
Results: CYP2D6 polymorphisms were significantly correlated with the outcome of opioid treatment (Ρ=0,0003). The carriers of the alleles *4 and *6 characterized as poor metabolizers were significantly associated with the treatment failure. The carriers CYP2D6 genotypes *4/*4, *1/*4, *5/*5, *6/*6 and *10/*10 were associated with the development of adverse  side effects mainly nausea.
Conclusions: Results indicated that reduced activity of CYP2D6 is correlated with low therapeutic efficacy. The pharmacogenomic analysis of CYP2D6 could facilitate personalized pain treatment with opioids such as codeine and tramadol.

CYP2D6 GONOTYPE CAN FACILITATE PREDICTION OF EFFICACY AND SAFETY OF TRAMADOL AND CODEINE TREATMENT. A STUDY ON GREEK POPULATION