Exploratory Study of Cytochrome P450's Pharmacogenomics in Chronic Pain Patients

The use of titrated drugs is at the base of a successful antalgic treatment in order to provide both an adequate relief and a satisfactory tolerability profile. These molecules, though, have a varying degree of efficacy in different subjects due to medical and genetic reasons. The latter are mainly represented by cytochrome (CYP) P450, in particular CYP2D6's polymorphisms are responsible for the diversified metabolism of analgesics used in chronic pain treatments.

Four main types of enzymatic metabolism make up the population, each one defined by a different CYP2D6 allele: extensive metabolizers, ultra-rapid metabolizers, intermediate metabolizers and poor metabolizers.

Moreover, regarding polytherapies, the analgesics' metabolism could be influenced by coadministration of other drugs, thus determining an inhibition or induction of the metabolic enzymes - known as phenocopying - and potentially also a change in the metabolic phenotype itself. The final outcome is the inconstancy of effectiveness and of the risk of developing side effects.

The primary objective of this study is to define a genetic pattern for the gene CYP2D6 by assessing the incidence of poor or ultrarapid metabolizers in a population of chronic pain patients. This will also allow to observe phenocopying in the same population.

Hence 100 patients diagnosed with chronic pain will be enrolled. The genetic pattern of the gene CYP2D6 of such patients will be examined by taking mouth samples. At the same time parametric tests for paired data to survey the correlations between phenotypical patterns and pharmacological therapies will be conducted.