Correlation study of genetic variations with the pregabalin as analgesic in patients with chronic low back pain.

Patients meeting the inclusion criteria will be informed of the purpose of the study and included in this after written consent which includes the consent to a blood sample for genomic testing. Patients should make an initial assessment. During the initial assessment will assess pain intensity, functional impairment and sleep disturbance. Thereafter patients should start their treatment, which reads as follows: The first week will take oral tablet Pregabalin dose to 25 mg twice daily followed by oral tablet Paracetamol at a dose of 1 gr twice daily. At the end of the week, patients will be assessed either in person or via telephone questionnaire. The parameters which will be evaluated by the pain intensity sleep quality, the functional impairment and the presence of serious side effects. Regarding side effects, we will first record the incidence of the most common of them, namely peripheral oedema,, dizziness, drowsiness, headache and fatigue, weight gain and dry mouth, horror, blurred vision and diplopias. At the same time these reactions will be evaluated and considered as serious on the basis of either the judgment of the therapist or the patient's discomfort as likely to require treatment discontinuation or dose reduction. If serious adverse reactions occur, patients should discontinue treatment with Pregabalin and will be excluded from the study. Patients that will not appear any serious side effects will pass to the second phase of the study where the dosage of oral tablet pregabalin will be increased to 75 mg twice daily, followed by administering oral tablet paracetamol 1 g twice daily. Similarly those patients will be reassessed one week after starting this regimen for the parameters of the intensity of pain, function, sleep and side effects. If adverse effects occur that were not present in previous regimen, patients should return to this and reassess after 1 week. In patients who will show improvement in the parameters of the intensity of pain, sleep and functionality (>10% reduction in pain and/or sleep and/or functionality scores from previous week), without presenting side effects, the dosage regimen will be increased to oral tablet pregabalin 225 mg daily (75 mg to morning and 150 mg in the evening) followed by oral tablet 1 g paracetamol twice daily, and will be reassessed after one week. If patients experience side effects they will return to the previous regimen and will be reassessed after one week. In patients who show improvement (>10% reduction in pain and/or sleep and/or functionality scores from previous week) without the side effects dosage regimen will be increased to 150 mg twice daily (in combination with 1 g paracetamol twice daily). Similarly if they experience side effects they will return to the previous regimen. In patients who show improvement in the parameters of the intensity of pain, sleep and functionality (>10% reduction in pain and/or sleep and/or functionality scores from previous week), without the side effects, the dosage regimen will be increased to oral tablet 450 mg daily (150 morning 300 evening), together with oral tablet 1 g paracetamol twice daily) and reassessed after one week. If they experience side effects they will return to the previous regimen and they will be reassessed after one week. Finally, in patients who show improvement (10% reduction in pain and/or sleep and/or functionality scores from previous week) without the side effects regimen will increase to oral tablet 300 mg twice daily (in combination with oral tablet 1 g paracetamol twice daily). Similarly if they experience side effects they will return to the previous regimen. Clinically significant result is the improvement of pain intensity, sleep and functionality evaluated with the questionnaire Low Back Pain Disability questionnaire at least 30% percent compared to baseline. Patients' adherence to the treatment with pregabalin will be assessed by checking the empty drug packet return. The total duration of each phase will be 7 days and the total duration of the intervention period will be 6 weekds (6 phases of 7 days each).