1. Pain Treatment Unit Doña Mercedes Primary Health Care Center Dos Hermanas Spain
2. Hospital Valle Del Guadalhorce Pizarra, Málaga Spain
3. Departamento de Farmacología Facultad de Medicina Universidad de Málaga Málaga Spain
4. Alcudia Primary Health Care Center Alcudia, Mallorca Spain
5. Support Research Unit Costa del Sol Hospital Marbella Spain
6. Research Network for Health Services in Chronic Diseases (REDISSEC) Madrid Spain