1. Pain Clinic, Department of Anesthesia and Reanimation Hospital Universitari de Bellvitge L'Hospital et de Llobregat Spain
2. Pain Clinic Hospital Universitario Virgen de las Nieves Granada Spain
3. Pain Clinic, Department of Anesthesia and Reanimation Hospital Povisa Vigo Spain
4. Centro de Salud Puerta del Ángel Madrid Spain
5. Clinical Pharmacology Hospital de la Princesa Madrid Spain
6. Pain Clinic Hospital de la Princesa Madrid Spain