8. Treatment with at least two of the following drug classes must have failed to give satisfactory pain relief within the last two years: anticonvulsants e.g., pregabalin, gabapentin); antidepressants (e.g., trazodone, amitriptyline); NSAIDS (e.g., ibuprofen). In addition, at least one of the following must have proved ineffective: exercise-based rehabilitation, massage therapy using a variety of methods, acupuncture using pressure, needles, heat, or electrical stimulation on specific points on the body and psychological interventions such as cognitive therapy.