Chronic Pain Market, By Drug Class (Opioids, Non-steroidal anti-inflammatory drugs (NSAIDS), Anticonvulsants, Antidepressants, and Others), By Indication (Neuropathic pain, Arthritis pain, Chronic back pain, Cancer pain, Migraine, Fibromyalgia, and Others), By Application (Musculoskeletal, Neuropathy, Oncology, and Others), By Distribution Channel (Hospital Pharmacies, Retail Pharmacies, and Online Pharmacies), By Geography (North America, Latin America, Europe, Asia Pacific, Middle East & Africa)