Objective: The purpose of this review was to determine how effective different classes of analgesic agents are in the management of chronic pain.
Methodology: The literature search identified five systematic reviews and 18 randomized controlled trials to provide evidence about systemic drug treatment for chronic pain.
Results: Studies in the systematic reviews were mainly of low back pain, and studies in the randomized controlled trials were mainly of fibromyalgia. Other studies investigated of rheumatic pain, musculoskeletal pain, chronic low back pain, and temporomandibular pain. Classes of analgesic agents reviewed were antidepressants, nonsteroidal anti-inflammatory drugs, muscle relaxants, opioid analgesics, and a number of miscellaneous agents.
Conclusions: For chronic pain, opioid analgesics provide benefit for up to 9 weeks (level 2). For chronic low back pain, the evidence shows that various types of nonsteroidal antiinflammatory drugs are equally effective or ineffective, and that antidepressants provide no benefit in the short to intermediate term (level 2). Muscle relaxants showed limited effectiveness (level 3) for chronic neck pain and for chronic low back pain for up to 4 weeks. For fibromyalgia, there is limited evidence (level 3) of the effectiveness of amitryptiline, ondansetron, zoldipem, or growth hormone, and evidence of no effectiveness for nonsteroidal anti-inflammatory drugs, malic acid with magnesium, calcitonin injections, or s-adenyl-L-methionine. For temporomandibular pain, oral sumatriptan is not effective (level 2). The remaining evidence was inadequate (level 4a) or contradictory (level 4b).