This meta-analysis evaluates the effectiveness and side effects of opioids for chronic noncancer pain (CNCP). The study included 41 randomized controlled trials involving 609 patients with CNCP, primarily characterized by nociceptive or neuropathic pain. The analysis found that opioids were more effective than placebo in reducing pain and improving function in patients with nociceptive or neuropathic pain or fibromyalgia. Strong opioids (morphine, oxycodone) were significantly more effective than weak opioids (tramadol, propoxyphene, codeine) and other drugs like naproxen and nortriptyline for pain relief. Common side effects included constipation, nausea, dizziness, somnolence, vomiting, and dry skin. The study highlights the need for well-designed equivalence trials to compare opioids with other nonopioid drugs and emphasizes the importance of long-term follow-up to assess potential adverse effects such as addiction and sexual dysfunction.This meta-analysis evaluates the effectiveness and side effects of opioids for chronic noncancer pain (CNCP). The study included 41 randomized controlled trials involving 609 patients with CNCP, primarily characterized by nociceptive or neuropathic pain. The analysis found that opioids were more effective than placebo in reducing pain and improving function in patients with nociceptive or neuropathic pain or fibromyalgia. Strong opioids (morphine, oxycodone) were significantly more effective than weak opioids (tramadol, propoxyphene, codeine) and other drugs like naproxen and nortriptyline for pain relief. Common side effects included constipation, nausea, dizziness, somnolence, vomiting, and dry skin. The study highlights the need for well-designed equivalence trials to compare opioids with other nonopioid drugs and emphasizes the importance of long-term follow-up to assess potential adverse effects such as addiction and sexual dysfunction.