Adverse effects associated with non-opioid and opioid treatment in patients with chronic pain

Chronic pain is a debilitating condition that is associated with many common diseases; this places a major burden on the healthcare system. There are currently numerous analgesic agents available for the treatment of chronic pain. In general, the oral non-opioid analgesic, paracetamol, is recommended for the initial treatment of mild to moderate pain. Therapeutic doses of paracetamol do not appear to result in hepatotoxicity, although overdose may lead to acute liver failure. Current data suggest that paracetamol has acceptable gastrointestinal tolerability. Another class of non-opioid analgesic with confirmed efficacy for the treatment of chronic mild to moderate pain are non-steroidal anti-inflammatory drugs (NSAIDs), although this efficacy is offset by the potential of adverse gastrointestinal events. In particular, non-selective NSAIDs, also known as cyclooxygenase (COX) inhibitors, carry an increased risk of serious upper gastrointestinal complications, including ulcers, perforation and bleeding. The introduction of COX-2 inhibitors provided a NSAID-based option with improved gastrointestinal safety, but increased risk of cardiovascular effects. Opioids are powerful analgesic agents used to treat moderate to severe chronic pain. However, treatment with opioids is associated with a number of common adverse effects, including constipation, nausea or vomiting, pruritus, somnolence or cognitive impairment, dry mouth, tolerance or dependence and urinary retention. Although there are multiple strategies in place to manage adverse events that arise from both non-opioid and opioid analgesic therapy, a better understanding of the mechanisms involved in the development of specific drug-related adverse effects is required along with proper prescribing practices and adequate physician/patient education. Balanced against the adverse effects of pain management medications, there is a need to be mindful of the widespread, often serious, adverse consequences of poorly managed pain itself.