Postoperative painkillers are predominantly non-steroidal anti-inflammatory drugs (NSAIDs) and opioids. NSAIDs may partially relieve moderate to severe pain, but the relief from visceral pain is not ideal and they cannot be used in some patients who are allergic to them. The preferred treatment for moderate to severe postoperative pain is still opioids, which are currently administered according to the WHO’s three-stage pain ladder: step 1 (mild) non-opioid painkillers, step 2 (mild to moderate) weak opioid painkillers (or low-dose strong opioids) plus other adjuvant drugs, step 3 (moderate to severe) strong opioid painkillers plus other adjuvant drugs.
