TJU/Education/Anesthesiology/Digital Library/Acute Postoperative Pain Management

Digital Library - Acute Postoperative Pain Management

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Nonopioid Analgesics

Aspirin, acetaminophen, and NSAIDS are the principal non-opioid analgesics used to treat minor to moderate acute postoperative pain. The majority of non-opioid analgesics inhibit the enzyme cyclooxygenase which is one of the first steps in creating prostaglandins. As we discussed earlier, prostaglandins lower the threshold for activation of peripheral nocioceptors, therefore by inhibiting cyclooxygenase we can effectively modulate nocioception in the periphery.

Common side effects include nausea, vomiting, and dyspepsia. Prolonged bleeding secondary to platelet inhibition may be undesirable in post op surgical patients. More severe, but far more rare, side effects include bronchospasm, gastrointestinal bleeding, and acute renal insufficiency. In addition, acetaminophen is hepatotoxic in large doses. Patients must be cautioned to limit the dose of acetaminophen in the postoperative period.

Unlike the opiod analgesics, the mechanism of action does not involve interrupting the transmission of the nocioceptive stimulus, but only in decreasing the sensitivity to the inflammatory response to tissue injury. This property can serve to enhance analgesia when the nonopioids are combined with opioids. This is seen with the combination of acetaminophen with various forms of codeine. The analgesic effects of the nonopioids characteristically exert a ceiling effect which is a result of their narrow therapeutic range. After a certain dose there is little increase in analgesia but a considerable increase in toxicity.