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Non-opioid analgesics

Created: 1/6/2004
In this category, the non-steroidal anti-inflammatory drugs (NSAIDs) represent a widely used group of drugs. Examples of such drugs are: aspirin, paracetamol, ibuprofen and diclofenac. Paracetamol is included in this group but has very weak anti-inflammatory effects. These drugs are mainly used to treat mild or moderate pain, in general associated with inflammatory processes.  It is also important to note that NSAIDs can be used to treat the severe pain associated with bone metastasis in cancer. It is believed that the analgesic/antipyretic/anti-inflammatory effects of NSAIDs are largely due to inhibition of cyclo-oxygenase (COX), and the resulting inhibition of the synthesis of prostaglandins, which are pro-inflammatory.  COX has two forms: COX-1 and COX-2. COX-1 is a constitutive enzyme, whereas COX-2 is induced at sites of inflammation. The existing NSAIDs are not selective. In particular, it is the inhibition of COX-1 that underlies the majority of unwanted effects of NSAIDs, such as gastrointestinal irritation and bleeding, and nephrotoxicity. In the stomach, the prostaglandins PGE2 and PGI2 inhibit acid secretion and have a gastroprotective action, whereas in the kidney PGE2 and PGI2 act as local vasodilators. Therefore, inhibition of their synthesis reduces renal blood flow and may precipitate acute renal failure. In addition, the prolonged use of NSAIDs is associated with risk of chronic renal failure due to development of interstitial nephritis. For all these reasons, much effort is being devoted at present to the development of better NSAIDs, in particular highly selective COX-2 inhibitors, such as the new drug rofecoxib.

 Aspirin – is analgesic and anti-inflammatory. This is due to the irreversible inhibition of the synthesis of prostaglandins peripherally, at the site of injury. It is unclear whether the effect of aspirin also has a central component.

 Paracetamol – is antipyretic and analgesic, but with negligible anti-inflammatory effects. It is well absorbed after oral administration and does not irritate the gastric mucosa. However, its prolonged use and the ingestion of high doses is associated with significant risk of hepatotoxicity.

 Ibuprofen – has analgesic and anti-inflammatory properties. It may cause less gastric irritation than other NSAIDs.

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