ABSTRACT
Some pain is good—it helps protect against further damage. Nociceptive and inflammatory pains are adaptive and protective. When problems develop in parts of these complex pathways, chronic pathological pain occurs. Opioids are often used for chronic pain, but they can show tolerance and have potential for addiction. They also cause respiratory depression, constipation, drowsiness, and the inability to focus. For mild to moderate pain and fever, acetaminophen is effective and is widely used for children. Its mechanism of action is still unclear and may have many different targets. The many potential mechanisms for acetaminophen may be related to a complex series of metabolites formed from the parent compound. One metabolite in particular is of interest, as it mimics actions of endogenous cannabinoids. Another metabolite, however, can cause hepatotoxicity.
Aspirin and the other NSAIDs are also commonly used for fever and mild to moderate pain. These drugs differ from acetaminophen in that they block prostaglandin synthesis and suppress portions of the inflammatory response. The traditional NSAIDs block the activity of the constitutive COX-1 and the inducible activity of COX-2. To minimize the side effects associated with blocking COX-1, COX-2 inhibitors were developed. However, safety concerns with the COX-2 inhibitors have led to their removal from the market. Although some COX-2 inhibitors have once again become available, their manufacturers give warnings about their safety. NSAIDs should probably only be taken for brief intervals. They may help decrease the severity of an injury in the first 24 to 48 hours by suppressing part of the inflammatory response; however, the inflammatory response is a normal process that works to heal and repair the damage, and extended NSAID use could be counterproductive. Prophylactic use of NSAIDs is also being questioned, as the moderate reduction in pain they provide is countered with increased markers of muscle damage. In addition, undesirable effects on the kidneys cause fluid and salt balance problems. Ice and rest sometimes are the best methods of helping the body heal.
