Anaesthesia => Analgesic
Analgesic, class of drugs that relieve pain without causing loss of consciousness. The drugs include the opium derivatives morphine and codeine, non-opiates (or non-steroidal anti-inflammatory drugs) such as aspirin, acetaminophen, ibuprofen, and paracetamol. Anaesthetics in low doses, or local anaesthetics such as benzocaine, are also analgesic in function. Analgesics are used to relieve a wide range of aches and pains, particularly headaches, toothache, period pain, and rheumatic pain. They may be used in combination-such as aspirin and codeine; ibuprofen and codeine.
Opiate analgesics affect the central nervous system, are addictive, and are used only for severe pain; synthetic opiates such as pentazocine (fortral) are less addictive but may cause hallucinations. The non-opiates act by inhibiting the synthesis of prostaglandins in the body. Aspirin is a good anti-inflammatory agent and is useful for relieving mild and moderate pain and reducing fever, whereas acetaminophen is less effective against inflammation. Ibuprofen is an effective anti-inflammatory drug with a similar effect on prostaglandins as aspirin and has been found to be more effective than aspirin for period pain and toothache. Both ibuprofen and aspirin can irritate the stomach, as well as aggravate high blood pressure and damage the kidneys. Paracetamol is an effective analgesic, but it is still not fully understood how it works. It is thought to inhibit the release of prostaglandins in the central nervous system, rather than at the site of injury or inflammation, as do aspirin and ibuprofen. While paracetamol is safe at normal doses, and is preferred for patients with stomach acidity problems, it is dangerous when taken at doses only minimally higher than the recommended amounts (which may happen when more than one preparation containing the drug is being taken). This is mainly because of its toxic effects on the liver and because symptoms of overdose may be delayed, allowing overdosing to continue. Ibuprofen has been found to be safer than both aspirin and paracetamol in terms of side-effects.
Codeine is often combined with any of the above three. Although the doses available in tablets are known to have minimal analgesic effect, and despite the fact it is sometimes used for types of pain which do not respond to opiate mechanisms but which are prostaglandin-related, codeine combinations are claimed to work by the people who buy them.
Analgesics may also be applied to the skin in the form of gels for muscular aches and pains.
With the discovery of natural opiate receptors in the brain, and of hormones such as endorphins and enkephalins that bind to them, research has been devoted to ways in which these systems could be used to ease pain.