Simple analgesics.

A number of drugs are available that act fairly specifically as "mild" analgesics, although this description by no means implies that their clinical effectiveness is limited to the relief of slight pain and trivial disability. They are effective by mouth and their action is mediated peripherally. Among the possible mechanisms of action, the inhibition of prostaglandin synthesis is currently regarded as most likely to be relevant. Some centrally acting drugs of the narcotic analgesic type, such as codeine and dextropropoxyphene are effective orally; they are usable in the same way as other mild analgesics and may be preferable for some types of pain. Many problems arise in the assessment and comparison of mild analgesics, both experimentally and clinically. Subjective assessments may be made on a pain scale by the patient himself, or by a trained observer. Individual variations are all-important, and the limitations of controlled trials need to be remembered. Alternative drugs and mixtures have little advantage over aspirin, but specific drug tolerance, in the long term, varies from patient to patient. Gastric irritation is most likely to occur with aspirin in the presence of chronic dyspepsia or acute precipitating causes such as alchoholic gastritis. Allergy also occurs in some susceptible individuals. The risk of renal damage with phenacetin is increasingly appreciated, and the possibility of hepatic damage from paracetamol is now recognised. Other side-effects and interactions are summarized in the review, and some notes are given on therapeutic and non-therapeutic use.