Codeine and its alternates for pain and cough relief. I. Codeine, exclusive of its antitussive action.

This report-the first of a series on codeine and its alternates for pain and cough relief-presents a detailed evaluation of experimental and clinical data concerning the analgesic action of codeine (the antitussive action will be assessed separately). The authors discuss the pharmacology of the drug, including side-effects and toxicity; effects on the respiratory, circulatory, digestive and urinary systems; tolerance, dependence and liability to abuse; metabolic effects; and mechanism of action.Though codeine is generally more toxic than morphine to animals on account of its convulsant action, it is less toxic to man, possibly because it produces less respiratory depression. Again, tolerance to its analgesic effects has been demonstrated in several animal species, but dependence in man is observed far less frequently than it is with morphine, and the abstinence syndrome is less intense. From their extensive review of the evidence available, the authors conclude that codeine is a good analgesic and that little risk to public health is likely to arise from its clinical use to relieve pain.