Showing papers on "Antitussive Agent published in 1984"

Dextromethorphan and codeine: comparison of plasma kinetics and antitussive effects.

Abstract: Plasma kinetics of dextromethorphan (as dextrorphan ) and codeine were investigated after acute oral doses in 8 patients with pathological cough; after which the patients participated in an acute dose-response study of the antitussive effects of each drug administered as syrups. Maximum plasma codeine concentrations averaged 384 ng.ml-1 (s.d. +/- 78.3) occurring between 0.75 and 2h after ingestion of 60 mg codeine phosphate; in comparison mean peak plasma dextrorphan levels were 386 ng.ml-1 (s.d. +/- 107.2) and 388 ng.ml-1 (s.d. +/- 101.3) respectively, after administration of 60 mg dextromethorphan syrup and tablet formulations. Bioavailability of dextromethorphan tablets was comparable to syrup. No correlation emerged between instantaneous plasma concentrations of either dextrorphan or codeine and antitussive responses; however, peak antitussive effect was significantly related to log dose with both drugs. Antitussive effects of 30 mg codeine phosphate and 60 mg dextromethorphan hydrobromide did not differ significantly; both were superior to 30 mg dextromethorphan hydrobromide and placebo.

ABC of poisoning. Respiratory drugs.

Abstract: [lheophlIine clearance Of the drugs prescribed for respiratory disorders theophylline stands out as the one that most often causes severe toxicity, whether due to iatrogenic accidental, or deliberate poisoning. Theophylline (the active constituent of aminophylline) is a smooth muscle relaxant and inhibits inflammatory mediator release from mast cells. In addition to its use as a bronchodilator it is less commonly used in the treatment of primary apnoea of the newborn and in heart failure. Adverse effects occur relatively often because it has a narrow therapeutic index and there is also a wide interindividual variability in theophylline clearance. Knowledge of the factors affecting clearance and use of the now widely available assays for measuring plasma theophylline concentrations should enable theophylline doses to be more precisely tailored to the individual patient. In the premature neonate relatively more theophylline is metabolised to caffeine, which has a similar effect to theophylline. If caffeine measurements are not available 10-15 mg theophylline per litre should be regarded as the top of the therapeutic range for neonates. Iatrogenic poisoning has occurred because of miscalculation of dosage and occasionally because of the simultaneous prescription of two or more proprietary preparations containing theophylline. Most iatrogenic theophylline toxicity can be managed conservatively but some severe overdoses in neonates and children have, rarely, required active elimination procedures such as haemodialysis.