title: A modified ultraviolet spectrophotometric method for the determination of theophylline in serum in the presence of barbiturates.
abstract: Ultraviolet spectrophotometry is the most commonly used technique for the determination of theophylline levels for therapeutic monitoring. Common interferences in most methods are barbiturates and xanthines. A modified method which eliminates interferences from barbiturates and most xanthines is presented. Theophylline is extracted from serum with chloroform/isopropanol at pH 7.4 back extracted into dilute hydrochloric acid and then the solution is made alkaline with sodium hydroxide. Barbiturate interferences are eliminated. Interference from caffeine, uric acid, 7-(2,3-dihydroxypropyl)theophylline, xanthine, and hypoxanthine are not observed. Theobromine, and the metabolite 3-methylxanthine interfere. Interference is not observed from quinidine, diazepam, salicylate, glutethimide, methylprylon, propranolol, methaqualone, dilatin and ethchlorvynol. Sulfanilamide, procainamide and chlordiazepoxide interfere.
mesh_terms: D001463:Barbiturates / Q000097:blood*; D002110:Caffeine / Q000097:blood; D006801:Humans; D007042:Hypoxanthines / Q000097:blood; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013806:Theophylline / Q000097:blood*; D014527:Uric Acid / Q000097:blood; D014970:Xanthines / Q000097:blood
chemical_list: D001463:Barbiturates; D007042:Hypoxanthines; D014970:Xanthines; D014527:Uric Acid; D002110:Caffeine; D013806:Theophylline