title: The assay and absorption kinetics of oral theophylline-7-acetic acid in the human.
abstract: A sensitive and specific method for the estimation of theophylline-7-acetic acid in plasma by high performance liquid chromatography is described. Acidified plasma is extracted with chloroform-n-butanol (85: 15), back extracted with phosphate buffer (0.5 mmol-1, pH 6.5), and finally the acidified aqueous phase extracted again with chloroform-butanol. After evaporation of the extract the residue is redissolved in the chromatographic mobile phase (hexane-dichloromethane-ethanol-acetic acid, 10 : 86 : 3 : 1) and chromatographed on silica gel. The method was used to follow the plasma theophylline-7-acetic acid concentrations in two volunteers after single oral doses of 1.0 g of the drug. The results confirm previous reports, based on urine data and on plasma data following intravenous administration, that the drug is poorly absorbed (apparent bioavailability of 1 and 2 per cent), rapidly eliminated (half-life of 1.0 and 2.4 h) and not converted to theophylline.
mesh_terms: D001682:Biological Availability; D006801:Humans; D007408:Intestinal Absorption; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D012995:Solubility; D013607:Tablets; D013806:Theophylline / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood / Q000378:metabolism
chemical_list: D013607:Tablets; D013806:Theophylline; C019140:acefylline