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The assay and absorption kinetics of oral theophylline−7‐acetic acid in the human
Author(s) -
Sved S.,
McGilveray I. J.,
Beaudoin N.
Publication year - 1981
Publication title -
biopharmaceutics and drug disposition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.419
H-Index - 58
eISSN - 1099-081X
pISSN - 0142-2782
DOI - 10.1002/bdd.2510020210
Subject(s) - chemistry , chromatography , theophylline , acetic acid , chloroform , dichloromethane , ethyl acetate , bioavailability , butanol , pharmacokinetics , aqueous solution , ethanol , urine , absorption (acoustics) , solvent , pharmacology , organic chemistry , biochemistry , medicine , physics , acoustics
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 moll −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.