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Biomedical subjects

R D Hossie

Publications and source records attributed to R D Hossie.

9 recordsLinked to original sources
PubMed1980

Quantitation of acetazolamide in plasma by high-performance liquid chromatography.

A method for estimating acetazolamide concentrations in human plasma is described. Buffered plasma (pH 4.8) containing chlorothiazide as an internal standard is extracted twice with ethyl acetate. The extract is evaporated, redissolved, and chromatographed on silica gel with hexane-chloroform-methanol-acetic acid (65:25:10:0.25) as the mobile phase. The extraction efficiencies were greater than 90%, the coefficients of variation at 1 and 30 micrograms/ml of plasma were 3.5 and 2.0%, respectively, and the calibration curves were linear and had an intercept of essentially zero. The suitability of the method for pharmacokinetic studies was verified in a normal volunteer dosed with 250-mg (solution) and 500-mg (sustained-release tablet) acetazolamide formulations.

Acetazolamide↗
PubMed1977

High performance liquid chromatographic and mass spectrometric identification of dimethylxanthine metabolites of caffeine in human plasma.

High performance liquid chromatography and mass spectrometry were used to isolate and identify theophylline, theobromine and 1,7-dimethylxanthine (paraxanthine) in plasma of human volunteers following administration of 300 mg caffeine to methylxanthine-free volunteers. Plasma from these subjects was extracted and the dimethylxanthines were separated from each other and caffeine by high performance liquid chromatography. The effluents at the chromatographic peaks corresponding to the dimethylxanthine metabolites were collected, rechromatographed in a second system and the dried residues were subjected to mass spectrometry. By comparison of their retention times and mass spectra with those of authentic compounds, theophylline, theobromine and paraxanthine were positively identified as metabolic products of caffeine.

Caffeine↗
PubMed1976

The human metabolism of caffeine to theophylline.

Theophylline peak plasma concentration of over 170 ng/ml average was observed when 300 mg of caffeine, equivalent to 2-3 cups of coffee, was administered to humans. This peak level was not observed until at least 7 hr post administration. Accumulation of caffeine, with its subsequent metabolism to theophylline, in patients, who consume average quantities of caffeine-containing beverages relative to those patients who avoid such drinks could interfere with bioavailability studies in normal volunteers. However, it may account for only a small portion of the variable clinical effects associated with aminophylline administration.

Allopurinol↗