An HPLC Method for the Determination of Theophylline and Its Metabolites in Serum and Urine

Theophylline-7β-d-Ribofuranoside (Theonosine), a New Theophylline Metabolite Generated in Human and Animal Lung Tissue

While assessing the ability of mammalian lung tissue to metabolize theophylline, a new metabolite was isolated and characterized. The metabolite was produced by the microsomal fraction of lungs from several species, including rat, rabbit, dog, pig, sheep and human tissue. Metabolite production was blocked by boiling the microsomal tissue. This new metabolite, theophylline-7β-d-ribofuranoside (theonosine), was confirmed by several spectral methods and by comparison to an authentic synthetic compound. Tissue studies from rats, rabbits, dogs, and humans for cofactor involvement demonstrated an absolute requirement for NADP and enhanced metabolite production in the presence of magnesium ion. It remains to be demonstrated whether theonosine may contribute to the known pharmacological effects of theophylline.

An isocratic high-performance liquid chromatographic system for simultaneous determination of theophylline and its major metabolites in human urine

A simple and highly selective isocratic high-performance liquid chromatography method is presented for the simultaneous determination of theophylline and its major metabolites in human urine using beta-hydroxyethyl theophylline as an internal standard. The method utilizes direct injection of diluted urine samples followed by separation and quantitation by reversed-phase isocratic elution and ultraviolet detection. The assay is accurate and reproducible with a sensitivity of 1 microgram ml-1 for theophylline and 0.5 micrograms ml-1 for its metabolites. The assay was employed for the analysis of theophylline and its major metabolites in urine following the oral administration of theophylline to four healthy volunteers.

High-performance liquid chromatographic assay for theophylline and its major metabolites in human urine

A highly selective automated high-performance liquid chromatographic (HPLC) method has been developed for the assay of theophylline and its major metabolites in urine. The method involves direct injection of urine on to a reversed-phase column, followed by gradient elution and ultraviolet detection. Quantitation is achieved by the peak-height ratio method with reference to an internal standard, 8-chlorotheophylline. The assay is accurate and reproducible, with a sensitivity of 1 microgram/ml in urine. In order to confirm its accuracy, theophylline and its major metabolites in urine were quantified after HPLC separation by both peak-height ratio of ultraviolet absorbance and liquid scintillation spectrometry after oral administration of [14C]theophylline to a human volunteer. The assay was also applied to the analysis of theophylline and its major metabolites in urine following the oral administration of theophylline to three healthy volunteers.

Determination of theophylline and its metabolites in plasma and urine by reversed-phase liquid chromatography using an amine modifier

A high-performance liquid chromatographic method for the determination of the concentrations of theophylline and its metabolites in plasma and urine samples is presented. The method uses the decylammonium ion, an N-alkylammonium modifier, and makes it possible to separate theophylline and its metabolites from other uric acid or xanthine derivatives, especially 1,7-dimethylxanthine, a metabolite of caffeine. The plasma and urine purification procedure is convenient, rapid and reproducible, and it can be used to determine low plasma and urine concentrations.

Ion-pair high-performance liquid chromatographic procedure for the quantitative analysis of theophylline in serum samples

An ion-pair chromatographic system is described for the separation of theophylline and related xanthines from serum samples. The mobile phase consisted of 0.02 M tetrabutylammonium ion and 0.015 M Tris buffer in water-acetonitrile-methanol (93:3.5:3.5, v/v/v) at a precisely controlled pH (7.50 +/- 0.02, adjusted with hydrochloric acid). The flow-rate was 1.2 ml/min through a 15 cm X 4.6 mm I.D., 5-micron reversed-phase column (Ultrasphere C18 ion pair). Xanthines were extracted from serum (100 microliter) with 1 ml of acidified chloroform-isopropanol (95:5, v/v). After reconstitution in 200 microliter of mobile phase, the extracted xanthines, including theophylline, caffeine, theobromine and 1.7-dimethylxanthine, were baseline-resolved in less than 15 min. The method correlates well with a common clinical immunoassay for theophylline (EMIT Syva, r2 = 0.999) and yields excellent recovery and precision (98-101% and better than 2% at therapeutic levels, respectively). In addition, the use of the ion-pair chromatography mode eliminates many of the interferences noted in the published literature for the common reversed-phase separations of theophylline.

A new simplified assay for the quantitation of theophylline and its major metabolites in urine by high-performance liquid chromatography

A high-performance liquid chromatographic technique is presented for the simultaneous determination of theophylline, 3-methylxanthine, 1-methyluric acid, 1,3-dimethyluric acid, and caffeine in urine using beta-hydroxyethyl theophylline (BHET) as an internal standard. Following centrifugation of the sample, 2 mL of urine was placed onto a Sep-Pak C18 cartridge (Waters Associates, Milford, MA, USA) that was prepared with 5 mL of methanol followed by 10 mL of distilled water. The compounds were eluted with 2.5 mL of a methanol:water (50:50) mixture. An aliquot of the filtered urine sample (100 microL) was added to 40 microL of an internal standard solution (BHET; 100 micrograms/mL). Distilled water (60 microL) was added to yield a volume of 200 microL. The mixture was vortexed and centrifuged, and 100 microL was injected onto a C8 column maintained at 55 degrees C. Inter- and intraday variability of the assay for all compounds was less than 5.7%. Sensitivity ranged from 0.10 microgram/mL for caffeine to 0.68 microgram/mL for 1-methyluric acid. Drugs commonly coadministered with theophylline did not interfere with the assay.

New simplified microassay for the quantitation of theophylline and its major metabolites in serum by high-performance liquid chromatography

A high-performance liquid chromatographic technique is presented for simultaneous determination of theophylline, 3-methylxanthine, 1-methyluric acid, 1,3-dimethyluric acid and caffeine in serum using beta-hydroxyethyltheophylline (BHET) as an internal standard. An aliquot of a serum sample (100 microliters) was added to 40 microliters of an internal standard solution (BHET; 100 micrograms/ml) and vortexed. A 20% trichloroacetic acid solution (60 microliters) was then added; the mixture was vortexed, centrifuged and 100 microliters were injected onto a C8 column maintained at 45 degrees C. Inter- and intra-day variability of the assay for all compounds was less than 4.3%. Sensitivity ranged from 10 ng/ml for 1-methyluric acid to 25 ng/ml for theophylline. Drugs commonly coadministered with theophylline did not interfere with the assay.