PubMed · 10997110
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2000. Caffeine caution.. https://pubmed.ncbi.nlm.nih.gov/10997110/
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An automated reversed-phase high-performance liquid chromatographic (RP-HPLC) method, using a linear gradient elution, is described for the simultaneous analysis of caffeine and metabolites according to their elution order: 7-methyluric acid, 1-methyluric acid, 7-methylxanthine, 3-methylxanthine, 1-methylxanthine, 1,3-dimethyluric acid, theobromine, 1,7-dimethyluric acid, paraxanthine and theophylline. The analytical column, an MZ Kromasil C4, 250 x 4 mm, 5 microm, was operated at ambient temperature with back pressure values of 80-110 kg/cm2. The mobile phase consisted of an acetate buffer (pH 3.5)-methanol (97:3, v/v) changing to 80:20 v/v in 20 min time, delivered at a flow-rate of 1 ml/min. Paracetamol was used as internal standard at a concentration of 6.18 ng/microl. Detection was performed with a variable wavelength UV-visible detector at 275 nm, resulting in detection limits of 0.3 ng per 10-microl injection, while linearity held up to 8 ng/microl for most of analytes, except for paraxanthine and theophylline, for which it was 12 ng/microl and for caffeine for which it was 20 ng/microl. The statistical evaluation of the method was examined performing intra-day (n=6) and inter-day calibration (n=7) and was found to be satisfactory, with high accuracy and precision results. High extraction recoveries from biological matrices: blood serum and urine ranging from 84.6 to 103.0%, were achieved using Nexus SPE cartridges with hydrophilic and lipophilic properties and methanol-acetate buffer (pH 3.5) (50:50, v/v) as eluent, requiring small volumes, 40 microl of blood serum and 100 microl of urine.
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BACKGROUND: Caffeine elimination and monitoring of its metabolites after a single peroral administration in used to evaluate liver metabolic function. The aim of the study was to use the paraxanthine/caffeine ratio in saliva to evaluate liver function in patients with liver cirrhosis. Results were correlated with various procedures evaluating the elimination rate of caffeine. METHODS AND RESULTS: The study group consisted of 7 patients with compensated liver cirrhosis and 10 healthy volunteers, all individuals were given a single 280 mg dose of caffeine perorally. Concentration of salivary caffeine was determined in each person with high performance liquid chromatography after 4, 6, 8 and 12 hours after application. The paraxanthine/caffeine ratio was evaluated at the 6-hour interval. Estimated clearance (CL), half-life (t1/2) and volume of distribution (Vd) were calculated from 2 or 4 concentrations of the drug. The metabolic ratio of the patients (x = 0.15 +/- 0.07) was significantly lower then the control group (x = 0.55 +/- 0.29). Using a four-point procedure we acquired the following values: patients--CL 2.39 +/- 2.36 l/h, t1/2 = 90.18 +/- 168.44 h; healthy volunteers--CL = 8.10 +/- 4.58 l/h, t1/2 = 8.60 +/- 4.12 h (p < 0.05). Statistically significant correlation was found between the metabolic ratio and CL value (rs = 0.83) or between half-life (rs = -0.72). Similar results were also obtained using the two-point method. CONCLUSION: In patients with liver cirrhosis we found significantly lower paraxanthine/caffeine ratio which correlates with lowered elimination of caffeine. Its evaluation enables non-invasive assessment of liver metabolic function from a single sample of saliva.