Masahiko Obayashi

Determination of concentrations of flecainide in human serum by high-performance liquid chromatography on a fluorocarbon-bonded silica gel column

An optimized method for the determination of flecainide in serum is presented. Extraction using a solid-phase C18 column and chromatography on a stabilized fluorocarbon-bonded silica gel column effectively separate flecainide from an internal standard (a positional isomer of flecainide). The HPLC apparatus and conditions were as follows: analytical column, Fluofix 120N; sample solvent, 20 microl; column temperature, 40 degrees C; detector, Shimadzu RF-5000 fluorescence spectrophotometer (excitation wavelength = 300 nm, emission wavelength = 370 nm); mobile phase, 0.06% phosphoric acid containing 0.1% tetra-n-butyl ammonium bromide-acetonitrile (75:25, v/v); flow-rate, 1.0 ml/min. The standard curves for flecainide were linear in the concentration range examined (10-2000 ng/ml). The regression equation was y = 0.08+0.0078x (r = 0.9998). The minimum detectable amount of flecainide was approximately 5 ng/ml. In the within-day study, the precision coefficients of variation were 2.66, 2.18, 2.54, 2.72, 2.88, 2.24, and 3.29% for the 10, 50, 100, 200, 500, 1000, and 1500 ng/ml standards, respectively. The absolute recovery rates of flecainide at each concentrations were 94-100%. The method described provides analytical sensitivity, specificity and reproducibility suitable for both biomedical research and therapeutic drug monitoring.

Inhibitory activities of selected Kampo formulations on human aldose reductase

BackgroundDiabetes complications include various symptoms such as diabetic neuropathy and cognitive disorders. Aldose reductase (AR) is the rate-limiting enzyme of the polyol pathway and is one of the causal factors of diabetes complications. In this study, the bioactivities of eight selected Kampo formulations that are currently in clinical use for diabetes complications were assessed using human AR (hAR) inhibitory activity as the primary parameter to explore the possibilities of novel clinical applications of these formulations in the treatment of diabetes complications.MethodsThe hAR inhibitory activities of four Kampo formulations that are clinically used for diabetic neuropathy, four Kampo formulations that are used for cognitive disorders, and a total of 21 component crude drugs were measured. Furthermore, the hAR inhibitory activity of Glycyrrhizae Radix preparata was measured to determine the effect of frying, which is one of the specific processing of Glycyrrhizae Radix. hAR inhibitory activity was determined by measuring the rate of decline in the absorbance of NAPH at 340 nm using 0.5 mM NADPH, 10 mM D,L-glyceraldehyde, and 3.6 mU/mL hAR in phosphate buffer solution (0.2 M, pH 6.2).ResultsAll of the Kampo formulations exhibited significant hAR inhibitory activity; Chotosan exhibited particularly strong activity. Among the 21 crude drugs tested, adequate inhibitory activities were found for the following, in descending order of activity: Glycyrrhizae Radix > Paeoniae Radix > Chrysanthemi Flos > Cinnamomi Cortex > Phellodendri Cortex > Uncariae Uncis cum Ramulus > Bupleuri Radix. Glycyrrhizae Radix preparata exhibited an inhibitory activity that was nearly identical to that of Glycyrrhizae Radix.ConclusionsDespite their seemingly different treatment objectives, all of the Kampo formulations that are clinically used for diabetes complications demonstrated significant hAR inhibitory activity. This activity might underlie the characteristic multi-target effects of Kampo formulations. Although the overall effect of a Kampo formulation is certainly difficult to evaluate based on specific herbal medications or components, the approach as taken in this study might nonetheless contribute to further advancement in the development of new drugs via the review of proper usage and re-examination of the chemical compounds from a new perspective.

Clinical Usefulness of Losartan, an Angiotensin II Receptor Antagonist with a Uricosuric Effect, and the Influence of Aspirin on the Effect in Hypertensive Patients with Hyperuricemia

Losartan, an angiotensin II receptor antagonist, has been reported to decrease the serum uric acid (SUA) level and increase the urinary excretion of uric acid. This action might be beneficial in hypertensive patients, who frequently suffer from hyperuricemia and sometimes gout. The aims of this study were to evaluate the uricosuric effect of losartan on hypertensive patients with hyperuricemia (SUA>7mg/dL), identify factors that influence the uricosuric effect of losartan, and determine whether or not medication of hyperuricemia with other drugs is necessary.A total of 28 hypertensive patients with hyperuricemia were studied retrospectively (no medication for hyperuricemia). Aspirin was found to be a factor that influences the uricosuric effect of losartan (p= 0.088). In hypertensive patients with hyperuricemia treated with aspirin medication (N = 7), losartan did not significantly decrease the SUA levels from 8.56 ± 0.66 to 8. 29 ± 0. 40mg/dL. Moreover, none of the patients had their SUA controlled of a normal level by losartan. In hypertensive patients with mild hyperuricemia (7.0≤SUA<8.0, without aspirin medication, N=12), losartan decreased the SUA level significantly from 7.35±0.08 to 6.85±0.32mg/dL. In five of the 12 patients, losartan controlled SUA at a normal level. Therefore, when losartan is prescribed to these patients, the treatment of mild hyperuricemia may not require the use of other drugs. In hypertensive patients with severe hyperuricemia (8.0≤SUA, without aspirin medication, N=9), losartan decreased the SUA level significantly from 9.55±0.57 to 8.21±0.35mg/dL. However, none of the patients had their SUA controlled at a normal level by losartan. Although the decrease of SUA level by losartan can be expected in these patients, the control of SUA at a normal level could not be expected. Therefore, the treatment of hyperuricemia with other drugs is considered to be required for these patients. Losartan may be a useful therapeutic drug to control the blood pressure and SUA levels in hypertensive patients with mild hyperuricemia