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Biomedical subjects

W L Chiou

Publications and source records attributed to W L Chiou.

At least 127 records · Page 7Linked to original sources
PubMed1979

Triexponential disposition pharmacokinetics of gentamicin in rabbits.

Using a sensitive high-pressure liquid chromatographic method for the determination of gentamicin, plasma-level profiles of gentamicin were found to fit to a triexponential equation in 3 out of 4 rabbits studied after bolus intravenous administration by the application of the Minimum Akaike's Information Criterion Estimation (MAICE) method. This is different from the monoexponential or biexponential decay of gentamicin often reported in humans. Volumes of distribution of central compartment and at the steady-state in rabbits were similar to those reported in humans. Extensive distribution and tissue binding of gentamicin in rabbits were indicated by their high Vdarea, about 3.9 l/kg. It is proposed that rabbits may serve as a useful model for studying the mechanism and prediction of renal toxicity of gentamicin in patients.

Animals↗
PubMed1978

Simple, rapid and micro high-pressure liquid chromatographic method for the simultaneous determination of tolbutamide and carboxy tolbutamide in plasma.

A rapid high-pressure liquid chromatographic (HPLC) assay is described for the quantitative analysis of tolbutamide and its major metabolite, carboxy tolbutamide in plasma. An aliquot (25--100 microliter) of plasma was prepared for chromatography by deproteinization as follows. One volume of plasma and 2.5 volumes of acetonitrile were vortex mixed for a few seconds and then centrifuged for approx. 1 min. A 50-microliter sample of the clear supernatant was injected into the chromatograph. A mu Bondapak C18 reversed-phase column was used with a mobile phase acetonitrile--0.05% phosphoric acid (45:55) at a flow-rate of 1.5 ml/min. The column effluent was monitored by a variable-wavelength UV detector set at 200 nm. Tolbutamide and its metabolite had retention times of 5.75 and 3.25 min, respectively. The procedure yuelds reproducible results with sensitivity adequate for routine clinical monitoring of plasma levels or for single-dose pharmacokinetic studies. A number of commonly used drugs do not interfere with the method. A single plasma sample can be analyzed in approx. 9 or 10 min.

Animals↗
PubMed1978

High-pressure liquid chromatographic method for the simultaneous quantitative analysis of propranolol and 4-hydroxypropranolol in plasma.

A simple and rapid high-pressure liquid chromatographic procedure is reported for the simultaneous quantitative determination of propranolol and 4-hydroxypropranolol in plasma. Following an extraction the samples are chromatographed on a reversed-phase column and the components in the column effluent are detected by fluorescence monitoring. Using 1-ml plasma samples propranolol and 4-hydroxypropranolol concentrations at least as low as 1 ng/ml and 5 ng/ml, respectively, can be quantitated. The reproducibility of the method is satisfactory and no interference from endogenous plasma components or other drugs has been observed. A single plasma sample can be analyzed in approximately 20 min.

Chromatography, High Pressure Liquid↗
PubMed1978

Simple, rapid and micro high-pressure liquid chromatographic determination of endogenous "true" creatinine in plasma, serum, and urine.

Previously published methods for endogenous creatinine levels in plasma, serum, or urine lack specificity or are subject to interferences from endogenous or exogenous substances. The developed simple, rapid, and specific high-pressure liquid chromatographic method includes the novel deproteinization and extraction of 1 volume of plasma or serum with 2.5 volumes of acetonitrile and also of 1 volume of urine with 40 volumes of a 20% water-80% acetonitrile solution. An aliquot of the supernate is then injected directly into the chromatograph. A cation-exchange column and acidified (0.02% of 85% phosphoric acid) 0.1 M ammonium phosphate solution as the mobile phase, with a flow rate of 2 ml/min, were used. Creatinine, with a retention time of 3.8 min, was monitored via its UV absorption at 215 nm. Both peak heigh and integrated area methods of quantitation yielded the same results. Several methods were employed to show that the "suspected" creatinine peak from plasma samples was due entirely to the "true" creatinine. No interference was found in samples obtained from normal and renal patients. The day-to-day variation in the detector response was small. Each assay requires only about 5 min for completion. Ten microliters of plasma or serum or 1 microliter of urine is sufficient for analysis.

Adult↗
PubMed1978

Simple and rapid high-pressure liquid chromatographic simultaneous determination of aspirin, salicylic acid, and salicyluric acid in plasma.

A rapid and sensitive high-pressure liquid chromatographic assay was developed for aspirin, salicylic acid, and salicyluric acid in plasma. The procedure involves the solvent extraction of these compounds from plasma and separation using a reversed-phase column eluted by acidified aqueous acetonitrile. Small quantitites of aspirin can be assayed directly in the presence of a large quantity of salicylic acid. The assay is also free from blank interference.

Aspirin↗
PubMed1978

Simple, rapid, and micro high-pressure liquid chromatographic determination of plasma griseofulvin levels.

A rapid high-pressure liquid chromatographic assay is described for the quantitative determination of griseofulvin in plasma. An aliquot (25--10 microliter) of plasma was deproteinized by a simple procedure involving the addition of 2.5 volumes of acetonitrile, vortex mixing for a few seconds, and centrifugation for 1 min. The clear supernate, 50 microliter, was injected into the high-pressure liquid chromatograph. A reversed-phase column was used with a mobile phase of distilled water-acetonitrile (1:1) at a flow rate of 2 ml/min and was operated at ambient temperature. A fluorescent detector with an excitation wavelength of 260 nm was employed to monitor the column effluent. Griseofulvin had a retention time of 3.8 min. This procedure yields reproducible results with high sensitivity; plasma concentrations as low as 50 ng/ml can be measured. Several commonly used drugs do not interfere. Analysis of plasma samples collected from a rabbit injected with griseofulvin indicated that the procedure is suitable for pharmacokinetic studies and clinical monitoring of plasma concentrations in patients. Assay turnaround time is less than 6 min. For clinical monitoring of plasma griseofulvin concentrations, a sample volume as small as 10 microliter can be used.

Animals↗
PubMed1978

Rapid and micro high-pressure liquid chromatographic method for simultaneous determination of procainamide and N-acetylprocainamide in plasma.

A rapid and simple high-pressure liquid chromatographic method was developed for the simultaneous determination of plasma levels of procainamide and its major metabolite, N-acetonitrile, and the supernate was chromatographed on a cation-exchange column. The assay can be carried out on as little as 20 microliter of plasma and requires only about 7 min for each sample. No interference was found in plasma samples from cardiac patients receiving procainamide. This method is simple, fast, and useful for routine therapeutic monitoring and for pharmacokinetic studies procainamide and its metabolite.

Acetylation↗
PubMed1978

Rapid and micro high-pressure liquid chromatographic determination of chloramphenicol in plasma.

A high-pressure liquid chromatographic method was developed for chloramphenicol in plasma. Plasma samples were deproteinized with 2.5 volumes of acetonitrile, and the supernates were chromatographed on a reversed-phase column, using acidified ethanol-water as the mobile phase and UV spectrophotometry for detection. The sensitivity for accurate quantitation of chloramphenicol was about 2.5 microgram/ml in plasma, and concentrations as low as 0.5 microgram/ml could be detected. Only about 8 min is needed for each sample. This method is specific, rapid, and sufficiently sensitive and may be useful for clinical monitoring.

Animals↗
PubMed1978

Rapid and micro high-pressure liquid chromatographic determination of plasma phenytoin levels.

A rapid and simple high-pressure liquid chromatographic microanalytical method was developed for the determination of clinically encountered plasma phenytoin levels. This method is accurate down to about 1 microgram of phenytoin/ml of plasma and requires as little as 10 microliter of sample. Total analysis time is about 10 min. The method involves deproteinizing with acetonitrile followed by monitoring the deproteinized sample at 254 nm. Phenytoin's primary metabolite in humans, 5-(p-hydroxyphenyl)-5-phenylhydantoin, also can be quantitated when present in moderately high clinically encountered concentrations. Plasma profiles of phenytoin and its metabolite were followed with time after an intravenous bolus injection to a rabbit.

Animals↗
PubMed1978

Critical evaluation of the potential error in pharmacokinetic studies of using the linear trapezoidal rule method for the calculation of the area under the plasma level--time curve.

The linear trapezoidal rule method is commonly used for the estimation of the area under the plasma level-time curve. Error analyses are performed when the method is used in first-order absorption and first-order elimination kinetics in the one-compartment system. It is found that significant underestimations and overestimations in area during the absorption phase and postabsorption phase, respectively, can occur when the method is improperly used. During the exponential postabsorption phase the relative error is only a function of the ratio (n) of the time interval over the half-life of the two plasma data points in the interval. The error from the linear trapezoidal rule method at n = 0.5 is about 1%. The error increases to 15.5% and 57.1% when n is increased to 2 and 4, respectively. It is recommended that for most absorption studies the linear trapezoidal method be used for prepeak and plateau plasma data and the logarithmic trapezoidal method for postpeak plasma data.

Half-Life↗
PubMed1978

High-performance liquid-chromatographic determination theophylline in plasma.

A high-performance liquid-chromatographic method is reported for monitoring theophylline in plasma. Samples are deproteinized with 2.5 volumes of acetonitrile and the supernates chromatographed on a reversed-phase column. Absorption at 275 nm is monitored. One can accurately measure 1.5 mg of theophylline per liter, in as little as 10 microliter of plasma, and only about 7 min is required per sample. No interference was found in plasma samples from asthmatic patients. This method is particularly useful for routine therapeutic monitoring of both pediatric and adult patients.

Chromatography, High Pressure Liquid↗