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Biomedical subjects

I Kanfer

Publications and source records attributed to I Kanfer.

At least 37 records · Page 2Linked to original sources
PubMed1995

Sensitive high-performance liquid chromatographic determination of cyclizine and its demethylated metabolite, norcyclizine, in biological fluids using coulometric detection.

An accurate, sensitive, selective and reproducible high-performance liquid chromatographic method with coulometric detection for the determination of cyclizine and its inactive demethylated metabolite, norcyclizine, in biological fluids has been developed. The drugs were separated using a custom packed reversed-phase C18 analytical column and phosphate buffer (0.05 M, pH 3)-acetonitrile (7:3) as mobile phase. The dual electrode coulometric detector was operated in the "oxidative-screen" mode with the upstream electrode (detector 1) set at 0.55 V and the downstream electrode (detector 2) set at 0.90 V. Serum and urine samples were prepared for analysis by solid-phase extraction, followed by a simple phase-separation step. The limit of quantitation was 1 ng/ml for both cyclizine and norcyclizine in serum and urine.

Chromatography, High Pressure Liquid↗
PubMed1990

Steady state pharmacokinetics and dose-proportionality of phenylpropanolamine in healthy subjects.

The pharmacokinetics of phenylpropanolamine (PPA) were studied in five healthy male volunteers after single oral doses of 25, 50 and 100 mg of the drug as well as at steady state after seven, 4-hourly doses of PPA. The peak serum concentrations and AUC infinity values increased linearly with an increase in dose, whereas the time to reach peak serum concentrations did not vary significantly between doses. The half-life remained relatively constant with an increase in dose (t1/2 = 3.8 to 4.3 hours), as did renal clearance (ClR = 0.41 to 0.44 l/kg/h). The percentage of unchanged PPA excreted in the urine over a 14 hour period was 64%, 63% and 73% for the 25, 50 and 100 mg doses, respectively. The pharmacokinetics of PPA were found to be linear in the dosage range 25 to 100 mg. Steady state serum concentrations were significantly higher than single dose concentrations, with the mean peak serum concentration increasing from 113 ng/ml after a single dose to 183 ng/ml at steady state. The time at which these were attained decreased from 1.47 hours after a single dose to 0.73 hours at steady state. Both clearance and volume of distribution were significantly different after a single dose compared to steady state (P less than 0.05), whereas no significant differences were found between the other parameters.

Administration, Oral↗
PubMed1990

Serum concentrations of phenylpropanolamine and associated effects on blood pressure in normotensive subjects: a pilot-study.

This study was undertaken to investigate the effects of racemic phenylpropanolamine (PPA) on blood pressure (BP) in normotensive human subjects following the administration of three different dosages of PPA (25 mg, 50 mg and 100 mg) as single doses and to determine whether any relationship existed between the serum concentrations of PPA and its possible effects on BP. Blood was sampled and BP measured at specified times. Phenylpropanolamine was determined by HPLC with UV detection. No significant changes in BP occurred following the 25 mg dose (5 +/- 7/6 +/- 6 mm Hg), whereas statistically significant changes were found after the two higher doses of 50 mg (26 +/- 16/12 +/- 13 mm Hg) and 100 mg (30 +/- 13/15 +/- 8 mm Hg). Increases in systolic pressure following the 50 mg and 100 mg doses appeared to show a better correlation with peak serum concentrations of PPA than did diastolic effects. Although serum concentrations of PPA increased linearly with increasing dose, no clear-cut correlation could be found between serum concentrations and BP effects. The pressor effects, however, became more noticeable following the 50 mg dose and were markedly increased following the 100 mg dose. Side-effects which were reported were relatively minor even at the higher doses.

Adult↗
PubMed1989

Variability in the absorption and disposition of erythromycin estolate in humans.

The inter- and intrapersonal variability in the absorption and disposition of erythromycin estolate in humans was assessed by comparing total erythromycin serum concentrations in five subjects who each received a single erythromycin estolate tablet on three separate occasions under identical experimental conditions. Coefficients of variation for the pharmacokinetic parameters Cmax, Tmax, AUC0-12, MRT, and t1/2 were of a similar magnitude when calculated between subjects in any one administration phase or between phases. In addition, serum concentrations of both erythromycin base (active component) and erythromycin propionate were selectively determined in the same subjects only during the final two phases of the study. Comparison of AUC0-12 values showed that the percentage of the total area (base and ester components) present as erythromycin base remained relatively constant between administrations (mean values of 14.5 and 11.2%), with low coefficients of variation between subjects (10.8 and 11.6%). Discrepancy value calculations revealed that the variability in serum concentration-time profiles between the three phases of the study fell into the "small"-to-"moderate" classification. From these data it is apparent that intrapersonal variations in the absorption and disposition of erythromycin estolate are of a similar magnitude to interpersonal variations and should be borne in mind in the design and interpretation of comparative bioavailability studies involving similar formulations of this compound. The relative proportions of erythromycin base and propionate did, however, remain fairly constant both between treatments and between subjects.

Adult↗
PubMed1988

High-performance liquid chromatographic analysis of josamycin in serum and urine.

A high-performance liquid chromatographic assay for the analysis of josamycin in human serum and urine is presented. The assay involves a simple solid-phase extraction procedure coupled with a phase separation step, separation on a reversed-phase C18 column with UV detection by a multi-wavelength programmable detector. The mobile phase was acetonitrile-0.015 M phosphate buffer, pH 6.0 (5:2) at a flow-rate of 1.2 ml/min. The column temperature was maintained at 35 degrees C. Linear calibration curves over the concentration ranges 0.1-2.0 mg/l (serum) and 0.5-5 mg/l (urine) were obtained with correlation coefficients of 0.9983 and 1.0000, respectively. The relative standard deviations of five replicate samples at the upper and lower limits of each calibration curve were below 7%. The recoveries at the upper and lower ends of the calibration range for serum were 77% and 70%, respectively, and those for urine were 76% and 80%, respectively.

Chemical Phenomena↗
PubMed1988

High-performance liquid chromatography of erythromycin propionyl ester and erythromycin base in biological fluids.

The simultaneous determination of erythromycin propionate and erythromycin base in serum and urine by high-performance liquid chromatography using oleandomycin as internal standard is described. The separation was achieved on a reversed-phase C18 column employing acetonitrile-0.05 M phosphate buffer (65:35), adjusted to pH 7.0, as the mobile phase with coulometric detection. Hydrolysis of the ester during blood sample collection was minimised by immediate high-speed centrifugation of collected blood samples, followed by separation and immediate freezing of the serum fraction. A solid-phase extraction procedure, combined with a simple phase-separation step was used prior to chromatographic analysis. The method has the necessary precision, sensitivity and accuracy to allow the simultaneous determination of both components in serum and urine following a single 500-mg oral dose of erythromycin estolate.

Chromatography, High Pressure Liquid↗
PubMed1988

Potency ranking of two new topical corticosteroid creams containing 0.1% desonide or 0.05% halometasone utilising the human skin blanching assay.

The human blanching assay was used to assess the potency of two new proprietary corticosteroid creams. The blanching abilities of 0.1% desonide cream and 0.05% halometasone cream were evaluated relative to the blanching elicited by 0.05% clobetasol 17-propionate cream, 0.1% betamethasone 17-valerate cream and 0.05% clobetasone 17-butyrate cream. The results of the trial indicated that the 0.1% desonide cream falls into the potent group of topical corticosteroid preparations and the 0.05% halometasone cream falls into the moderately potent group.

Administration, Topical↗
PubMed1986

High-performance liquid chromatographic analysis of oleandomycin in serum and urine.

The determination of oleandomycin in serum and urine by high-performance liquid chromatography using erythromycin as internal standard is described. The separation was achieved on a reversed-phase C18 column employing acetonitrile-0.05 M phosphate buffer (30:70), adjusted to pH 7.0, as the mobile phase with UV detection at 200 nm. A solid-phase extraction procedure, combined with a simple phase-separation step was used prior to chromatographic analysis. Linear calibration curves were obtained in the concentration ranges 0.25-5.0 micrograms/ml (serum) and 1.0-25.0 micrograms/ml (urine). Precise quantitative analysis has been achieved at these levels with relative standard deviations of less than 5%.

Chromatography, High Pressure Liquid↗
PubMed1985

Determination of erythromycin in serum and urine by high-performance liquid chromatography with ultraviolet detection.

A high-performance liquid chromatographic analysis of erythromycin in human serum and urine with UV detection at 200 nm is presented. The method involves a solid-phase extraction procedure followed by a simple phase separation step and chromatography on a reversed-phase column. The method has sensitivity limits of 0.25 and 1.0 micrograms/mL in serum and urine, respectively, and is sufficiently sensitive to monitor concentrations of erythromycin in human serum and urine after the administration of a single 500-mg erythromycin stearate tablet.

Chromatography, High Pressure Liquid↗
PubMed1984

Determination of picogram nitroglycerin plasma concentrations using capillary gas chromatography with on-column injection.

A specific, sensitive, and precise capillary gas chromatographic (GC) assay capable of analyzing picogram concentrations of nitroglycerin in human plasma was developed. The analytical procedure involves a double extraction of 1 mL of plasma with pentane, after the addition of internal standard (1 ng of 2,6-dinitrotoluene), followed by evaporation and reconstitution in 50 microL of heptane. The extract (1 microL) was injected onto a capillary column using the on-column injection technique. The GC oven temperature was programmed from 120 degrees C to 180 degrees C at a rate of 5 degrees C/min. The oven temperature was then programmed to 250 degrees C and was maintained for 10 min. The nitroglycerin and internal standard retention times were 8.6 and 11.4 min, respectively. The position of the end of the capillary column inside the detector is a critical determinant of sensitivity: the column exit must be positioned such that nitroglycerin adsorption to the detector is minimized (i.e., sensitivity maximized). The assay limit of quantitation was 25 pg/mL (CV = 7.6%) using 1 mL of plasma. This GC assay, specific for nitroglycerin in the presence of its metabolites, isosorbide dinitrate, and several other drugs, may be used to quantitate plasma levels obtained after therapeutic nitroglycerin doses.

Chromatography, Gas↗
PubMed1983

Determination of phenylpropanolamine in serum and urine by high-performance liquid chromatography.

A high-performance liquid chromatographic analysis of phenylpropanolamine in human serum and urine without prior derivatization is presented. Using direct UV detection the method is sufficiently sensitive to detect 25 ng of drug/ml of serum or urine; the coefficients of variation at 25 ng/ml and 500 ng/ml were 5. 16 and 2.12, respectively, in serum. The method involves serum and urine extraction at a basic pH with chloroform, a single back-extraction, and chromatography on a reverse-phrase column. Serum and urine data following administration of a single 150-mg sustained-release tablet of phenylpropanolamine hydrochloride in six healthy volunteers demonstrates the suitability of the analytical method.

Biological Availability↗
PubMed1981

Simultaneous determination of trimethoprim, sulphamethoxazole and N4-acetylsulphamethoxazole in serum and urine by high-performance liquid chromatography.

The simultaneous determination of trimethoprim, sulphamethoxazole and N4-acetyl-sulphamethoxazole in serum and urine by high-performance liquid chromatography using sulphafurazole as internal standard is described. The separation was achieved on a reversed-phase column employing acetic acid-methanol as the mobile phase with spectrophotometric detection at 230 nm. Precise simultaneous quantitative analysis of the relative components has been achieved at levels of 0.1 microgram/ml for trimethoprim and 1.0 microgram/ml for both sulphamethoxazole and its N4-acetyl metabolite using 1 ml of serum of urine.

Chromatography, High Pressure Liquid↗
PubMed1981

Release of betamethasone 17-valerate from extemporaneous dilutions of a proprietary topical cream.

Six different vehicles for topical use were used to prepare 50% dilutions of Betnovate (betamethasone 17-valerate, 0.1%) cream. Blanching assessment as undertaken immediately after preparing the various dilutions and at 1 and 3 months thereafter. Few statistically significant differences were noted between any of the preparations tested indicating hat the rate of release of betamethasone 17-valerate is relatively unaffected by dilution. All preparations were assayed by a stability indicating high pressure liquid chromatographic technique for corticosteroid content. A diminution in the content of betamethasone 17-valerate in the E45 dilution was found 14 months after preparation. All other formulations tested were found to comply with label claim specifications.

Administration, Topical↗
PubMed1978

Comparative blanching activities of proprietary diflucortolone valerate topical preparations.

The blanching activities and hence bioavailabilities of the cream, ointment and fatty ointment preparations of Nerisone and Temetex (diflucortolone valerate 0.1%) were evaluated using an occluded and unoccluded blanching assay. These products were compared to Synalar ointment and cream (fluocinolone acetonide 0.025%), established topical corticosteroid preparations. Statistical analysis showed no significant differences between similar formulations of diflucortolone valerate. Significant differences were noted between diflucortolone valerate and fluocinolone acetonide preparations.

Administration, Topical↗