Spectroscopic study of the experimental parameters controlling the structural properties of chitosan-Ag nanoparticles composite.

Chitosan as reducing, stabilizing and capping agent was used to synthesize chitosan-silver nanoparticles composite under different experimental conditions of temperature or time. The UV-Vis spectra exhibited a single peak at 430nm which provided strong evidence for the formation of surface plasmon resonance (SPR) band of Ag nanoparticles. The rate of the increase of this absorbance with temperature increases with increasing the time of reduction. It was found that the variation of the temperature from 60°C to 100°C and the time of reduction from 6h to 16h resulted in no significant changes in the intensities and positions of the FTIR absorption bands of the composite. The TEM micrographs showed distinct typical spherical silver nanoparticles separated from each other quite well at reduction temperature range (60-80°C) and displayed some of accumulations at high temperature range (90-100°C). The TEM micrographs investigation indicated various shapes with different reduction time. The SEM images of the prepared samples were discussed.

Investigation of glass-ionomer cements using differential scanning calorimetry.

Six commercial glass-ionomer cements commonly used for various dental applications have been investigated using differential scanning calorimetry (DSC). The heat-flow behaviour and heat capacity of the cements were measured during isothermal (at 37 degrees C) setting reactions. The DSC results show that all materials undergo an exothermic setting process, but with different enthalpies of reactions and different heat capacities; there are no remaining endo- or exothermic reactions after the setting of the cement. All materials examined were found to be effective thermal insulators.

Enantioselective disposition of hydroxychloroquine after a single oral dose of the racemate to healthy subjects.

1. Stereoselectivity in the disposition of hydroxychloroquine was investigated in 23 healthy males following a single oral dose of 200 mg racemic HCQ (rac-HCQ) sulphate. Total concentrations (R+S) and R/S ratios of HCQ and its metabolites were measured by stereoselective h.p.l.c. 2. HCQ was detected in whole blood and urine, up to 91 and 85 days after dosing, respectively. Metabolites could not be detected in whole blood while in urine detectable concentrations were still present after 85 days. The blood concentrations of HCQ enantiomers were measurable until 168 h post-dose. 3. R(-)-HCQ accounted for 62 +/- 3% (mean +/- s.d.) of the AUC of rac-HCQ AUC. The elimination half-life of S(+)-HCQ (457 +/- 122 h) was significantly shorter than that of R(-)-HCQ (526 +/- 140 h), partly due to its faster urinary excretion and hepatic metabolism. Its renal clearance was twice that of R(-)-HCQ (4.61 +/- 4.01 vs 1.79 +/- 1.30 1 h-1), and metabolites derived from the S-isomer represented 80-90% of the urinary recovery of the dose. 4. Over 85 days, 4.4 +/- 2.9 and 3.3 +/- 1.8% of the dose was recovered in urine as unchanged S(+)-HCQ and R(-)-HCQ, respectively. For the first 2 weeks, S(+)-HCQ excretion rate clearly surpassed that of R(-)-HCQ whereas afterwards the inverse was observed. However, since the first 2 weeks account for 95% of rac-HCQ renal excretion, the total urinary excretion of S(+)-HCQ clearly surpassed that of R(-)-HCQ.(ABSTRACT TRUNCATED AT 250 WORDS)

Stereoselective disposition of hydroxychloroquine and its metabolite in rats.

Racemic hydroxychloroquine-sulfate (HCQ-sulfate) was administered to rats orally. Groups of 9 male and 9 female rats received doses of 0, 8, 16, or 24 mg/kg/day for 6 weeks, followed by a reduction of the higher doses to 8 mg/kg/day for the duration of the study. Whole blood samples were collected at 0, 3, 6, 8, and 10 weeks, and eleven tissues were harvested after the tenth week. The concentrations and enantiomer ratios of the parent drug and three metabolites, desethylhydroxychloroquine (DHCQ), desethylchloroquine (DCQ), and bisdesethylchloroquine (BDCQ), were determined. The highest concentration of HCQ was found in the intestinal smooth muscle, and the lowest in the brain and adipose tissue. The highest concentrations of the metabolites were found in the liver, adrenals, and lung tissue. The metabolism of HCQ in the rats was found to be stereoselective with R/S > 1 for the drug and < 1 for the metabolites. Gender-specific differences in the proportions of the drug and its metabolites and their enantiomers in blood and tissue were found. Varying dosages appeared to have only a temporary influence on blood concentrations and not to effect the enantiomer ratios in blood. Only a limited number of tissues exhibited significant differences between dose groups. There were no observed differences in enantiomer ratios among the blood collection times.

A preliminary pharmacokinetic study of the enantiomers of the terfenadine acid metabolite in humans.

A stereoselective and sensitive achiral/chiral method for the determination of terfenadine acid metabolite in human plasma was developed. The metabolite was separated and quantitated using an achiral chromatographic procedure with a cyano column. The mobile phase was 1 mM sodium acetate buffer (pH 4.0) and acetonitrile (25:75% v/v) at a flow rate of 2 ml/min, at ambient temperature. The stereospecific resolution was accomplished using a chiral-AGP column and a mobile phase consisting of sodium acetate (0.01 M): methanol (98.7:1.3% v/v), and 20 mM di-n-butylamine at a flow rate of 1.2 ml/min. The column temperature was maintained at 32 degrees C. The eluent was monitored at 230 nm (excitation) and 300 nm (emission) with a cut-off filter at 270 nm. This assay was used for a pharmacokinetic study in five subjects after administration of a single dose of 60 mg of terfenadine. The t1/2 values of the two enantiomers were similar, but the AUC values of the (+)-enantiomer were 2.05-2.35 times higher than those of (-)-enantiomer.

Steady-state pharmacokinetics of hydroxychloroquine in rheumatoid arthritis patients.

Steady-state pharmacokinetics of hydroxychloroquine (HC) sulfate (Plaquenil) were studied in five volunteers with rheumatoid arthritis who had taken 6 mg/kg/d of the drug for at least six months. Blood samples were drawn at 0, 1, 2, 4, 6, 8, 12, and 24 hours following an oral dose. Both whole blood and plasma were assayed by an HPLC method for HC and its metabolites desethylhydroxychloroquine, desethylchloroquine, and didesethylchloroquine. A 24-hour urine collection was obtained and assayed for the same compounds. The pharmacokinetics of HC and its metabolites conformed to the model predicted by single-dose studies. During the 24-hour period the absorption phase and both early and late distribution phases were seen. Variation in mean maximum/minimum concentration was 40 percent. Renal clearance accounted for only 16 percent of unchanged HC (22 percent of total drug and metabolites) and did not correlate with creatinine clearance.

Isocratic liquid chromatographic method for the determination of amoxapine and its metabolites.

An isocratic reverse-phase liquid chromatographic method for the determination of amoxapine and its major metabolites in human plasma utilizing UV detection is described. Plasma samples were extracted with ethyl acetate after pH adjustment. The reconstituted extracts were injected onto a cyanopropylsilane column and eluted with a mobile phase consisting of 65% acetonitrile and 35% sodium acetate buffer, 0.03 M and pH 6. The minimum detectable limit was less than 10 ng/mL of plasma. Possible interferences from other drugs which might be administered concurrently were studied. The reproducibility and precision of the method are demonstrated by the analysis of samples containing 25-600 ng/mL of plasma. The method is being applied successfully in our laboratory for the analysis of plasma from patients receiving amoxapine.

Effects of alcoholism on acetaminophen pharmacokinetics in man.

As a nonspecific measure of increased metabolic clearance, the kinetics of acetaminophen was studied in a group of nondrinking controls and alcoholics who had ceased drinking within the previous 48 hours. After a single 1-Gm dose of acetaminophen, blood levels showed a significant increase in nondrinking controls over the alcoholics. The area under the curve for the alcoholics was smaller than that for the controls. Further studies are indicated to determine the quantities of the various metabolites of acetaminophen in both groups.

Isocratic high-performance liquid chromatographic method for the determination of tricyclic antidepressants and metabolites in plasma.

An isocratic high-performance liquid chromatographic method for the determination of six tricyclic antidepressants and their major metabolites is presented. Hexane containing 0.5% diethylamine was used as an extraction solvent to minimize adsorption onto glass. A reversed-phase cyanopropylsilane column was used with a mobile phase consisting of 70% acetonitrile and 30% 0.03 M acetate buffer, pH 7.0. Good identification and quantitation were obtained by the use of both UV detection at 245 nm and spectrofluorometric detection with an excitation wavelength of 276 nm and an emission filter with a 370-nm cutoff. A minimum detectable limit of less than 5 ng/ml of plasma is possible with this system. The reproducibility and precision of the method are shown from the analysis of samples containing 20-400 ng/ml in plasma.

An isocratic high-pressure liquid chromatographic determination of naproxen and desmethylnaproxen in human plasma.

An isocratic high-pressure liquid chromatographic method for the determination of naproxen and its desmethyl metabolite in human plasma is presented. A reversed-phase octadecylsilane column was utilized with a mobile phase consisting of 55% methanol and 45% 0.10 M acetate buffer, pH 5.0. A spectrofluorometric detector with an excitation wavelength of 253 nm and a band pass filter provided high sensitivity with no interference from normal plasma constituents. The reproducibility and precision of the method were shown by analysis of spiked samples containing 2.5-70 micrograms/ml of plasma.

High-pressure liquid chromatographic determination of ibuprofen in plasma.

A high-pressure liquid chromatographic method is presented for the determination of ibuprofen in human plasma. Ibuprofen is extracted from plasma acidified with 1.0 M phosphoric acid using hexane containing p-phenylphenol as an internal standard. A reversed-phase octadecylsilane column was used with a liquid phase of 65% methanol and 35% 0.10 M acetate buffer (pH 5.0). A spectrofluorometric detector with an excitation wavelength of 253 nm and a band pass filter (230--420 nm) provided a detectable peak for 1 microgram of ibuprofen/ml of plasma. The effect of the pH and molarity of the mobile phase on the capacity factor was studied.

Sensitive high-pressure liquid chromatographic determination of disopyramide and mono-N-dealkyldisopyramide.

A high-pressure liquid chromatographic procedure for the accurate determination of disopyramide and its chief metabolite in plasma is presented. The method is suitable for monitoring patients receiving disopyramide therapy. A reversed-phase cyanopropylsilane column is utilized with a mobile phase of 50% acetonitrile and 50% 0.01 M sodium acetate buffer at pH 4.0. Absorption was monitored at 254 nm with a detection limit of 0.2 microgram/ml of plasma. The reproducibility and precision of the procedure were demonstrated on samples containing 0.50-12 microgram/ml of plasma.

Isolation and identification of a cannabinoid-like compound from Amorpha species.

The petroleum ether extracts from several plants have been screened on the plates with the chromogenic reagent Fast Blue B. salt. Extracts from different plant parts of Amorpha fruticosa, A. nanna, and A. canescens gave several spots with color and Rf values similar to those of Cannabis sativa extract. The major compound, amorphastilbol (1), was isolated by column chromatography, purified, and characterized by mp, elemental analysis, uv, ir, mass, prm, and cmr spectroscopy. Further information was obtained by analyzing the oxidation products of the compound. The evidence indicates that amorphastilbol is a phenolic stilbene terpenoid with a molecular formula of C24 H28 O2 and structural formula: (E,E)-2-(3',7'-dimethyl-2'-6'-octadienyl)-5-(2-phenylethenyl)-1,3-benzenediol. This is the first report of the isolation of a naturally-occurring stilbene derivative possessing a terpenoid moiety.

Sensitive high-pressure liquid chromatographic determination of propranolol in plasma.

A high-pressure liquid chromatographic method is presented for the determination of propranolol in human plasma. A reversed-phase cyanopropylsilane column was utilized with a liquid phase consisting of 70% acetonitrile and 30% 0.02 M acetate buffer, pH 7.0. A spectrofluorometric detector with an excitation wavelength of 276 nm and an emission filter with a 340-nm cutoff provided a detectable peak for 0.8 ng of propranolol/injection with this system. The reproducibility and precision of the method are shown from the analyses of samples containing 10--150 ng/ml of plasma.

High-speed liquid chromatographic determination of pilocarpine in pharmaceutical dosage forms.

A specific method for the direct determination of pilocarpine in aqueous pharmaceuticals in the presence of decomposition products, methylcellulose, and other ingredients usually present in pharmaceuticals is described. The method involves separation by high-speed liquid chromatography using, in series, octadecylsilane bonded to silica and cyanopropylsilane bonded to silica columns and a tetrahydrofuran-pH 9.2 borate buffer (3:7) eluant. Quantitation is achieved by monitoring the absorbance of the effluent at 254 nm and using a pyridine internal standard and a calibration curve prepared from known concentrations of pilocarpine nitrate. The reproducibility of the retention time and peak area was better than 2.0%.