Biomedical subjects

I Panderi

Publications and source records attributed to I Panderi.

10 recordsLinked to original sources

PubMed2004

Development and validation of a high-performance liquid chromatographic method for the determination of buspirone in pharmaceutical preparations.

A stability indicating, reversed-phase high-performance liquid chromatographic method was developed and validated for the determination of buspirone (Bsp) in pharmaceutical dosage forms. The use of a semi-micro XTerra MS C18 (150 mm x 3.0 mm i.d., 5 microm particle size) analytical column, results in substantial reduction in solvent consumption and increased sensitivity. The mobile phase consisted of a mixture of 0.010 M ammonium acetate (pH 4.0) and methanol (55:45, v/v), pumped at a flow rate 0.30 ml min-1. The UV detector was operated at 245 nm. The retention times for lidocaine (Ldc), which was used as internal standard, and buspirone were 4.57 and 7.72 min, respectively. The calibration graph was ranged from 1.00 to 5.00 microg ml-1, while detection and quantitation limits were found to be 0.22 and 0.67 microg ml-1, respectively. The intra- and inter-day relative standard deviation (% R.S.D.) values were less than 1.94%, while the relative percentage error (% Er) was less than 4.0% (n = 5). The method was applied to the quality control of commercial tablets and content uniformity test and proved to be suitable for rapid and reliable quality control.

Anti-Anxiety Agents↗

PubMed2002

A validated LC method for the determination of clopidogrel in pharmaceutical preparations.

A stability indicating, reversed-phase high-performance liquid chromatographic method was developed and validated for the determination of clopidogrel in pharmaceutical dosage forms. The determination was performed on a semi-micro column, BDS C8 (250 x 2.1 mm i.d., 5 microm particle size); the mobile phase consisted of a mixture of 0.010 M sodium dihydrogen phosphate (pH 3.0) and acetonitrile (35:65, v/v), pumped at a flow rate 0.30 ml min(-1). The UV detector was operated at 235 nm. The retention times for clopidogrel and naproxen, which was used as internal standard, were 3.08 and 6.28 min, respectively. Calibration graphs are linear (r better than 0.9991, n=6), in concentration range 1.00-3.00 microg ml(-1) for clopidogrel. The intra- and inter-day RSD values were less than 1.96%, while the relative percentage error E(r) was less than 2.0% (n=5). Detection and quantitation limits were 0.12 and 0.39 micro ml(-1), respectively. The method was applied in the quality control of commercial tablets and content uniformity test and proved to be suitable for rapid and reliable quality control.

Calibration↗

PubMed2002

Kinetics of the acidic and enzymatic hydrolysis of benazepril HCl studied by LC.

A reversed-phase high-performance liquid chromatographic (HPLC) method was developed and validated for the kinetic investigation of the chemical and enzymatic hydrolysis of benazepril hydrochloride. Kinetic studies on the acidic hydrolysis of benazepril hydrochloride were carried out in 0.1 M hydrochloric acid solution at 50, 53, 58 and 63 degrees C. Benazepril hydrochloride appeared stable in a pH 7.4 phosphate buffered solution at 37 degrees C and showed susceptibility to undergoing in vitro enzymatic hydrolysis with porcine liver esterase (PLE) in a pH 7.4 buffered solution at 37 degrees C. Benazeprilat appeared to be the major degradation product in both (chemical and enzymatic) studies of hydrolysis. Statistical evaluation of the proposed HPLC methods revealed their good linearity and reproducibility. Relative standard deviation (R.S.D.) was less than 4.76, while detection limits for benazepril hydrochloride and benazeprilat were 13.0 x 10(-7) and 9.0 x 10(-7) M, respectively. Treatment of the kinetic data of the acidic hydrolysis was carried out by non-linear regression analysis and k values were determined. The kinetic parameters of the enzymatic hydrolysis were determined by non-linear regression analysis of the data using the equation of Michaelis-Menten.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1998

Acidic hydrolysis of bromazepam studied by high performance liquid chromatography. Isolation and identification of its degradation products.

A kinetic study on the acidic hydrolysis of bromazepam was carried out in 0.01 M hydrochloric acid solution at 25 and 95 degrees C. A reversed-phase HPLC method was developed and validated for the determination of bromazepam and its degradation products. Bromazepam degraded by a consecutive reaction with a reversible first step. Two degradation products were isolated and identified by infrared, 1H and 13C nuclear magnetic resonance and mass spectroscopy. Spectroscopic data indicated that N-(4-bromo-2-(2-pyridylcarbonyl)phenyl)-2-aminoacetamide was the intermediate degradation product of this acid hydrolysis, whereas 2-amino-5-bromophenyl-2-pyridylmethanone was the final one. Therefore, the mechanism of this acid-catalysed hydrolysis involved initial cleavage of the 4,5-azomethine bond, followed by slow breakage of the 1,2-amide bond. Statistical evaluation of the HPLC method revealed its good linearity and reproducibility. Detection limits were 3.8 x 10(-7) M for bromazepam, 6.25 x 10(-7) M for the intermediate and 8.16 x 10(-7) M for the benzophenone derivative.

Acetamides↗

PubMed1998

Determination of piroxicam and its major metabolite 5-hydroxypiroxicam in human plasma by zero-crossing first-derivative spectrophotometry.

A zero-crossing first-derivative spectrophotometric method for the determination of piroxicam and its major metabolite 5-hydroxypiroxicam (5-HP) in human plasma is described. This technique permits the quantification of compounds with closely overlapping spectral bands without any separation step. The method consists of direct extraction of the less-ionised forms of piroxicam and 5-hydroxypiroxicam with pure diethyl ether. First derivative values at 343.5 and 332.5 nm for piroxicam and 5-HP, respectively, were obtained. The absolute recovery of the method was found to be 89.4% for piroxicam and 90.3% for 5-HP. Calibration graphs are linear (r better than 0.9998), with zero-intercept, in the concentration range 0.5-12.0 micrograms ml-1 for both compounds. The limits of quantification attained according to the IUPAC definition were 0.29 and 0.27 micrograms ml-1 for piroxicam and 5-HP, respectively. The results obtained by the proposed method were in good agreement with those found by the high-performance liquid chromatographic method (HPLC).

Chromatography, High Pressure Liquid↗

PubMed1997

Prediction of distribution coefficient from structure. 1. Estimation method.

A method has been developed for the estimation of the distribution coefficient (D), which considers the microspecies of a compound. D is calculated from the microscopic dissociation constants (microconstants), the partition coefficients of the microspecies, and the counterion concentration. A general equation for the calculation of D at a given pH is presented. The microconstants are calculated from the structure using Hammett and Taft equations. The partition coefficients of the ionic microspecies are predicted by empirical equations using the dissociation constants and the partition coefficient of the uncharged species, which are estimated from the structure by a Linear Free Energy Relationship method. The algorithm is implemented in a program module called PrologD.

Algorithms↗

PubMed1997

Prediction of distribution coefficient from structure. 2. Validation of Prolog D, an expert system.

Prolog D is a program that formalizes, in a controllable and reproducible manner, an algorithm developed to predict distribution coefficients of ionizable compounds at a given pH and varying counterion concentrations. Its predictive power has been evaluated with experimental log D values measured under standard conditions of buffers and ionic strength. Calculations were performed with the three different options for the estimation of partition coefficients (log P) implemented in the program. Considering the diversity of test compounds as well as the present state of the art in log P and pKa predictions, Prolog D proved to be very efficient and can be used as a tool to provide lipophilicity data. Prediction patterns and correlations with the observed data are of almost equal quality for all options, permitting acceptable results for 80% of the data.

Chemistry, Physical↗

PubMed1994

Simultaneous determination of clopamide-pindolol combination in tablets by zero-crossing derivative spectrophotometry.

A first-derivative spectrophotometric method, using a 'zero-crossing' technique of measurement has been used for determining clopamide-pindolol mixture in tablets. In the first-derivative mode the zero-crossing points of clopamide and pindolol occur at 272.6 and 262.4 nm, respectively. The relative ease offered by this technique for the quantification of these drugs with closely overlapping bands was demonstrated. The linearity of the calibration curves was satisfactory (r = 0.9998) and the precision (RSD%) better than 1.89. Detection limits were 0.50 and 0.44 micrograms ml-1 for pindolol and clopamide, respectively. No spectral interferences from tablet excipients were found. Applications are given for the assay of commercial tablets and content uniformity test. The procedures proved to be suitable for rapid and reliable quality control.

Clopamide↗

PubMed1994

Second-derivative spectrophotometric determination of naproxen in the presence of its metabolite in human plasma.

A second-derivative spectrophotometric method for the determination of naproxen in the absence or presence of its 6-desmethyl metabolite in human plasma is described. The method consists of direct extraction of the non-ionized form of the drug with pure diethyl ether and determination of the naproxen by measuring the peak amplitude (mm) in the second-order derivative spectrum at a wavelength of 328.2 nm. The efficiency of the extraction procedure expressed by the absolute recovery was 94.6 +/- 0.7% (mean +/- s) for the concentration range tested, and the limit of quantification attained according to the IUPAC definition was 2.42 mg l-1. The linear dynamic range for naproxen was 5.0-100.0 mg l-1, the correlation coefficient for the calibration graphs was excellent, r = 0.99993 (n = 6), the precision (Sr) was better than 4.58% and the accuracy was satisfactory (Er < 2.32%). The results obtained by the proposed method were in good agreement with those found by an HPLC method.

Biotransformation↗

PubMedDate not supplied

Prediction of distribution coefficients from structure. Comparison of calculated and experimental data for various drugs.

The efficiency of the program PrologD to predict distribution coefficients (D) at any pH and pairing ion concentration has been tested using experimental logD values for various drugs measured under standard conditions of buffers and ionic strength. Clonidine derivatives, fluoroquinolones and beta-blockers were included as particular pharmacological classes within the testing data set. Calculations were performed using the three logP estimation options implemented in the program. PrologD proved to be very efficient and can be of great advantage in drug research. Prediction patterns and correlations between experimental and calculated data indicate acceptable results for more than 80% of the data. In addition, comparable studies using the different options permitted suggestions for the more suitable logP estimation method in respect of the particular classes of compounds.

Animals↗