Development and validation of HPLC-DAD method for the simultaneous determination of amoxicillin, metronidazole and rabeprazole sodium. Application to spiked simulated intestinal fluid samples.

This work deals with the development, validation and application of an HPLC-DAD method for the determination of a ternary mixture containing amoxicillin (AX), metronidazole (MZ) and the proton pump inhibitor rabeprazole sodium (RB). This triple therapy is used for treatment of Helicobacter pylori infection. Effective chromatographic separation between the three drugs was achieved using Thermo Hypersil BDS-C8 (4.6×250mm, 5µm particle size) column and a mobile phase composed of phosphate buffer pH 7 and acetonitrile (70: 30, by volume). The mobile phase was pumped isocratically at a flow rate of 1 mL/min. Quantification of the analytes was based on measuring their peak areas at 230nm for both AX and RB, and at 319nm for MZ. AX, MZ and RB eluted at retention times 2.36, 3.55 and 8.72min respectively. The reliability and analytical performance of the proposed HPLC procedure were statistically validated with respect to linearity, ranges, precision, accuracy, selectivity, robustness, detection and quantification limits. The linear dynamic ranges were 25-250, 25-250 and 5-50µg/mL for AX, MZ and RB respectively with correlation coefficients>0.9998. The validated method was successfully applied to the analysis of several laboratory-prepared mixtures as well as simulated intestinal fluid samples spiked with the three drugs.

[Prostate cancer]. / Cancer de la prostate.

Radiation therapy is now widely accepted as an efficacious treatment of localized prostate cancer. The technical developments of recent years have enabled the evolution of a three-dimensional conformal radiotherapy, offering a better adaptation of the dose distribution, and leading therefore to preserve organs at risk. In addition, the required dose delivered to the target volume permit physician to increase the total dose if necessary. This requires a thorough knowledge of the radio-anatomy of the prostate, the natural history of the disease but also the ballistics and dosimetry. The objectives of this work were to detail epidemiology and radio-anatomy of the prostate cancer. In addition, conformal radiation modalities are illustrated by a case report.

[Postoperative radiotherapy for prostate cancer]. / Radiothérapie postopératoire du cancer de la prostate.

More than one third of patients with localized prostate cancer at diagnosis who receive radical prostatectomy have histologically extraprostatic disease. Three randomized trials have demonstrated a significant benefit of postoperative radiotherapy for these patients in terms of biochemical progression-free survival, overall survival or metastasis-free survival in function of each study, at the cost of moderate acute and late toxicity. The technical developments of recent years have enabled the evolution of a three-dimensional conformal radiotherapy, with better adaptation of the dose distribution to the shape of target volumes to preserve organs at risk while delivering the required dose volume target. This requires a thorough knowledge of the prostate cancer radioanatomy, ballistics and dosimetry. Purpose of this work was to specify epidemiological and radioanatomy characteristics for this tumor type and conformal radiation modalities illustrated by a case report.

[Paranasal sinus carcinoma]. / Cancer des sinus de la face.

Cancers of the paranasal sinuses are rare tumors, with treatment based on a multidisciplinary approach. Surgery and radiation therapy, possibly associated with chemotherapy are used to obtain 5 years specific survival rate of 60-70 %. Advances in radiotherapy, including the use of imaging for 3D conformal approach require precise knowledge of the radioanatomy for this type of tumor to determine the different volumes of interest. Purpose of this study was to specify radioanatomy and conformal radiation modalities for cancers of the sinuses, and is illustrated by a case report.

[Conformal intensity modulated radiation therapy for localized prostate cancer: Toward a new standard]. / Radiothérapie de conformation avec modulation d'intensité dans le cancer de prostate : vers un nouveau standard.

Radiation therapy is now widely accepted as an efficacious treatment of localized prostate cancer. Recent advances, namely with the development of conformal radiotherapy, allowed to increase the total dose in the target volumes with greater local control. A forward step achieved with intensity modulated radiotherapy (IMRT) in terms of therapeutic ratio between target volumes and critical organs. IMRT offers an inverse planning dosimetry and a modulation of the fields during irradiation. This article presents recent technical and clinical advances in IMRT focused on prostate cancer.

[Pilot study of conformal intensity modulated radiation therapy for localized prostate cancer].

PURPOSE: - To report our experience on treatment planning and acute toxicity in 16 patients suffering from clinically localized prostate cancer treated with high-dose intensity-modulated radiation therapy (IMRT). PATIENTS AND METHODS: - Between March 2001 and October 2002, 16 patients with clinically localized prostate cancer were treated with IMRT. Treatment planning included an inverse-planning approach, and the desired beam intensity profiles were delivered by dynamic multileaf collimation. All patients received the entire treatment course with IMRT to a prescribed dose of 78 Gy. All IMRT treatment plans were compared with a theoretical conventional three-dimensional conformal radiation therapy (3D-CRT). Acute lower gastro-intestinal (GI) and genito-urinary (GU) toxicity was evaluated in all patients and graded according to the Common Toxicity Criteria for Adverse Events version 3.0 (CTCAE v. 3.0). A relationship between dose volume and clinical toxicity was evaluated. RESULTS: - Ninety-five percent of the PTV2 received more than 76 Gy using IMRT or 3D-CRT with no difference between both methods. The dose-volume histogram mean obtained for the PTV2 was not different between IMRT and 3D-CRT. IMRT improved homogeneity of the delivered dose to the PTV2 as compared with 3D-CRT (7.5 vs 9%, respectively). Ninety-five percent of the PTV1 received 5 Gy more using IMRT with protection of the bladder and the rectum walls. The benefit was considered below 75 and 70 Gy for the wall of the bladder and the rectum, respectively. Grade 2 GI and GU toxicity was observed in four (25%) and five (31%) patients, respectively. No grade 3 toxicity was observed. There was a trend towards a relationship between the mean rectal dose and acute rectal toxicity but without statistical significant difference (P =0.09). CONCLUSION: - Dose escalation with IMRT is feasible with no grade 3 or higher acute GI or GU toxicity. Examination of a larger cohort and longer-term follow-up are warranted in the future.

Sensitive spectrofluorimetric and spectrophotometric methods for the determination of thonzylamine hydrochloride in pharmaceutical preparations based on coupling with dimethylbarbituric acid in presence of dicyclohexylcarbodiimide.

Two sensitive and selective spectrophotometric and spectrofluoimetric procedures were developed for the determination of thonzylamine hydrochloride (THAH) in tablets and nasal drops. The methods are based on König reaction which resulted in an orange-yellow fluorescent product. The orange-yellow product of the interaction between the dicyclohexylcarbodiimide (DCC), THAH and dimethylbarbituric acid (DMBA) showed an absorption maximum at 492 nm, a first-derivative signal at 494 nm and a fluorescence emission peak at 518 nm (lambda(ex)=492 nm). The orange-yellow color was found to be stable for at least 2 h. The reaction conditions were studied and optimized. The reaction obeys Beer's law over the ranges 8-20 and 0.2-2.0 microg ml(-1) for the derivative spectrophotometric and fluorimetric measurements, respectively. The detection limits were found to be 0.29 and 0.018 microg ml(-1) for the spectrophotometric and fluorimetric measurements, respectively. The proposed methods were applied to the analysis of pharmaceutical formulations containing THAH, either alone or in combination with naphazoline nitrate.

Simultaneous determination of melatonin-pyridoxine combination in tablets by zero-crossing derivative spectrophotometry and spectrofluorimetry.

Two methods have been developed for the analysis of melatonin (M) and pyridoxine hydrochloride (PH) in combination. The first method depends on first- and second-derivative ultraviolet spectrophotometry, with the zero crossing technique of measurement. First-derivative amplitudes at 296 nm and second-derivative amplitudes at 294 and 322 nm are selected for the determination of M and PH, respectively. The second method is based on the native fluorescence of both M and PH, in methanol and 0.1 M hydrochloric acid, respectively, after a preliminary solvent extraction procedure. The relative standard deviation of both methods was less than 2.0%. The two methods have been successfully applied to the determination of both drugs in laboratory-prepared mixtures and in tablets.

Spectrofluorimetric determination of guanethidine sulphate, guanoxan sulphate and amiloride hydrochloride in tablets and in biological fluids using 9,10-phenanthraquinone.

A highly sensitive spectrofluorimetric method for the determination of some drugs of the monosubstituted guanidine derivatives in laboratory made tablets, in spiked human serum and in urine samples is presented. The method is based on the reaction of guanethidine sulphate (I), guanoxan sulphate (II) and amiloride hydrochloride (III) with 9,10-phenanthraquinone (IV) to give highly fluorescent derivatives. The linearity ranges were found to be 0.06-0.96 mug/ml for (I) and (II) and 0.04-0.28 mug/ml for (III), with relative standard deviation less than 2%. Mean percentage recoveries for tablets were found to be 99.9 +/- 1.3, 100.5 +/- 1.1 and 100.0 +/- 1.6 for I, II and III, respectively. For I and III the results are highly correlated with the B.P. methods. Using the synchronous fluorimetry, differentiation between I and II was possible. Chloroform, dichloromethane and ethyl acetate have been used to extract I, II and III, respectively from serum and urine at basic pH, followed by applying the proposed fluorimetric method. Percentage recoveries were found to be 95.7-102.2%. The limit of detection is 0.04 mug/ml for I and II and 0.02 mug/ml for III.

Simultaneous determination of theophylline and guaiphenesin by third-derivative ultraviolet spectrophotometry and high-performance liquid chromatography.

Two methods are described for the simultaneous determination of theophylline and guaiphenesin in combined pharmaceutical dosage forms. The first method depends on third-derivative ultraviolet spectrophotometry, with the zero crossing technique of measurement. Third-derivative amplitudes at 222 and 278 nm were selected for the assay of guaiphenesin and theophylline, respectively. The second method is based on high-performance liquid chromatography on a reversed-phase column using a mobile phase of 0.01 mol dm-3 sodium dihydrogen phosphate-methanol-acetonitrile (8 + 2 + 1) (pH 5.5) with detection at 245 nm. Both methods showed good linearity, precision and reproducibility. The proposed methods were successfully applied to the determination of these drugs in laboratory-prepared mixtures and in capsules or elixir.

High-performance liquid chromatographic determination of floctafenine and its major metabolite, floctafenic acid in plasma.

A simple, rapid and selective high-performance liquid chromatographic method for the determination of floctafenine and its major metabolite, floctafenic acid, in plasma is reported. Plasma samples were purified using the mobile phase as a protein precipitant. The supernatant containing parent compounds and diazepam (internal standard) were eluted from a 5 micron C 18 reversed-phase column at ambient temperature. The mobile phase consisted of 0.05 M sodium acetate:acetonitrile: methanol (200:100:100 v/v/v) adjusted to pH 5 and pumped isocratically at a flow rate of 1.5 ml/min. The effluent was monitored at 350 nm. Quantification was achieved by the measurement of the peak-height ratio of each drug to the internal standard. The mean percentage recoveries from plasma samples spiked with floctafenine and floctafenic acid ranged from 88.13 to 101.93%. Detection limits were 100 ng/ml for floctafenine and 50 ng/ml for floctafenic acid. The coefficients of variation (RSD, %) for within-day and day-to-day analysis were less than 8%.

Determination of isothipendyl or dimethothiazine with their sulphoxides using third- and fourth-derivatives spectroscopy on a diode-array spectrophotometer.

Third- and fourth-derivative spectrophotometry (3D + 4D), with a diode-array spectrophotometer, has been used for the assay of mixtures of each of isothipendyl hydrochloride (I) and its sulphoxide (II) or dimethothiazine mesylate (III) and its sulphoxide (IV). The parent compounds have been determined by measuring the 3D at 256 nm, 246-256 nm and 256-264 nm and 4D at 250 nm for (I) and 3D at 255 nm or 283 nm and 4D at 257 nm for (III). The sulphoxides have been assayed by measuring the 3D at 285-290 nm and 4D 285-290 nm for (II) and 3D at 305 nm and 4D at 303-310 nm for (IV). Beer's law is obeyed and the detection limits for the proposed 3D and 4D has been calculated. The recovery of these drugs and their sulphoxides in laboratory-made mixture and dosage forms has been reported.

Colorimetric determination of some penicillins and cephalosporins with 2-nitrophenylhydrazine hydrochloride.

A simple and sensitive calorimetric method for the determination of some penicillins and cephalosporins is presented. The method is based on reaction with 2-nitrophenylhydrazine hydrochloride in presence of dicyclohexylcarbodi-imide and pyridine. The violet colour of the resulting acid hydrazide is measured at the appropriate wavelength. The method has been applied to determination of these antibiotics in bulk and dosage forms, with a coefficient of variation less than 2%.

Application of transformation algorithm and nonparametric calculation in determining the reference intervals of some urine constituents and characteristics.

We have applied a multi-stage computer algorithm for normalization of distributions and calculation of reference intervals of some urine characteristics and constituents. The study analyzed 24-h urines, collected from adult male Saudis from different socioeconomic classes, for volume, pH, osmolality, specific gravity, creatine, creatinine, urea and uric acid. Frequency distributions, for each analyte, were found to be nongaussian as judged by the coefficients of skewness and kurtosis, chi 2 and Kolmogorov-Smirnov tests, and from probability plots. Data were transformed to gaussian distributions by multistage log-power transformation. Stepwise, this procedure removed skewness and residual kurtosis. Using the gaussian transformed data the reference intervals were estimated parametrically as the mean +/- 2 SD. In addition, the non-parametric percentile technique was applied to estimate these values. The former intervals were found to have narrower 0.90 confidence limits than the latter. When established limits were compared with those reported for Western subjects urine volume and uric acid showed the most marked variation.

Spectrophotometric determination of some 1,4-benzodiazepines by use of orthogonal polynomials.

A direct spectrophotometric method for the determination of some 1,4-benzodiazepines, namely, nitrazepam, prazepam and dipotassium chlorazepate, in the presence of their degradation products, is presented. The method depends upon the use of orthogonal polynomials, to eliminate interferences by degradation products to the absorption spectra of the intact drugs. The method was proved using synthetic mixtures of the intact drugs with their respective degradation products and its suitability to monitor for the stability of the drugs was demonstrated. The method has been applied to the determination of these drugs in dosage forms, with a coefficient of variation less than 2%.