Quantitative determination of the ß-methyl carbapenem doripenem in powder for injection by a stability-indicating capillary zone electrophoresis method.

A capillary zone electrophoresis method for quantitative determination of doripenem in synthetic matrix was developed. The stability-indicating capability was performed applying stress testing protocols. The selected analytical conditions include 100 mM sodium borate buffer (pH 8.0) as run electrolyte, voltage of +15 kV, hydrodynamic injection of 5s (50 mBar), detection at 298 nm and temperature of analysis of 25 degrees C. The electrophoretic separation was carried out in a fused silica capillary (effective length 40 cm, 50 µm i.d.), using procainamide hydrochloride as internal standard. The proposed method showed quickness and reproducibility, with an analytical run in a total time of 5 min. The percentage of drug amount estimated was 101.33% (RSD = 0.80), with satisfactory intra-day and inter-day precision. In the recovery test, the method was found to be reliable and accurate in the drug quantitation (mean recovery = 101.86%). The robustness was performed applying the Plackett-Burman experimental design which confirmed the assay reliability. Based on results from forced degradation study, the stability-indicating capability was established, being observed a major degradation in alkaline, photolytic and thermal conditions. In comparison to HPLC method previously developed, the proposed capillary electrophoresis assay is statistically equivalent.

LC method for determination of prasugrel and mass spectrometry detection for thermal and alkaline degradation products.

A stability-indicating RP-LC method for the determination of prasugrel in tablets was developed and validated. Stress testing of prasugrel was carried out in accordance with ICH guidelines, where the drug was submitted to acidic and basic hydrolysis, oxidative, thermal and photolytic conditions. Prasugrel was unstable under all the conditions and the degradations products were analyzed by HPLC-UV. Furthermore, two main degradation products found under alkaline and thermal conditions were investigated by LC-MS. Based on the fragmentation patterns, two products resulted from hydrolysis of the acetate ester moiety of prasugrel were observed. Due the chemical equilibrium, tautomerism occurs between the ketone and alcohol functions justifying the similar molecular weight and fragment pattern obtained in degradation products analysis. Successful separation was achieved on a RP-18 octadecyl silane column using acetonitrile and triethylamine 0.5% mixture (50:50, v/v) as the mobile phase at 25 degrees C. The flow rate was 1.0 mL/min and the detector wavelength was 263 nm. The method proposed in this work was successfully applied to quality control of prasugrel and contribute to stability assessment of pharmaceutical products containing this drug.

Capillary zone electrophoresis for determination of vildagliptin (a DPP-4 inhibitor) in pharmaceutical formulation and comparative study with HPLC.

A stability-indicating capillary zone electrophoresis (CZE) method was validated for the determination of vildagliptin (VLG) in pharmaceutical dosage forms using ranitidine hydrochloride (RH) as internal standard. The CZE method was carried out in a fused silica capillary (64.5 cm total length and 56.0 cm effective length, 50 microm i.d.) by applying a potential of 25 kV (positive polarity), hydrodynamic injection by 50 mbar for 5 s and the temperature of the capillary cartridge was 25 degreesC. The selected background electrolyte (BGE) consisted of 25 mM potassium phosphate (pH 8.0) with UV/PDA detection at 207 nm. The electrophoretic separation was obtained within 6 min and was linear in the range of 50-200 microg/mL (r= 0.9994). The specificity and the stability-indicating capability were demonstrated through degradation studies, which also showed that there was no interference of the formulation excipients. The method was validated in accordance to ICH guidelines acceptance criteria for specificity, linearity, precision, accuracy, robustness and system suitability. The proposed method was compared with HPLC method previously validated for this drug, and statistical analysis showed no significant difference between the methods.

Development of a HPLC-UV method for the quantitative determination of four short-chain fatty acids and lactic acid produced by intestinal bacteria during in vitro fermentation.

A rapid and sensitive HPLC-UV method for the quantitative determination of four short-chain fatty acids (SCFAs) and lactic acid (LA) produced during in vitro fermentation is presented. Extraction of SCFAs from supernatants of bacterial cultures is aggravated due to their polarity and volatility. Detection can only be performed at a short, non-selective UV wavelength (210nm), due to the lack of any significant chromophore. Therefore special attention was paid to the optimization of the sample preparation procedure and the HPLC-UV conditions. The final extraction procedure consisted of a liquid-liquid back extraction using diethylether. Prior to HPLC-UV analysis the samples were acidified (pH<2) in order to improve retention of the SCFA's and LA on the Hypersil Gold aQ column. Matrix-matched calibration graphs were prepared for all analytes of interest (range 0.5-50mM) and correlation and goodness-of-fit coefficients were between 0.9951-0.9993 and 3.88-8.27%, respectively. Limits of detection and quantification ranged from 0.13 to 0.33mM and 0.5 to 1.0mM, respectively. The results for the within-day and between-day precision and accuracy fell within the ranges specified. The reported validated method has been successfully used for the in vitro screening of supernatants of bacterial cultures for the presence of butyric acid, aiming to select for butyric acid-producing bacteria. In addition, the method has been used to determine the production pattern of selected fatty acids by bacterial species isolated from human feces and chicken caeca.

Photodegradation kinetics, cytotoxicity assay and determination by stability-indicating HPLC method of mianserin hydrochloride.

A stability-indicating HPLC method for the determination of mianserin hydrochloride in coated tablets was developed and validated. Also, drug photodegradation kinetics and cytotoxicity were determined. Chromatographic analyses were performed in an Ace RP-18 octadecyl silane column (250 mm x 4.6 mm i.d., particle size 5 microm) maintained at ambient temperature (25 degrees C). The mobile phase was composed of methanol, 50 mM monobasic potassium phosphate buffer and 0.3% triethylamine solution adjusted to pH 7.0 with phosphoric acid 10% (85:15, v/v) in isocratic mode at a flow rate of 1.0 mL x min(-1). The performed degradation conditions were: acid and basic media with HCl 1.0 M and NaOH 1.0 M, respectively, oxidation with H2O2 3% and the exposure to UV-C light. No interference in the mianserin hydrochloride elution was verified by degradation products formed. Linearity was assessed and ANOVA showed non-significant linearity deviation (p > 0.05). Adequate results were obtained for repeatability, intermediate precision, accuracy and robustness. The photodegradation kinetics of mianserin hydrochloride was evaluated in methanol. The degradation of mianserin could be better described as zero order kinetic (r = 0.9982). The UV-C degraded samples of mianserin hydrochloride were also studied in order to determine the preliminary cytotoxicity in vitro against mononuclear cells.

Stability indicating method for sodium montelukast in pharmaceutical preparations by micellar electrokinetic capillary chromatography.

A simple, reliable micellar electrokinetic chromatography method (MEKC) for the determination of sodium montelukast in coated tablets was developed and validated. Successful results were obtained with 10 mmol L(-1) borate buffer and 30 mmol L-(1) sodium dodecyl sulfate at pH 9.4, injection time of 5.0 s, an applied voltage of 25 kV and a column temperature of 25 degrees C. The detector response for sodium montelukast was linear over the concentration range from 20 to 100 microg mL(-1) (r = 0.9995). The intra and inter-day precision showed suitable results (RSD < 1.46%). The analytical method accuracy was 99.67% (RSD = 1.11%). The limits of detection and quantitation were 0.75 and 2.00 microg mL(-1) respectively. The method demonstrated robustness and showed to be viable for the sodium montelukast determination in pharmaceutical dosage form.

LC: analysis of photodegradation kinetics of nitazoxanide in pharmaceutical formulations.

Nitazoxanide is a new broad-spectrum, antiparasitic drug agent. The photodegradation of nitazoxanide was studied in order to investigate the degradation kinetics of this drug. The analyses of the degraded samples were performed by a stability-indicating liquid chromatographic method. The degradation was carried out in acetonitrile with coated tablets or oral suspension powder in quartz cells under UVC light at 254 nm. The kinetics parameters, such as order of reaction, rate constants, half-life (t(1/2)), and the time when 90% of the drug original concentration was left, were determined. The photodegradation of nitazoxanide for both pharmaceutical formulations in acetonitrile solution shows a zero-order kinetics under the applied experimental conditions. The obtained results confirm the reliability of the chromatographic method for determining the kinetics run of nitazoxanide in the presence of its degradation products. The present study reveals the photolability of the drug in solution. Thus, appropriated photoprotection is recommended during the manipulation of the drug.

Determination of dexamethasone acetate in cream by HPLC.

The aim of this research was to validate a high performance liquid chromatographic method for the quantitative determination of dexamethasone acetate contained in cream preparation. A MetaSil octadecyl silane (250 x 4.6 mm, 5 microm) column, a methanol: water (65:35; v/v) mobile phase (1.0 ml min(-1)) and an UV detector (set at 254 nm) were used to evaluate the parameters: linearity, precision, accuracy, specificity, as well as, quantitation and detection limits. The calibration curve showed a correlation coefficient of 0.9999. The precision was demonstrated by the relative standard deviation (RSD) of 0.53. The recovery test resulted in an average of 97.85%, what confirmed the accuracy of the method. The quantitation and detection limits determined were 1.41 and 0.47 microg ml(-1), respectively. The specificity test showed there was no interference in the drug peak.

Microbiological assay for azithromycin in pharmaceutical formulations.

The validation of a microbiological assay, applying the cylinder-plate method, for the determination of the antibiotic azithromycin is described. Using a strain of Micrococcus luteus ATCC 9341 as the test organism, azithromycin at concentrations ranging from 0.1 to 0.4 microgml(-1) could be measured in capsules and suspensions. A prospective validation of the method showed that it was linear (r=0.998), precise (RSD=1.40-capsules; RSD=1.19-powder for suspension and RSD=1.73-oral suspension) and accurate (it measured the added quantities). We conclude that the microbiological assay is satisfactory for quantitation of in vitro antibacterial activity of azithromycin.

Essential oils from Piper cernuum and Piper regnellii: antimicrobial activities and analysis by GC/MS and 13C-NMR.

The essential oils of Piper cernuum and Piper regnellii leaves were analyzed by gas chromatography-mass spectrometry (GC-MS) and the results were compared to that obtained by means of a program designed to analyse (13)C-NMR data of complex mixtures. Bicyclogermacrene (21.88 %)/beta-caryophyllene (20.69 %) and myrcene (52.60 %)/linalool (15.89 %) were the major constituents in essential oil from leaves of P. cernuum and P. regnellii, respectively. Both essential oils presented growth inhibitory activities against Staphylococcus aureus and Candida albicans.

Method validation for diclofenac sodium in pharmaceuticals by capillary electrophoresis.

A capillary electrophoresis method for the determination of diclofenac sodium in a commercial and simulated tablet formation has been described. The aim of this research was to develop a rapid, simple, efficient, and economical method to determine diclofenac sodium in pharmaceutials. The analysis was carried out in a bare silica capillary (75 pm i.d.) with a total length of 50 cm (28 cm to the detector) with a buffer solution containing 20 mM sodium tetraborate, pH 9.23. The applied voltage was 20 kV. Detection was achieved by ultraviolet absorption at 276 nm. Acetaminophen was used as an internal standard. The calibration curve was linear to the concentration range from 40.0 to 120.0 microg/mL with a correlation coefficient of 0.9992. The percentage recovery was found to be 103.12 +/- 0.91. The results showed that the method allows the determination of diclofenac sodium in commercially available pharmaceutical preparations.

Acute phosphate intoxication in seven infants under parenteral nutrition.

After major surgery, seven infants aged 4 to 29 weeks, under parenteral nutrition, received monosodium phosphate (4.2 to 14.3 mEq/kg body weight) instead of prescribed calcium gluconate. The wrong solution was perfused during 16 hours. At the 15th hour, blood samples showed hyperphosphatemia in all (8.0 to 14.4 mg/100 mL) and hypocalcemia in four infants (6.1 to 8.0 mg/100 mL), but all were asymptomatic. Under a perfusion of glucose in water, calcemia and phosphatemia returned to normal within 24 hours. In a review of the pediatric literature, we found 11 subjects with symptomatic acute phosphate intoxication, who also presented with hypocalcemia and hyperphosphatemia. The differences were that they received high bolus doses of phosphate orally or rectally and showed symptomatic features. Normalization of the calcemia occurred only when hyperphosphatemia was corrected throughout intravenous hydration.

Particularities in children poisoning.

Poisoning in childhood mostly by ingestion of toxics, remains a frequent and potentially severe accident. They are generally avoidable and preventive programs should be reinforced. The action of the centre antipoison (CAP) in this field must be encouraged. Methods of emergency gastrointestinal decontamination are presented. It should facilitate the acute management of children suffering from poisoning by ingestion. Carbon monoxyde poisoning is very frequent and more severe than we usually think because it induces various sequellae. We developed a prospective study to determine the occurrence of unsuspected carbon monoxyde poisoning in children presenting a variety of symptoms.