Characteristics, Properties and Analytical Methods for Determination of Dropropizine and Levodropropizine: A Review.

Dropropizine is a peripheral antitussive drug that acts by inhibiting cough reflex through its action on the peripheral receptors and their afferent conductors. It is marketed in a racemic form or its pure enantiomer called levodropropizine and both are available worldwide in various drug dosage formulations such as tablets, sirup and oral solution. Due to the widespread use of antitussives in the clinic it is necessary to develop efficient analytical methodologies for quality control and also for pharmacokinetic, bioavailability and bioequivalence studies. This review presents a survey of the characteristics, properties and analytical methods used for drug determination, being carried out through scientific articles as well as in official compendia. From the analyzed studies, the majority reports the use of HPLC/UV techniques for drug determination, but also spectrophotometric UV/Vis methods as well as gas chromatography, and voltammetric, potentiometric and conductometric titration methods. In addition, the methodologies addressed the determination of dropropizine or levodropropizine in different types of matrices such as raw material, pharmaceutical formulations, plasma and urine. Despite the extensive clinical use of dropropizine, data from this review evidenced a still limited number of studies dealing with analytical methods for its determination in different matrices, which may be of concern since the applicability of these methods is important for quality assurance, efficacy and safety of the medicine.

Chemometric-Assisted Spectrophotometric Method for the Simultaneous Quantitative Determination of Ezetimibe and Simvastatin in Their Combined Dosage Forms.

The multivariate method, partial least-squares (PLS), was used as a calibration procedure for the simultaneous UV spectrophotometric determination of ezetimibe and simvastatin in their pharmaceutical forms. The method was developed and satisfactorily validated according to International Conference on Harmonization guidelines with respect to specificity, linearity, precision, accuracy, and robustness. In this study, the PLS algorithms are based on the absorption spectra of 25 different mixtures of drugs obtained by a multilevel factorial design. The method was linear in the concentration range of 2-8 µg/mL for ezetimibe and 4-16 µg/mL for simvastatin (r2 > 0.99; n = 7) at wavelengths of 238 and 247 nm, respectively. The LOD and LOQ were 0.28 and 0.93 µg/mL for ezetimibe and 0.16 and 0.53 µg/mL for simvastatin, respectively. Precision and accuracy data, evaluated by RSD, were lower than 2%. The method, which proved to be robust, was performed with a 2n full-factorial design. The validated method is simple and low cost, has a low use of polluting reagents, and is environmental friendly. Therefore, the proposed method was successfully applied for the simultaneous quantitative analysis of ezetimibe and simvastatin in commercial formulations.

Pinaverium Bromide: Development and Validation of Spectrophotometric Methods for Assay and Dissolution Studies.

This study presents the development and validation of UV spectrophotometric methods for the determination of pinaverium bromide (PB) in tablet assay and dissolution studies. The methods were satisfactorily validated according to International Conference on Harmonization guidelines. The response was linear (r2 > 0.99) in the concentration ranges of 2-14 µg/mL at 213 nm and 10-70 µg/mL at 243 nm. The LOD and LOQ were 0.39 and 1.31 µg/mL, respectively, at 213 nm. For the 243 nm method, the LOD and LOQ were 2.93 and 9.77 µg/mL, respectively. Precision was evaluated by RSD, and the obtained results were lower than 2%. Adequate accuracy was also obtained. The methods proved to be robust using a full factorial design evaluation. For PB dissolution studies, the best conditions were achieved using a United States Pharmacopeia Dissolution Apparatus 2 (paddle) at 50 rpm and with 900 mL 0.1 M hydrochloric acid as the dissolution medium, presenting satisfactory results during the validation tests. In addition, the kinetic parameters of drug release were investigated using model-dependent methods, and the dissolution profiles were best described by the first-order model. Therefore, the proposed methods were successfully applied for the assay and dissolution analysis of PB in commercial tablets.

Stability-indicating micellar electrokinetic chromatography technique for simultaneous measurement of delapril and manidipine from a combination drug formulation.

A stability-indicating micellar electrokinetic chromatography (MEKC) method was developed and validated for simultaneous analysis of delapril (DEL) and manidipine (MAN) using salicylic acid as an internal standard. The MEKC method was performed using a fused-silica capillary (effective length of 72 cm) with 50 mM of borate buffer and 5 mM of anionic surfactant sodium dodecylsulfate at pH 9.0 as the background electrolyte. The separation was achieved at 25 kV applied voltage and 35 degrees C. The injection was performed at 50 mbar for 5 s, with detection at 208 nm. The method was linear in the range of 15-150 microg/mL (r2 = 0.9966) for DEL and 5-50 microg/mL (r2 = 0.9985) for MAN with adequate results for the precision (< or = 1.87%) and accuracy (98.94% for DEL and 100.65% for MAN). The specificity of the method and its stability-indicating capability was demonstrated through forced degradation studies, which showed that there was no interference from the excipients. The Plackett-Burman experimental design was used for robustness evaluation, giving results within the acceptable range. The method was successfully applied for analysis of the drugs, and the results were compared to an LC method, resulting in nonsignificant differences (P = 0.78 and 0.84 for DEL and MAN, respectively).

Formulation development and stability studies of norfloxacin extended-release matrix tablets.

The aim of this research was to develop a new hydrophilic matrix system containing norfloxacin (NFX). Extended-release tablets are usually intended for once-a-day administration with benefits to the patient and lower discontinuation of the therapy. Formulations were developed with hydroxypropylmethylcellulose or poly(ethylene oxide) as hydrophilic polymers, with different molecular weights (MWs) and concentrations (20 and 30%). The tablets were found to be stable (6 months at 40 ± 2°C and 75 ± 5% relative humidity), and the film-coating process is recommended to avoid NFX photodegradation. The dissolution profiles demonstrated an extended-release of NFX for all developed formulations. Dissolution curves analyzed using the Korsmeyer exponential equation showed that drug release was controlled by both drug diffusion and polymer relaxation or erosion mechanisms. A more erosion controlled system was obtained for the formulations containing lower MW and amount of polymer. With the increase in both MW and amount of polymer in the formulation, the gel layer became stronger, and the dissolution was more drug-diffusion dependent. Formulations containing intermediate MW polymers or high concentration (30%) of low MW polymers demonstrated a combination of extended and complete in vitro drug release. This way, these formulations could provide an increased bioavailability in vivo.

Micellar electrokinetic chromatographic method for mianserin hydrochloride and analysis of degradation products by mass spectrometry.

A simple, stability-indicating micellar electrokinetic chromatography (MEKC) method was developed and validated for the analysis of mianserin hydrochloride in coated tablets. The method employed (hydroxymethyl)aminomethane (TRIS) 50 mM to which sodium dodecyl sulfate (SDS) 50 mM was added at pH 10.6 as the electrolyte and the voltage applied was 25 kV. The capillary used was 48.5 cm long (40.0 cm effective length and 50.0 µm i.d.) and the detection wavelength was 220 nm. Tetracycline was used as internal standard. The method was validated in accordance with the International Conference on Harmonization (ICH) requirements, which involved specificity, linearity, precision, accuracy and robustness. The stability-indicating capability of the method was established by enforced degradation studies combined with peak purity assessment using photodiode array detection. The degradation products formed under photolytic and oxidative conditions were investigated by electrospray ionization mass spectrometry. The method was linear over the concentration range of 50-130 µg/mL. The method was precise as demonstrated by an inter-day and intra-day relative standard deviation of less than 2.0%. The proposed validated MEKC method showed recoveries between 98.16 and 102.80% of the nominal contents. The Plackett-Burman design was applied for the robustness test in order to examine potential sources of variability by screening a large number of factors in a relatively small number of experiments.

Delapril and manidipine measurements by liquid chromatography-tandem mass spectrometry in a pharmaceutical formulation.

A simple, specific, fast and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the simultaneous analysis of delapril (DEL) and manidipine (MAN) from their combination formulation was developed and validated using fesoterodine as the internal standard (IS). The LC-MS/MS method was carried out on a Luna C8 column (50 × 3.0 mm i.d., 3 µm) with a mobile phase consisting of methanol and 10 mmol L(-1) ammonium acetate (90 : 0, v/v), run at a flow rate of 0.25 mL min(-1). The mass spectrometry method was performed employing positive electrospray ionization operating in multiple reaction monitoring mode, monitoring the transitions of m/z 453.1 → 234.1 for DEL, m/z 611.1 → 167.0 for MAN and m/z 412.2 → 223.0 for IS. The total analysis time was 3 min and the method was linear in the concentration range of 6-1080 ng mL(-1) and 2-360 ng mL(-1) for DEL and MAN, respectively. Parameters investigated for the method validation, such as the specificity, linearity, precision, accuracy and robustness, gave results within the acceptable range. Moreover, the proposed method was successfully applied for the simultaneous determination of DEL and MAN and the results were compared to validated liquid chromatography and capillary electrophoresis methods showing non-significant differences (P = 0.9).

Determination of fluticasone propionate in nasal sprays by a validated stability-indicating MEKC method.

A micellar electrokinetic chromatography method (MEKC) is developed and validated for the analysis of fluticasone propionate (FP) in nasal sprays. The MEKC method is performed on a fused-silica capillary (50 mum i.d.; effective length, 40 cm). The background electrolyte consists of 25 mM borate and 25 mM anionic detergent SDS solution at pH 9. The capillary temperature is maintained at 35 degrees C, and the applied voltage is 20 kV. The injection is performed using the hydrodynamic mode at 50 mbar for 6 s with detection at 238 nm. The method is linear in the range of 2-80 mug/mL (r(2) = 0.9956). The specificity and stability-indicating capability are proven through forced degradation studies inclusive by mass spectrometry, which also shows that there is no interference of the excipients. The limit of detection and limit of quantitation are 0.56 and 2 mug/mL, respectively. Moreover, method validation demonstrates acceptable results for accuracy, precision, and robustness. The proposed method was successfully applied for the quantitative analysis of FP nasal sprays, and the results were compared to a validated reversed-phase liquid chromatographic method, showing non-significant difference (P > 0.05).

Validation of a stability-indicating RP-HPLC method for the determination of entecavir in tablet dosage form.

An RP-HPLC method was validated for the determination of entecavir in tablet dosage form. The HPLC method was carried out on a Gemini C18 column (150 x 4.6 mm id) maintained at 30 degrees C. The mobile phase consisted of acetonitrile-water (95 + 5, v/v)/potassium phosphate buffer (0.01 M, pH 4; 9 + 91, v/v) pumped at a flow rate of 1.0 mL/min. Photodiode array detection was at 253 nm. The chromatographic separation was obtained with a retention time of 4.18 min, and the method was linear in the range of 0.5-200 microg/mL (r2 = 0.9998). The specificity and stability-indicating capability of the method was proven through forced degradation studies, which also showed that there was no interference of the excipients and an increase of the cytotoxicity only by the basic condition. The accuracy was 101.19%, with bias lower than 1.81%. The LOD and LOQ were 0.39 and 0.5 microg/mL, respectively. Method validation demonstrated acceptable results for precision and robustness. The proposed method was applied for the analysis of tablet formulations, to improve QC and assure therapeutic efficacy.

A high-throughput liquid chromatography tandem mass spectrometry method for the comparative determination of fluticasone propionate by reversed-phase liquid chromatography and capillary electrophoresis methods in pharmaceutical nasal sprays.

A simple, specific, rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the analysis of fluticasone propionate (FP) in pharmaceutical formulations was developed and validated using deflazacort as internal standard (IS). The LC-MS/MS method was carried out on a C8 column (50 mm) with a mobile phase consisted of methanol : water (95 : 5, v/v) 100 mM formic acid-50 mM ammonium acetate (90 : 5 : 5, v/v/v). The mass spectrometry method was performed employing positive atmospheric pressure chemical ionization technique, operating in multiple reaction monitoring mode. The chromatographic separation was obtained within 1.5 min and it was linear in the concentration range of 10-1000 ng mL(-1). Moreover, method validation demonstrates acceptable results for the specificity, accuracy, precision and robustness. The proposed method was successfully applied for the quantitative analysis of FP nasal sprays and the results were compared to validated liquid chromatography and capillary electrophoresis methods with photodiode array detectors showing non-significant difference (P > 0.05).

Validation of a capillary zone electrophoresis method for the comparative determination of etoricoxib in pharmaceutical formulations.

A CZE method was developed and validated for the analysis of etoricoxib in pharmaceutical dosage forms, using prilocaine as an internal standard. The CZE method was carried out on a fused-silica capillary (50 microm id, effective length 40 cm). The BGE consisted of 25 mM tris-phosphate solution at pH 2.5. The capillary temperature was maintained at 35 degrees C, the applied voltage was 25 kV, the injection was performed using the pressure mode at 50 mbar for 5 s, with detection at 234 nm using a photodiode array detector. The method was linear in the range of 2-150 microg/mL (r(2) = 0.9999). The specificity and stability-indicating capability were proven through the degradation studies and showing also that there was no interference of the excipients of the formulation. The accuracy was 99.49% with RSD of 0.66%. The limits of quantitation and detection were 2 and 0.58 microg/mL, respectively. Moreover, method validation demonstrated acceptable results for the precision, sensitivity, and robustness. The proposed method was successfully applied for the quantitative analysis of etoricoxib pharmaceutical formulations, and the results compared to the HPLC and LC-MS/MS methods, showing nonsignificant difference (p >0.05).