Green quality by design HPLC approach for the simultaneous determination of Bilastine and Montelukast.

For the simultaneous estimation of two co-formulated antihistaminic drugs (Bilastine and Montelukast), a novel and eco-friendly reversed-phase HPLC approach with both diode array and fluorescence detection modes was designed. Rather than using the routine methodology, the Quality by Design (QbD) approach was adopted to speed up the method development and to test robustness of the method. To evaluate the effect of variable factors on chromatographic response, a full factorial design was used. The chromatographic separation was performed using isocratic elution on the C18 column. The mobile phase consists of 92% methanol, 6% acetonitrile, and 2% phosphate buffer with 0.1 (v/v) triethylamine adjusted to pH 3, it was pumped at a flow rate of 0.8 mL/min with an injection volume of 20 µL. The developed stability indicating HPLC approach was used to assess the stability of montelukast (MNT). It was subjected to a variety of stress conditions, including hydrolytic (acid-base), oxidative, thermal, and photolytic stress conditions. All of these conditions were found to have relevant degradation pathways. Under the described experimental conditions, MNT degradation followed pseudo-first-order kinetics. The kinetic parameters of its degradation (rate constant and t1/2) were calculated and a proposal for the degradation pathway was postulated.

A Design-assisted Spectrofluorometric Method Utilizing a One-pot Fluorescent Probe for the Quantitation of some Calcium Channel Blockers.

Based on their reaction with highly fluorescent carbon quantum dots (CQDts), a precise and reliable spectrofluorometric approach was developed for the determination of three calcium channel blockers. The studied drugs are: lercanidipine, nimodipine and nifedipine. (CQDts) were produced using a one-step hydrothermal method with ascorbic acid as the carbon source. The produced CQDts were capped by alcohol to create yellow emitters displaying a high fluorescence emission at 524 nm when excited at 325 nm. The fluorescence intensity of CQDts was noticeably quenched by each of the three calcium channel blockers. The relation between their concentrations and fluorescence quenching is linear over the concentration range of 0.5-20 µg/mL for each of the three drugs. A full factorial design was used to optimize the effect of variable factors. Therefore, under optimum experimental design conditions, the detection limits for lercanidipine, nimodipine, and nifedipine were 0.11 ± 1.09, 0.10 ± 0.25 and 0.12 ± 0.71 µg/mL, respectively. The LOQ was 0.33, 0.30, and 0.37 µg/mL respectively. The quenching of fluorescent CQDts occurred through the inner filter effect (IFE) for nimodipine, while it was mixed with dynamic quenching for lercanidipine and nifedipine. The proposed method was effectively used to determine the cited drugs in their pharmaceutical products and had an acceptable level of precision. The selectivity of the CQDts system towards the studied drugs was examined indicating no interference from interfering species.

Effect of low-energy shock wave therapy on intravesical epirubicin delivery in a rat model of bladder cancer.

OBJECTIVES: To study the efficacy of low-energy shock wave therapy (LESW) on enhancing intravesical epirubicin (EPI) delivery in a rat model of bladder cancer (BCa). MATERIALS AND METHODS: A total of 100 female Fischer rats were randomly allocated into five groups: control; BCa; LESW; EPI; and EPI plus LESW. After BCa induction by N-butyl-N-(4-hydroxybutyl)nitrosamine, EPI (0.6 mg/0.3 mL of EPI diluted in 0.3 mL saline) or saline (0.6 mL) was administered and retained in the bladders for 1 h with or without LESW treatment (300 pulses at 0.12 mJ/mm2 ). This was repeated weekly for 6 weeks. Survival was then calculated, rats were weighed and their bladders were harvested for bladder/body ratio estimation, histopathological examination, p53 immunostaining, miR-210, hypoxia-inducible factor (HIF)-1α, tumour necrosis factor (TNF)-α and interleukin (IL)-6 relative gene expression and fluorescence spectrophotometric drug quantification. Heart and blood samples were also collected for assessment of the safety profile and toxicity. RESULTS: The EPI plus LESW group had significantly lower mortality rates, loss of body weight and bladder/body ratio. Histopathological results in terms of grossly visible bladder lesions, mucosal thickness, dysplasia formation and tumour invasion were significantly better in the combined treatment group. The EPI plus LESW group also had statistically significant lower expression levels of p53 , miR-210, HIF-1α, TNF-α and IL-6. LESW increased urothelial concentration of EPI by 5.7-fold (P < 0.001). No laboratory variable exceeded the reference ranges in any of the groups. There was an improvement of the indicators of EPI-induced cardiomyopathy in terms of congestion, hyalinization and microvesicular steatosis of cardiomyocytes (P = 0.068, 0.003 and 0.046, respectively) in the EPI plus LESW group. CONCLUSIONS: The combined use of intravesical EPI and LESW results in less BCa invasion and less dysplasia formation, as LESW increases urothelial permeability of EPI and enhances its delivery into tumour tissues, without subsequent toxicity.

Simultaneous determination of sitagliptin and metformin in pharmaceutical preparations by capillary zone electrophoresis and its application to human plasma analysis.

A novel, quick, reliable and simple capillary zone electrophoresis CZE method was developed and validated for the simultaneous determination of sitagliptin (SG) and metformin (MF) in pharmaceutical preparations. Separation was carried out in fused silica capillary (50.0 cm total length and 43.0 cm effective length, 49 µm i.d.) by applying a potential of 15 KV (positive polarity) and a running buffer containing 60 mM phosphate buffer at pH 4.0 with UV detection at 203 nm. The samples were injected hydrodynamically for 3 s at 0.5 psi and the temperature of the capillary cartridge was kept at 25 °C. Phenformin was used as internal standard (IS). The method was suitably validated with respect to specificity, linearity, limit of detection and quantitation, accuracy, precision, and robustness. The method showed good linearity in the ranges of 10-100 µg/mL and 50-500 µg/mL with limits of detection of 0.49, 2.11 µg/mL and limits of quantification of 1.48, 6.39 µg/mL for SG and MF, respectively. The proposed method was successfully applied for the analysis of the studied drugs in their synthetic mixtures and co-formulated tablets without interfering peaks due to the excipients present in the pharmaceutical tablets. The method was further extended to the in-vitro determination of the two drugs in spiked human plasma. The estimated amounts of SG/MF were almost identical with the certified values, and their percentage relative standard deviation values (% R.S.D.) were found to be ≤1.50% (n = 3). The results were compared to a reference method reported in the literature and no significant difference was found statistically.

Synchronous fluorescence spectrofluorimetric method for the simultaneous determination of metoprolol and felodipine in combined pharmaceutical preparation.

A rapid, simple and sensitive synchronous specrtofluorimetric method has been developed for the simultaneous analysis of binary mixture of metoprolol (MTP) and felodipine (FDP). The method is based upon measurement of the synchronous fluorescence intensity of the two drugs at Δλ of 70 nm in aqueous solution. The different experimental parameters affecting the synchronous fluorescence intensities of the two drugs were carefully studied and optimized. The fluorescence intensity-concentration plots were rectilinear over the ranges of 0.5-10 µg/mL and 0.2-2 µg/mL for MTP and FDP, respectively. The limits of detection were 0.11 and 0.02 µg/mL and quantification limits were 0.32 and 0.06 µg/mL for MTP and FDP, respectively. The proposed method was successfully applied for the determination of the two compounds in their commercial tablets and the results obtained were favorably compared to those obtained with a comparison method.

Development and validation of stability indicating method for determination of sertraline following ICH guidlines and its determination in pharmaceuticals and biological fluids.

BACKGROUND: Sertraline is a well known antidepressant drug which belongs to a class called selective serotonin reuptake inhibitor. Most published methods do not enable studying the stability of this drug in different stress conditions. RESULTS: Two new methods were developed for the determination of sertraline (SER). Both methods are based on coupling with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) in borate buffer of pH 7.8 and measuring the reaction product spectrophotometrically at 395 nm (Method I) or spectrofluorimetrically at 530 nm upon excitation at 480 nm (Method II). The response-concentration plots were rectilinear over the range 2-24 µg/mL and 0.25-5 µg/mL for methods I and II respectively with LOD of 0.18 µg/mL and 0.07 µg/mL, and LOQ of 0.56 µg/mL and 0.21 µg/mL for methods I and II, respectively. CONCLUSION: Both methods were applied to the analysis of commercial tablets and the results were in good agreement with those obtained using a reference method. The fluorimetric method was further applied to the in vivo determination of SER in human plasma. A proposal of the reaction pathway was presented. The spectrophotometric method was extended to stability study of SER. The drug was exposed to alkaline, acidic, oxidative and photolytic degradation according to ICH guidelines. Moreover, the method was utilized to investigate the kinetics of oxidative degradation of the drug. The apparent first order rate constant and t1/2 of the degradation reaction were determined.

Utility of certain nucleophilic aromatic substitution reactions for the assay of pregabalin in capsules.

BACKGROUND: Pregabalin (PG) is an anticonvulsant, analgesic and anxiolytic drug. A survey of the literature reveals that all the reported spectrophotometric methods are either don't offer high sensitivity, need tedious extraction procedures, recommend the measurement of absorbance in the near UV region where interference most probably occurs and/or use non specific reagent that don't offer suitable linearity range. RESULTS: Two new sensitive and simple spectrophotometric methods were developed for determination of pregabalin (PG) in capsules. Method (I) is based on the reaction of PG with 1,2-naphthoquinone-4-sulphonate sodium (NQS), yielding an orange colored product that was measured at 473 nm. Method (II) is based on the reaction of the drug with 2,4-dinitrofluorobenzene (DNFB) producing a yellow product measured at 373 nm. The different experimental parameters affecting the development and stability of the reaction product in methods (I) and (II) were carefully studied and optimized. The absorbance-concentration plots were rectilinear over the concentration ranges of 2-25 and 0.5-8 µg mL-1 for methods (I) and (II) respectively. The lower detection limits (LOD) were 0.15 and 0.13 µg mL-1 and the lower quantitation limits (LOQ) were 0.46 and 0.4 µg mL-1 for methods (I) and (II) respectively. CONCLUSION: The developed methods were successfully applied to the analysis of the drug in its commercial capsules. The mean percentage recoveries of PG in its capsule were 99.11 ± 0.98 and 100.11 ± 1.2 (n = 3). Statistical analysis of the results revealed good agreement with those given by the comparison method. Proposals of the reaction pathways were postulated.