Preparation and characterization of two new forced degradation products of letrozole and development of a stability-indicating RP-LC method for its determination.

Two new hydrolytic products of letrozole were identified and proved to be true degradation products obtained by alkaline and acidic degradation of the drug. The acid and amide forms of the nitrile groups of letrozole were prepared and identified by IR and mass spectroscopic techniques. Subsequently, a simple, precise and selective stability-indicating RPLC method was developed and validated for the determination of letrozole in the presence of its degradation products. Letrozole was subjected to alkali and acid hydrolysis, oxidation, thermal degradation and photo-degradation. The degradation products were well isolated from letrozole. The chromatographic method was achieved using gradient elution of the drug and its degradation products on a reversed phase Zorbax Eclipse C18 column (100mm x 4.6mm, 3.5 µm) using a mobile phase consisting of 0.01M KH2PO4and methanol at a flow rate of 1 mL min⁻¹. Quantitation was achieved with UV detection at 230 nm. Linearity, accuracy and precision were found to be acceptable over the concentration range of 0.01-80 µgmL⁻¹. The proposed method was successfully applied to the determination of letrozole in bulk, plasma and in its pharmaceutical preparation.

DoE Screening and Optimization of Liquid Chromatographic Determination of Nicotinic Acid and Six Statins: Application to Pharmaceutical Preparations and Counterfeit Detection.

An isocratic reversed-phase high performance liquid chromatographic method has been developed and validated to simultaneously determine nicotinic acid, pravastatin sodium, rosuvastatin calcium, atorvastatin calcium, pitavastatin calcium, lovastatin sodium and simvastatin sodium in focus on counterfeit drug detection. Thin-layer chromatography, nuclear magnetic resonance and mass spectrometry have been additionally performed to verify the identification of adulterants of counterfeit herbal medicines. Chromatographic separation was carried out on Inertsil® ODS-3 C18 (4.6 × 150 mm, 5 µm) with isocratic mobile phase elution containing a mixture of acetonitrile: methanol: 25 mM potassium dihydrogen phosphate buffer, pH 2.86 adjusted with 0.1 M o-phosphoric acid (48: 30: 22, v/v/v), at a flow rate of 1 mL/min and with UV detection at 238 nm. The design of experiment methodology, Plackett-Burman and Box-Behnken designs, was used to screen and optimize the mobile phase composition. The validation of the method was also carried out under the International Conference on Harmonization guidelines. The developed method was sensitive, accurate, simple, economical and highly robust, in addition to the comprehensiveness and novelty of this method for separating the seven drugs. The results were statistically compared with the reference methods used Student's t-test and variance ratio F-test at P < 0.05.

Validated spectrophotometric methods for the simultaneous determination of ciprofloxacin hydrochloride and metronidazole in tablets.

A binary mixture of ciprofloxacin hydrochloride (CIP) and metronidazole (MET) was determined by five simple and accurate methods, without prior separation. In the first method, CIP was determined by second derivative spectrophotometric method ((2)D) by measuring the amplitude at 282 nm (zero ordinate value of MET). On the other hand, the determination of MET was based on isosbestic point technique, where the total content of the mixture was determined at 294.5 nm (isosbestic point), then the content of MET could be calculated by subtraction. The second method was first derivative ratio spectrophotometric method ((1)DD) where the total amplitude at 261 and 285 nm and the amplitude at 295.5 nm were selected to simultaneously determine CIP and MET in binary mixture, respectively. The third method was based on dual wavelength analysis, in which two wavelengths were selected, at which the absorbances of the other component were the same. The fourth method depends on using Q-analysis method (absorbance ratio) which involves the formation of Q-absorbance equation using the respective absorptivity values at 294.5 nm (isosbestic point) and 281.5 nm (λ(max) of CIP). The fifth method is partial least-squares (PLS) chemometric technique for determination of CIP and MET. The developed methods were successfully applied to the analysis of CIP and MET in laboratory prepared mixtures and tablets with good recoveries and their validation was carried out following the International Conference on Harmonization (ICH) guidelines. The results obtained were statistically compared with each other showing no significant difference with respect to accuracy and precision.

Analysis of Aspirin, Prasugrel and Clopidogrel in Counterfeit Pharmaceutical and Herbal Products: Plackett-Burman Screening and Box-Behnken Optimization.

An isocratic reversed-phase high-performance liquid chromatographic method has been developed and validated for the simultaneous determination of aspirin, prasugrel HCl and clopidogrel bisulfate in the presence of clopidogrel-related compound (impurity-A) in focus on counterfeit. This method was used to determine counterfeited antiplatelet drugs in two substandard Indian pharmaceutical products sold on the market in Yemen and two traditional herbal medicines sold on the market in China. Thin layer chromatography and mass spectrometry of counterfeit herbal medicines have additionally been carried out to verify the identification of adulterants. Chromatographic separation was performed on Inertsil ® ODS-3 C18 (4.6 × 250 mm, 5 µm) with isocratic mobile phase elution containing a mixture of acetonitrile: (25 mM) potassium dihydrogen phosphate buffer, pH 2.7 adjusted with 0.1 M o-phosphoric acid (79: 21, v/v), at a flow rate of 1 mL/min and UV detection at 220 nm. Designs of experiment methodology, Plackett-Burman and Box-Behnken designs were used for the screening and optimization of the mobile phase composition. The method validation was also performed in accordance with the International Council on Harmonization (ICH) guidelines. The method developed for routine analysis was found to be sensitive, simple, accurate and highly robust. The results were statistically compared to reference methods using Student's t-test and variance ratio F-test at P < 0.05.

Analysis of Metformin and Five Gliptins in Counterfeit Herbal Products: Designs of Experiment Screening and Optimization.

BACKGROUND: Drug counterfeiting is a rising problem due to difficulties with identifying counterfeit drugs and the lack of regulations and legislation in developing countries. OBJECTIVE: This study aims to develop a robust and economic reversed phase high performance liquid chromatography (LC) method for simultaneously determining metformin HCl, vildagliptin, saxagliptin, alogliptin benzoate, sitagliptin phosphate monohydrate, and linagliptin to target counterfeiting. METHODS: Plackett-Burman (PB) and Box-Behnken (BB) designs were used to screen and optimize the mobile phase composition. Chromatographic separation was carried out on an Inertsil® ODS-3 C18 column with isocratic elution mode and the mobile phase was a mixture of acetonitrile-methanol-ammonium formate buffer, pH 3.5 (25:10:65, v/v/v). This method was applied to analyze synthetic drugs in three traditional Chinese and Indian herbal medicines. To identify the adulterants, thin-layer chromatography (TLC), nuclear magnetic resonance (NMR), and mass spectrometry (MS) were used on counterfeit herbal medicines. RESULTS: The developed method is sensitive, simple, rapid, economical, accurate, and highly robust. Student's t-test and variance ratio (F-test at P < 0.05) were used to compare the results statistically with the reference methods. CONCLUSION: The study found that the analyzed herbal medicines were adulterated with metformin and the quantification of anti-diabetic counterfeits was therefore applied. HIGHLIGHTS: This study determined counterfeited anti-diabetic drugs in Indian and Chinese traditional herbal medicines(THMs). Design-of-experiment, PB, and BB designs were used. Method validation was also performed in accordance with the International Conference on Harmonization guidelines.