A liquid chromatography (LC) method and an ultraviolet (UV) spectrophotometricmethod were developed and validated for quantitative determination of amlodipine in tablets and compounded capsules. The isocratic LC analyses were performed on an RP18 column using a mobile phase composed of 0.1 (v/v) ortho-phosphoric acid (pH 3.0) acetonitrile (60 40, v/v) at a flow rate of 1.0 mL/min. The UV spectrophotometricmethodwas performed at 238 nm. The analytical methodswere validated according to International Conference on Harmonization Guidelines. The calibration graphswere linear correlation coefficient (r) > 0.999 in the studied concentration range of 1030 g/mL for LC and 1035 g/mL for UV spectrophotometry. The relative standard deviation values for intraday and interday precision studies were less than 2, and the accuracywas greater than 98 for bothmethods. The specificity of the LC method was proved using forced degradation. Statistical analyses showed no significant difference between the results obtained by the 2 methods. The proposed methods are precise and accurate and can be applied directly and easily to the oral pharmaceutical preparations of amlodipine.
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.
Fluoroquinolones are a known antibacterial class commonly used around the world. These compounds present relative stability and they may show some adverse effects according their distinct chemical structures. The chemical hydrolysis of five fluoroquinolones was studied using alkaline and photolytic degradation aiming to observe the differences in molecular reactivity. DFT/B3LYP-6.31G* was used to assist with understanding the chemical structure degradation. Gemifloxacin underwent degradation in alkaline medium. Gemifloxacin and danofloxacin showed more degradation perceptual indices in comparison with ciprofloxacin, enrofloxacin and norfloxacin in photolytic conditions. Some structural features were observed which may influence degradation, such as the presence of five member rings attached to the quinolone ring and the electrostatic positive charges, showed in maps of potential electrostatic charges. These measurements may be used in the design of effective and more stable fluoroquinolones as well as the investigation of degradation products from stress stability assays.
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