Ezetimibe: A Review of Analytical Methods for the Drug Substance, Pharmaceutical Formulations and Biological Matrices

Ezetimibe (EZM) is a selective inhibitor of the sterol transporter Niemann-Pick C1-Like 1 in the small intestine used as an adjunctive therapy to lower cholesterol levels in cases of hyperlipidemia. The goal of this work was to summarize the main physical-chemical, pharmacological and pharmacokinetic characteristics of EZM, as well as to describe the main analytical methodologies for the quantification of the drug. Methods described in the United States Pharmacopeia for EZM raw material and tablets were also presented. The drug has a large number of process-related impurities and degradation products and needs strict quality control of its impurities. Specific chiral methods for the evaluation of its chiral impurities are also a need for EZM. The main advantages and disadvantages of the compiled analytical methods were presented, as well as the limits of detection and quantitation. The fastest and most efficient methods were highlighted. Most methods for analyzing EZM used C₈ or C₁₈ stationary phases in gradient mode with binary mobile phases containing acetonitrile and an acidic buffer solution with ultraviolet detection. For analysis of EZM in biological matrices, liquid chromatography-tandem mass spectrometry is generally employed using electron spray ionization in negative ionization mode using multiple reaction monitoring. Different methods in the literature evaluate a large number of impurities for EZM, however new stability-indicating high-performance liquid chromatography methods for the drug are still needed.

Microemulsion liquid chromatographic method for simultaneous determination of simvastatin and ezetimibe in their combined dosage forms

A rapid HPLC procedure using a microemulsion as an eluent was developed and validated for analytical quality control of antihyperlipidemic mixture containing simvastatin (SIM) and ezetimibe (EZT) in their pharmaceutical preparations. The separation was performed on a column packed with cyano bonded stationary phase adopting UV detection at 238 nm using a flow rate of 1 mL/min. The optimized microemulsion mobile phase consisted of 0.2 M sodium dodecyl sulphate, 1% octanol, 10% n-propanol, and 0.3% triethylamine in 0.02 M phosphoric acid at pH 5.0. The developed method was validated in terms of specificity, linearity, lower limit of quantification (LOQ), lower limit of detection (LOD), precision, and accuracy. The proposed method is rapid (8.5 min), reproducible (RSD < 2.0%) and achieves satisfactory resolution between SIM and EZT (resolution factor = 2.57). The mean recoveries of the analytes in pharmaceutical preparations were in agreement with those obtained from a reference method, as revealed by statistical analysis of the obtained results using Student's t-test and the variance ratio F-test.

Two spectrophotometric methods for simultaneous determination of some antihyperlipidemic drugs

Two simple, accurate, precise and economic spectrophotometric methods have been developed for simultaneous determination of Atorvastatin calcium (ATR) and Ezetimibe (EZ) in their bulk powder and pharmaceutical dosage form. Method (I) is based on dual wavelength analysis while method (II) is the mean centering of ratio spectra spectrophotometric (MCR) method. In method (I), two wavelengths were selected for each drug in such a way that the difference in absorbance was zero for the second drug. At wavelengths 226.6 and 244 nm EZ had equal absorbance values; therefore, these two wavelengths have been used to determine ATR; on a similar basis 228.6 and 262.8 nm were selected to determine EZ in their binary mixtures. In method II, the absorption spectra of both ATR and EZ with different concentrations were recorded over the range 200-350, divided by the spectrum of suitable divisor of both ATR and EZ and then the obtained ratio spectra were mean centered. The concentrations of active components were then determined from the calibration graphs obtained by measuring the amplitudes at 215-260 nm (peak to peak) for both ATR and EZ. Accuracy and precision of the developed methods have been tested; in addition recovery studies have been carried out in order to confirm their accuracy. On the other hand, selectivities of the methods were tested by application for determination of different synthetic mixtures containing different ratios of the studied drugs. The developed methods have been successfully used for determination of ATR and EZ in their combined dosage form and statistical comparison of the developed methods with the reported spectrophotometric one using F and Student's t-tests showed no significant difference regarding both accuracy and precision.

Ezetimibe

Ezetimibe is a drug substance which can be used for lowering low-density lipoprotein cholesterol. Its crystal form and polymorphism have been determined using X-ray diffraction and thermal methods. Quantitative and qualitative analysis of Ezetimibe as well as study of its impurities and degradations were summarized in this chapter.