Development and validation of a stability-indicating UPLC method for the determination of olmesartan medoxomil, amlodipine and hydrochlorothiazide degradation impurities in their triple-combination dosage form using factorial design of experiments.

The current work describes the development and validation of a stability-indicating UPLC method for the determination of olmesaratan medoxomil (OLM), amlodipine besylate (AMB), hydrochlorothiazide (HCT) and their degradation products in the triple-combination tablet dosage form. The separation was achieved using a Zorbax Eclipse plus C8 RRHD (100 mm × 3.0 mm), 1.8 µm column with gradient elution of mobile phase A containing 0.02 m of sodium phosphate buffer (pH 3.35) and mobile phase B as acetonitrile and water (90:10, v/v). The detector signal was monitored at UV 250 nm. Analytical performance of the optimized UPLC method was validated as per International Conference on Harmonization guidelines. The linearity ranges for OLM, AMB and HCT were 0.59-240, 0.30-60 and 0.37-150 µg/ml, respectively, with correlation coefficients >0.999. The dosage form was subjected to forced-degradation conditions of neutral, acidic and alkaline hydrolysis, oxidation and thermal and photodegradation. The method was proved to be stability indicating by demonstrating the specificity of the drugs from degradation products. The robustness of the method was evaluated through a two-level, three-factorial design with a multivariate approach. Statistical data analysis with best model fit P-value < 0.05 from an ANOVA test indicated that the influence of individual factors is relatively higher than the interaction effects. The method is useful for the analysis of drug products.

Synthesis and Physicochemical Characterization of the Process-Related Impurities of Olmesartan Medoxomil. Do 5-(Biphenyl-2-yl)-1-triphenylmethyltetrazole Intermediates in Sartan Syntheses Exist?

During the process development for multigram-scale synthesis of olmesartan medoxomil (OM), two principal regioisomeric process-related impurities were observed along with the final active pharmaceutical ingredient (API). The impurities were identified as N-1- and N-2-(5-methyl-2-oxo-1,3-dioxolen-4-yl)methyl derivatives of OM. Both compounds, of which N-2 isomer of olmesartan dimedoxomil is a novel impurity of OM, were synthesized and fully characterized by differential scanning calorimetry (DSC), infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (NMR) and high-resolution mass spectrometry/electrospray ionization (HRMS/ESI). Their ¹H, (13)C and (15)N nuclear magnetic resonance signals were fully assigned. The molecular structures of N-triphenylmethylolmesartan ethyl (N-tritylolmesartan ethyl) and N-tritylolmesartan medoxomil, the key intermediates in OM synthesis, were solved and refined using single-crystal X-ray diffraction (SCXRD). The SCXRD study revealed that N-tritylated intermediates of OM exist exclusively as one of the two possible regioisomers. In molecular structures of these regioisomers, the trityl substituent is attached to the N-2 nitrogen atom of the tetrazole ring, and not to the N-1 nitrogen, as has been widely reported up to the present. This finding indicates that the reported structural formula of N-tritylolmesartan ethyl and N-tritylolmesartan medoxomil, as well as their systematic chemical names, must be revised. The careful analysis of literature spectroscopic data for other sartan intermediates and their analogs with 5-(biphenyl-2-yl)tetrazole moiety showed that they also exist exclusively as N-2-trityl regioisomers.

Visualisation of real-time oral biodistribution of fluorescent labeled self-microemulsifying drug delivery system of olmesartan medoxomil using optical imaging method.

In the present study, the biodistribution of self-microemulsifying drug delivery system of hydrophobic olmesartan medoxomil (OM-SMEDDS) was determined by labeling with a fluorescent dye VivoTag®680 XL and Xenolight® DiR. Labeled OM-SMEDDS and control dye solution administered orally to mice; real-time dynamic biodistributions over 7 h were determined by 2D-fluorescent imaging to verify their anatomic location. Fluorescent Emissions by Vivotag 680® XL and Xenolight® DiR labeled OM-SMEDDS emitted 2 to 24 times stronger emission than control dye administered group. To further confirm the results, organs were removed and examined using the same technique at the end of 7 h. VivoTag®680XL and Xenolight® DiR emitted 4 and 1.7 times stronger emission respectively than control dye administered mice in ex-vivo organ imaging studies. This study showed that OM-SMEDDS can be succesfully labeled with fluorescent dye and tracked with optical imaging method for the visualisation of biodistribution of drugs and is also useful for enhanced bioavailability.

Simultaneous Quantitation of Amlodipine Besylate and Olmesartan Medoxomil in Fixed-Dose Combination Tablets: HPLC-DAD Versus UHPLC-DAD.

Association of amlodipine besylate and olmesartan medoxomil in fixed-dose combination tablets is effective, safe and well tolerated for the treatment of hypertension. The aim of this study was to optimize and validate a novel and fast UHPLC-DAD method for simultaneous quantification of these antihypertensive drugs in tablets, using a transfer procedure from a conventional HPLC-DAD method. The HPLC separation was carried out using a C18 column (150 × 4.6 mm2; 5 µm) and a mobile phase composed of acetonitrile, methanol and 0.3% trimethylamine pH 2.75 (30:30:40), at 1.0 mL/min. UV detection was performed at 238 nm and injection volume was 10 µL. Then, the analytical method was transferred to UHPLC, using a BEH C18 column (50 × 2.1 mm2; 1.7 µm). Mathematical equations were applied to calculate the UHPLC mobile phase flow rate and injection volume, which were 0.613 mL/min and 0.7 µL, respectively. UHPLC method was fully validated and showed to be selective, linear (r2 > 0.99), precise (RSD < 2.0%), accurate and robust. UHPLC method was statistically equivalent to the HPLC method after analysis of three batches of BenicarAnlo® tablets. However, UHPLC method promoted faster analyses, better chromatographic performance and lower solvent consumption.

Three-way analysis of the UPLC-PDA dataset for the multicomponent quantitation of hydrochlorothiazide and olmesartan medoxomil in tablets by parallel factor analysis and three-way partial least squares.

An application of parallel factor analysis (PARAFAC) and three-way partial least squares (3W-PLS1) regression models to ultra-performance liquid chromatography-photodiode array detection (UPLC-PDA) data with co-eluted peaks in the same wavelength and time regions was described for the multicomponent quantitation of hydrochlorothiazide (HCT) and olmesartan medoxomil (OLM) in tablets. Three-way dataset of HCT and OLM in their binary mixtures containing telmisartan (IS) as an internal standard was recorded with a UPLC-PDA instrument. Firstly, the PARAFAC algorithm was applied for the decomposition of three-way UPLC-PDA data into the chromatographic, spectral and concentration profiles to quantify the concerned compounds. Secondly, 3W-PLS1 approach was subjected to the decomposition of a tensor consisting of three-way UPLC-PDA data into a set of triads to build 3W-PLS1 regression for the analysis of the same compounds in samples. For the proposed three-way analysis methods in the regression and prediction steps, the applicability and validity of PARAFAC and 3W-PLS1 models were checked by analyzing the synthetic mixture samples, inter-day and intra-day samples, and standard addition samples containing HCT and OLM. Two different three-way analysis methods, PARAFAC and 3W-PLS1, were successfully applied to the quantitative estimation of the solid dosage form containing HCT and OLM. Regression and prediction results provided from three-way analysis were compared with those obtained by traditional UPLC method.

Development and Validation of a Stability-Indicating Liquid Chromatographic Method for Estimating Olmesartan Medoxomil Using Quality by Design.

The current studies entail systematic quality by design (QbD)-based development of a simple, rapid, sensitive and cost-effective stability-indicating method for the estimation of olmesartan medoxomil. Quality target method profile was defined and critical analytical attributes (CAAs) for the reverse-phase liquid chromatography method earmarked. Chromatographic separation accomplished on a C18 column using acetonitrile and water (containing 0.1% orthophosphoric acid, pH 3.5) in 40 : 60 (v/v) as mobile phase at a flow rate of 1.0 mL/min with UV detection at 243 nm. Risk assessment studies and screening studies facilitated comprehensive understanding of the factors affecting CAAs. The mobile phase ratio and flow rate were identified as critical method parameters (CMPs) and were systematically optimized using face-centered cubic design, evaluating for CAAs, namely peak area, retention time, theoretical plates and peak tailing. Statistical modelization was accomplished followed by response surface analysis for comprehending plausible interaction(s) among CMPs. Search for optimum solution was conducted through numerical and graphical optimization for demarcating the design space. Analytical method validation and subsequent forced degradation studies corroborated the method to be highly efficient for routine analysis of drug and its degradation products. The studies successfully demonstrate the utility of QbD approach for developing the highly sensitive liquid chromatographic method with enhanced method performance.