LC-MS/MS method for simultaneous estimation of candesartan and hydrochlorothiazide in human plasma and its use in clinical pharmacokinetics

Sustainable chromatographic quantitation of multi-antihypertensive medications: application on diverse combinations containing hydrochlorothiazide along with LC-MS/MS profiling of potential impurities: greenness and whiteness evaluation

Cardiovascular disorders are among the leading causes of death worldwide, especially hypertension, a silent killer syndrome requiring multiple drug therapy for appropriate management. Hydrochlorothiazide is an extensively utilized thiazide diuretic that combines with several antihypertensive drugs for effective treatment of hypertension. In this study, sustainable, innovative and accurate high performance liquid chromatographic methods with diode array and tandem mass detectors (HPLC-DAD and LC-MS/MS) were developed, optimized and validated for the concurrent determination of Hydrochlorothiazide (HCT) along with five antihypertensive drugs, namely; Valsartan (VAL), Amlodipine besylate (AML), Atenolol (ATN), Amiloride hydrochloride (AMI), and Candesartan cilextil (CAN) in their diverse pharmaceutical dosage forms and in the presence of Chlorothiazide (CT) and Salamide (DSA) as HCT officially identified impurities. The HPLC-DAD separation was achieved utilizing Inertsil ODS-3 C18 column (250 × 4.6 mm, 5 μm) attached with photodiode array detection at 225.0 nm. Gradient elution was performed utilizing a mixture of solvent A (20.0 mM potassium dihydrogen phosphate, pH 3.0 ± 0.2, adjusted with phosphoric acid) and solvent B (acetonitrile) at ambient temperature. Linearity ranges were 0.1-100.0 µg/mL for HCT, VAL, AML and CAN, 0.05 -100.0 µg/mL for both ATN and AMI and 0.05-8.0 µg/mL for both CT and DSA. Additionally, this work describes the use of liquid chromatography-electrospray-tandem mass spectrometry for the accurate detection and quantification of the impurities; CT and DSA in the negative mode utilizing triple quadrupole mass spectrometry. The linearity ranges for those impurities were 1.0-200.0 ng/mL and 5.0-200.0 ng/mL for CT and DSA, respectively. Developed methods' validation was achieved in accordance with International Conference on Harmonization (ICH) guidelines. Upon applying liquid chromatographic techniques for the drug analysis, a green and sustainable assessment have to be handled due to the consumption of energy and many solvents. Through the use of the HEXAGON, Analytical Greenness (AGREE) and White Analytical Chemistry (WAC) tools, greenness and sustainability have been statistically assessed. The optimized HPLC-DAD and LC-MS/MS methods were fast, accurate, precise, and sensitive, and consequently could be applied for conventional analysis and quality control of the proposed drugs in their miscellaneous dosage forms for the purpose of reducing laboratory wastes, time of the analysis time, effort, and cost.

Chemometric Methods for Simultaneous Determination of Candesartan Cilexetil and Hydrochlorothiazide in Binary Combinations

Simple, accurate, precise, and cost-effective chemometric techniques for the measurement of candesartan cilexetil and hydrochlorothiazide in synthetic mixtures were improved and validated. H-point standard addition, Q-absorption ratio, and correction absorbance spectrophotometric techniques were utilized for the simultaneous determination of both medicines in real pharmaceutical formulations. A new calibration approach was implemented based on chemical H-point standards. This approach was developed to resolve significantly overlapping spectra of two analytes and provide direct correction of both proportional and constant errors caused by the matrix of the sample. The first method of simultaneous determination of candesartan cilexetil and hydrochlorothiazide was carried out using the H-point standard addition method at wavelengths 239 and 283. For the ratio of the absorption at two selected wavelengths, one of which is the isoabsorptive point and the other being the maximum of one of the two components, the second method absorption ratio method was utilized. In distilled water, the isoabsorptive point of candesartan cilexetil and hydrochlorothiazide occurs at 258 nm. λ _max of hydrochlorothiazide is 273 nm, which is the second wavelength used. Lastly, the absorbance correction method was implemented. This approach is based on absorbance correction equations and uses distilled water as the solvent for the examination of both medicines. In NaOH/EtOH solvent, the absorbance maxima of candesartan cilexetil and hydrochlorothiazide are 250 nm and 340 nm, respectively. For both wavelengths, candesartan cilexetil and hydrochlorothiazide exhibited linearity over a concentration range of 1-46 μg/ml and 1-44 μg/ml, respectively, for H-point standard addition. The Q-absorption ratio approach provides linearity over the concentration ranges of 1-46 μg/ml at 273 nm for candesartan cilexetil and 1-29 μg/ml for hydrochlorothiazide, 1-46 μg/ml at 258 nm for candesartan cilexetil, and 1-44 μg/ml for hydrochlorothiazide. For hydrochlorothiazide, the linearity for the correction absorbance method was obtained throughout a concentration range of 1-46 μg/ml at wavelengths 250 and 340 nm and 1-44 μg/ml at wavelength 250 nm. The results of the analysis have been statistically and empirically supported by recovery studies. All methods yielded recoveries in the range of 96 -102% for both medications. The LOD ranged from 0.46 -0.94 μg/mL for hydrochlorothiazide and from 1.26 -2.40 μg/mL for candesartan cilexetil. The approaches were then used to quantify candesartan cilexetil and hydrochlorothiazide in pharmaceutical tablets.

Sustainable spectrophotometric determination of antihypertensive medicines reducing COVID-19 risk via paired wavelength data processing technique - Assessment of purity, greenness and whiteness

Recent studies have reported that using certain antihypertensive therapies such as angiotensin II receptor blockers (ARBs) is associated with mitigation of fatal outcomes and enhancing clinical features of patients having hypertension during coronavirus pandemic. Thus, in the current work an innovative, effective, white and sustainable spectrophotometric technique called paired wavelength data processing technique (PWDPT) was developed for evaluation of recommended antihypertensive combination therapies incorporating candesartan cilexetil (CAN) and hydrochlorothiazide (HCT). This technique included three methods, namely, absorbance resolution (AR), amplitude resolution (PR) and ratio extraction (RE). Linearity ranges were (5.0 μg/mL - 50.0 μg/mL) and (2.0 μg/mL - 24.0 μg/mL) for CAN and HCT, respectively. Validation and confirmation of all suggested methods were conducted in accordance with ICH guidelines, producing satisfactory results within the accepted limits. Statistical comparison was achieved between the attained results from suggested methods and those attained from official methods, in which insignificant difference was existed. The suggested methods were successfully employed for identification of the studied drugs as well as determination of their spectral recognition and evaluation of the purity in their combined formulations. The proposed methods followed the principles of green analytical chemistry, where their greenness was evaluated and compared with the official potentiometric and HPLC methods via using four tools, namely, National Environmental Methods Index (NEMI), the Analytical Eco-Scale, the Green Analytical Procedure Index (GAPI) and Analytical greenness metric (AGREE) which affirmed the eco-friendly nature of the proposed methods. Moreover, studying the whiteness features was performed using the recently introduced RGB12 model. The acceptable results along with the sustainability, simplicity, affordability and low-cost of the proposed methods encourages their utilization in the quality control laboratories.

Determination of candesartan or olmesartan in hypertensive patient plasma using UPLC-MS/MS

Candesartan and olmesartan are angiotensin II receptor blockers (ARBs) used for the treatment of hypertension and heart failure. Quantitation methods for candesartan and olmesartan were developed using ultra-high performance liquid chromatography-tandem mass spectrometry following protein precipitation. Candesartan was separated using 5 mM ammonium formate (A) and 100% acetonitrile (B) and olmesartan was separated using 2 mM ammonium formate with 0.1% formic acid (A) and 100% acetonitrile (B). Separation was performed using an isocratic method with a Thermo hypersil GOLD C18 column. Electrospray ionization was used for analyte ionization and detection of candesartan, olmesartan, and the internal standards by multiple reaction monitoring. Developed method showed excellent linearity (r > 0.99) in the concentration range of 2-500 ng/mL for candesartan and 5-2,500 ng/mL for olmesartan. Accuracies were 86.70-108.8% for candesartan and 87.87-112.6% for olmesartan. These methods were able to successfully measure plasma candesartan or olmesartan concentrations in hypertensive patients. This study can be used for pharmacokinetic studies of candesartan or olmesartan in humans.

Application of supercritical fluid chromatography for separation and quantitation of 15 co-formulated binary anti-hypertensive medications using a single elution protocol

A facile supercritical fluid chromatography method is proposed to analyse 15 co-formulated binary anti-hypertensive drug combinations using a customized elution procedure. The effect of mobile phase composition, column back pressure and temperature was suitably optimized for adequate retention, analyte response and resolution. The chromatographic separation of the different drug combinations was performed on a DCPak poly(4-vinylpyridine) column (250 × 4.6 mm, 5 μm) at 125-bar pressure and 40°C using a photodiode array detector. A linear gradient of CO₂ and 0.1% formic acid in methanol provided the best elution conditions for all drug combinations. Baseline separation of the drugs was possible with resolution factor R_s ranging from 1.42 to 12.58. The method was validated for specificity, sensitivity, accuracy and precision, recovery and robustness. The limit of detection and limit of quantitation for aliskiren, amlodipine, atenolol, candesartan, hydrochlorothiazide, lisinopril, losartan, metoprolol, olmesartan, telmisartan and valsartan were in the range of 0.26-2.56 and 0.77-7.75 μg/mL, respectively. The thermodynamic study revealed that interactions of the drugs with the stationary phase were spontaneous as evident from the negative free energy values, and the separation process was enthalpy driven. The developed method was successfully employed to analyse these drugs in their co-formulated tablet formulations.

Simultaneous quantification of candesartan and irbesartan in rabbit eye tissues by liquid chromatography-tandem mass spectrometry

Diabetic retinopathy is a major cause of vision loss in adults. Novel eye-drop formulations of candesartan and irbesartan are being developed for its cure or treatment. To support a preclinical trial in rabbits, it was critical to develop and validate a new LC-MS/MS method for simultaneous quantification of candesartan and irbesartan in rabbit eye tissues (cornea, aqueous humor, vitreous body and retina/choroid). Eye tissue samples were first homogenized in H₂ O-diluted rabbit plasma. The candesartan and irbesartan in the supernatants together with their respective internal standards (candesartan-d₄ and irbesartan-d₄ ) were extracted by solid-phase extraction. The extracted samples were injected onto a C₁₈ column for gradient separation. The MS detection was in the positive electrospray ionization mode using the multiple reaction monitoring transitions of m/z 441 → 263, 445 → 267, 429 → 207, and 433 → 211 for candesartan, candesartan-d₄ , irbesartan and irbesartan-d₄ , respectively. For the validated concentration ranges (2-2000 and 5-5000 ng/g for candesartan and irbesartan, respectively), the within-run and between-run accuracies (% bias) were within the range of -8.0-10.0. The percentage CV ranged from 0.6 to 7.3. There was no significant matrix interference nor matrix effect from different eye tissues and different rabbits. The validated method was successfully used in the Good Laboratory Practice (GLP) study of rabbits.

Quantitative bio-analysis of pitavastatin and candesartan in rat plasma by HPLC-UV: Assessment of pharmacokinetic drug-drug interaction

A novel, precise, accurate and rapid HPLC-UV method was developed, optimised and fully validated for simultaneous estimation of pitavastatin (PIT) and candesartan (CAN) in rat plasma using telmisartan as an internal standard. Following liquid-liquid extraction of the analytes from plasma, chromatographic separation was accomplished on a Waters Reliant C18 column (4.6 × 250 mm, 5 µm) using ACN-5 mM Sodium acetate buffer (80:20, v/v; pH adjusted to 3.5 with acetic acid) as mobile phase at a flow rate of 0.8 mL/min and wavelength of 234 nm. The calibration curves were linear over the concentration ranges of 2-400 ng/mL and 3-400 ng/mL for pitavastatin and candesartan respectively. The method when validated as per US-FDA guidelines was found to be precise as well as accurate. Extraction recovery observed for both analytes was above 90% as well as reproducible and consistent. Stability studies showed the samples to be stable over a long period covering from sample collection to final analysis. The method was successfully applied to investigate pharmacokinetic interaction between PIT and CAN in wistar rats. The mean plasma concentration-time curves of PIT and CAN showed that single PIT as well as CAN show similar pharmacokinetic properties to those obtained when co-administrated with each other (P value >0.05). Hence, there is no evidence for a potential drug-drug interaction between PIT and CAN. This information provides evidence for clinical rational use of CAN and PIT in cardiovascular patients.

Method Validation for Simultaneous Quantification of Olmesartan and Hydrochlorothiazide in Human Plasma Using LC-MS/MS and Its Application Through Bioequivalence Study in Healthy Volunteers

A new, simple, sensitive, selective, rapid, and high-throughput liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed and validated for simultaneous quantification of Olmesartan and hydrochlorothiazide in human plasma. Simple liquid–liquid extraction procedure was applied for plasma sample pretreatment using a mixture of diethyl ether and dichloromethane, as an extraction solution. Analytes were separated on UNISOL C18 150*4.6 mm, 5 µm column using methanol, and 2 mM ammonium acetate pH 5.5 (80:20, v/v) as a mobile phase and detected by electrospray ionization in the multiple reaction monitoring (MRM) mode. The mass transition ion pairs were followed in negative ion mode as m/z 445.20 → 148.90 for Olmesartan; m/z 451.40 → 154.30 for Olmesartan D₆ and m/z 295.80 → 205.10 for hydrochlorothiazide; m/z 298.90 → 206.30 for hydrochlorothiazide ¹³C D₂. The method showed excellent linearity (r² > 0.99) over the concentration range of 5.002–2,599.934 ng/ml for Olmesartan and from 3.005 to 499.994 ng/ml for hydrochlorothiazide. Precision (% CV) and accuracy (% bias) for Olmesartan were found in the range of 3.07–9.02% and −5.00–0.00%, respectively. Precision (% CV) and accuracy (% bias) for hydrochlorothiazide were found in the range of 3.32–8.21% and 1.99–3.80%, respectively. This as developed novel and high-throughput liquid–liquid extraction bioanalytical method has substantial innovative value with the benefits of cost effectiveness, good extraction efficiency, shorter analysis run time, low organic solvent consumption, and simpler procedure over the previously reported solid-phase extraction method. The application of this method in pharmacokinetic studies was further demonstrated successfully through a bioequivalence study conducted on healthy human subjects, following oral administration of combined formulation of Olmesartan medoxomil and hydrochlorothiazide in fixed-dose tablet.

A simple, rapid and fully validated HPLC method for simultaneous quantitative bio-analysis of rosuvastatin and candesartan in rat plasma: Application to pharmacokinetic interaction study

A simple, precise and accurate HPLC method was developed, optimized and validated for simultaneous determination of rosuvastatin and candesartan in rat plasma using atorvastatin as an internal standard. Solid-phase extraction was used for sample cleanup and its subsequent optimization was carried out to achieve higher extraction efficiency and to eliminate matrix effect. A quality by design approach was used, wherein three-level factorial design was applied for optimization of mobile phase composition and for assessing the effect of pH of the mobile phase using Design Expert Software. Adequate separation for both analytes was achieved with a Waters C₁₈ column (250 × 4.6 mm, 5 μm) using acetonitrile-5 mm sodium acetate buffer (70:30, v/v; pH adjusted to 3.5 with acetic acid) as a mobile phase at a flow rate of 1.0 mL/min and wavelength of 254 nm. The calibration curves were linear over the concentration ranges 5-150 and 10-300 ng/mL for rosuvastatin (ROS) and candesartan (CAN), respectively. The validated method was successfully applied to a pharmacokinetic study in Wistar rats and the data did not reveal any evidence for a potential drug-drug interaction between ROS and CAN. This information provides evidence for clinical rational use of ROS and CAN.

The simultaneous UPLC-MS/MS determination of emerging drug combination; candesartan and chlorthalidone in human plasma and its application

A novel, precise, sensitive and accurate ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method has been developed for the simultaneous determination of a novel drug combination, candesartan (CAN) and chlorthalidone (CHL), in human plasma. Chromatographic separation was achieved on Waters Acquity UPLC BEH C₁₈ (50 × 2.1 mm, 1.7 μm). Mobile phase consisting of 1 mm ammonium acetate in water-acetonitrile (20:80 v/v) was used. The total chromatographic runtime was 1.9 min with retention times for CAN and CHL at 0.7 and 1.1 min respectively. Ionization and detection of analytes and internal standards was performed on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring and negative ionization mode. Quantitation was done to monitor protonated precursor → product ion transition of m/z 439.2 → 309.0 for CAN, 337.0 → 189.8 for CHL and 443.2 → 312.1 for candesartan D4 and 341.0 → 189.8 for chlorthalidone D4. The method was validated over a wide dynamic concentration range of 2.0-540.0 ng/mL for candesartan and 1.0-180.0 ng/mL for chlorthalidone. The validated method was successfully applied for the assay of CAN and CHL in healthy volunteers.

Mean centering of ratio spectra and concentration augmented classical least squares in a comparative approach for quantitation of spectrally overlapped bands of antihypertensives in formulations

Two different methods manipulating spectrophotometric data have been developed, validated and compared. One is capable of removing the signal of any interfering components at the selected wavelength of the component of interest (univariate). The other includes more variables and extracts maximum information to determine the component of interest in the presence of other components (multivariate). The applied methods are smart, simple, accurate, sensitive, precise and capable of determination of spectrally overlapped antihypertensives; hydrochlorothiazide (HCT), irbesartan (IRB) and candesartan (CAN). Mean centering of ratio spectra (MCR) and concentration residual augmented classical least-squares method (CRACLS) were developed and their efficiency was compared. CRACLS is a simple method that is capable of extracting the pure spectral profiles of each component in a mixture. Correlation was calculated between the estimated and pure spectra and was found to be 0.9998, 0.9987 and 0.9992 for HCT, IRB and CAN, respectively. The methods were successfully determined the three components in bulk powder, laboratory-prepared mixtures, and combined dosage forms. The results obtained were compared statistically with each other and to those of the official methods.

Simultaneous Determination and Pharmacokinetic Study of Losartan, Losartan Carboxylic Acid, Ramipril, Ramiprilat, and Hydrochlorothiazide in Rat Plasma by a Liquid Chromatography/Tandem Mass Spectrometry Method

The monitoring of the plasmatic concentrations of cardiovascular drugs is crucial for understanding their pharmacokinetics and pharmacodynamics. A simple, sensitive, specific, and high-throughput liquid chromatography/tandem mass spectrometry (LC–MS/MS) method was developed and validated for the simultaneous estimation and pharmacokinetic study of losartan (LOS), losartan carboxylic acid (LCA), ramipril (RAM), ramiprilate (RPT), and hydrochlorothiazide (HCZ) in rat plasma using irbesartan (IBS) and metolazone (MET) as internal standards (ISs). After solid phase extraction (SPE), analytes and ISs were separated on an Agilent Poroshell 120, EC-C18 (50 mm × 4.6 mm, i.d., 2.7 μm) column with a mobile phase consisting of methanol/water (85:15, v/v) containing 5 mmol/L ammonium formate and 0.1% formic acid at a flow rate of 0.4 mL/min. The precursor → product ion transitions for the analytes and ISs were monitored on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring (MRM) mode and switching the electrospray ionization (ESI) mode during chromatography from positive (to detect LOS, LCA, RAM, RPT, and IBS) to negative (to detect HCZ and MET). The method was validated as per the FDA guidelines and it exhibited sufficient specificity, accuracy, and precision. The method was found to be linear in the range of 3–3000 ng/mL for LOS and LCA, 0.1–200 ng/mL for RAM and RPT, and 1–1500 ng/mL for HCZ. The described method was successfully applied to the preclinical pharmacokinetic study of analytes after oral administration of a mixture of LOS (10 mg/kg), RAM (1 mg/kg), and HCZ (2.5 mg/kg) in rats.

Improved simultaneous quantitation of candesartan and hydrochlorthiazide in human plasma by UPLC-MS/MS and its application in bioequivalence studies

A validated ultra-performance liquid chromatography mass spectrometric method (UPLC–MS/MS) was used for the simultaneous quantitation of candesartan (CN) and hydrochlorothiazide (HCT) in human plasma. The analysis was performed on UPLC–MS/MS system using turbo ion spray interface. Negative ions were measured in multiple reaction monitoring (MRM) mode. The analytes were extracted using a liquid–liquid extraction (LLE) method by using 0.1 mL of plasma volume. The lower limit of quantitation for CN and HCT was 1.00 ng/mL whereas the upper limit of quantitation was 499.15 ng/mL and 601.61 ng/mL for CN and HCT respectively. CN d₄ and HCT-¹³Cd₂ were used as the internal standards for CN and HCT respectively. The chromatography was achieved within 2.0 min run time using a C18 Phenomenex, Gemini NX (100 mm×4.6 mm, 5 µm) column with organic mixture:buffer solution (80:20, v/v) at a flow rate of 0.800 mL/min. The method has been successfully applied to establish the bioequivalence of candesartan cilexetil (CNC) and HCT immediate release tablets with reference product in human subjects.