Pharmaceutically active compounds (PhACs) in surface water: Occurrence, trends and risk assessment in the Tagus River Basin (Spain).

In this study, the presence of 23 pharmaceutically active compounds (PhACs) including antibiotics, analgesics, anti-inflammatories, psychiatric and cardiovascular drugs, antifungals and metabolites was investigated in surface waters. A total of 89 samples were collected during 3 years (2020, 2021 and 2022) from a European representative river basin (Tagus, Spain). To elucidate PhAC potential sources, sampling points located in areas with low, median and high anthropogenic influence were selected. The analytical method based on solid phase extraction (SPE) followed by UHPLC-MS/MS analysis was validated meeting SANTE/2020/12830 and SANTE/12682/2019 performance criteria. PhACs were quantified above limits of quantification (LOQs) in 96 % of water samples, being the antihypertensives valsartan (648 ng/L, 87 % quantification frequency) and irbesartan (390 ng/L, 75 %) and the antidepressant o-desmethylvenlafaxine (495 ng/L, 76 %) the predominant pollutants. The rest of the target PhACs showed median concentrations between 4 and 172 ng/L with quantification frequencies ranging from 35 to 75 %. ∑PhAC concentrations did not show temporal or seasonal trends. However, valsartan and naproxen presented lower levels in drier (spring and summer) compared to the wetter. Source identification revealed a clear anthropogenic origin since concentrations obtained in highly populated areas were statistically higher (p < 0.01) than those quantified in sparsely populated ones. This finding was also confirmed by calculating PhACs mass flow rates, which ranged between 1.4 and 235 kg/y. Finally, data generated were used to estimate the potential risk to the aquatic ecosystem for three trophic levels (phototrophic, invertebrate and vertebrate organisms). Risk quotient ratios (RQs) were calculated for all PhACs at the median (P50) and worst-case (max) scenarios. Up to 7 PhACs (acetaminophen, carbamazepine, gemfibrozil, ibuprofen, irbesartan, ketoprofen and venlafaxine) showed high risk for the highest trophic level (fish) in >45 % of investigated locations.

A Novel, Sustainable, and Eco-Friendly Spectrophotometric and Chemometric Approach for Determination of Severely Overlapped Spectrum via Unified Regression Equation: Greenness and Whiteness Assessment.

BACKGROUND: Nebivolol and valsartan (VAL) in combination with each other successfully control blood pressure and improve hypertension patient outcomes. OBJECTIVE: To develop and validate innovative, simple, and sustainable spectrophotometric methods for the simultaneous analysis of nebivolol and valsartan. METHOD: The new modified difference amplitude modulation (MD-AM) method uses only unified regression equation and does not require any resolution techniques. Other different approaches were also applied for the determination of the same mixture including univariate and multivariate spectrophotometric methods. The multivariate methods were PLS and PCR, whereas the univariate methods were derivative ratio (DD1), ratio difference (RD), constant center (CC), constant center spectrum subtraction (CC-SS), constant value coupled with amplitude difference (CV-AD), advanced concentration value (ACV), and amplitude difference (AD). The proposed methods use a green solvent; thus, the environmental impact of the presented procedures was evaluated qualitatively and quantitatively using six well-known evaluation tools. RESULTS: All methods were applied successfully for the analysis of the studied drugs in their bulk powder, pharmaceutical dosage form Byvalson®, and in vitro release at intestinal pH (7.4) using a USP dissolution tester. Results obtained were compared statistically with the reported method and with each other using a one-way ANOVA statistical test, and no significant differences were found. CONCLUSIONS: All green and white analytical chemistry evaluation tools results confirm the safety, sustainability, and cost-effectiveness of the approaches, indicating that the methods are regarded green and sustainable. Results were agreeable, encouraging their applicability in quality control laboratories for dosage form and making these methods an eco-friendly substitute for the analysis of this combined dosage form and for evaluating the dissolution profile. HIGHLIGHTS: For the first time, a severely overlapped spectrum was determined using a unified regression equation without the need of extended part or zero contribution regions by the novel method MD-AM. The proposed methods are the first study of in vitro dissolution profiling of nebivolol hydrochloride (NEB) and VAL and the first sustainable and green methods applied without compromising the analytical criteria.

Investigation of Carcinogenic Impurities of N-Nitrosamines in Sartan Pharmaceutical Products Marketed in Brazil: Development and Validation of Method Based on High-Performance Liquid Chromatography-Tandem Mass Spectrometry.

N-nitrosamines (NA) impurities have unexpectedly been found in sartan products, angiotensin II receptor antagonists that are used to control hypertension, representing an urgent concern for industry, global regulators and for the patients. In this study, an HPLC-MS/MS method was developed and validated for the quantification of six NA (N-nitrosodimethylamine, N-Nitroso-N-methyl-4-aminobutyric acid, N-Nitrosodiethylamine, N-ethyl-N-nitroso-2-propanamine, N-nitroso-diisopropylamine and N-nitroso-di-n-butylamine) in losartan, valsartan, olmesartan, irbesartan, candesartan and telmisartan products. The method was validated in terms of sensitivity, linearity, accuracy, precision, robustness and stability. The limits of quantification were 100, 31.25, 250, 33, 312.5 and 125 µg kg-1 in losartan, valsartan, olmesartan, irbesartan, candesartan and telmisartan samples, respectively, which met the sensitivity requirements for the limits set by Food and Drug Administration of the United States. The standard curves showed good linearity. The recoveries ranged from 93.06 to 102.23% in losartan matrix, 83 to 85.9% in valsartan, 96.1 to 101.2% in olmesartan, 89.2 to 97.5% in irbesartan, 93.4 to 132.0% in candesartan and 62.3 to 106.2% in telmisartan matrix. The other parameters met the validation criteria, the good sensitivity and precision, high accuracy and simple and fast analysis provides a reliable method for quality control of NA in sartan pharmaceutical products. The developed method was successfully applied for the determination of N-nitrosamines in 71 sartan products marketed in Brazil.

Sartan blood pressure regulators in classical and biofilm wastewater treatment - Concentrations and metabolism.

Sartans are a group of pharmaceuticals widely used to regulate blood pressure. Their concentration levels were monitored in 80 wastewater treatment plants (WWTP) in the Baltic Sea Region, reached from limit of detection up to 6 µg/L. The concentrations were significantly different in different countries, but consistent within the respective country. The degradation of sartans (losartan, valsartan, irbesartan) in moving bed biofilm reactors (MBBRs) that utilize biofilms grown on mobile carriers to treat wastewater was investigated for the first time, and compared with the degradation in a conventional activated sludge (CAS) treatment plant. The results showed the formation of six microbial transformation products (TPs) of losartan, four of valsartan, and four of irbesartan in biological wastewater treatment. Four of these metabolites have not been described in the literature before. Chemical structures were suggested and selected TPs were verified and quantified depending on availability of true standards. Valsartan acid was a common TP of losartan, valsartan, and irbesartan. Losartan and irbesartan also shared one TP: losartan/irbesartan TP335. Based on the mass balance analysis, losartan carboxylic acid is the main TP of losartan, and valsartan acid is the main TP of valsartan during the biotransformation process. For irbesartan, TP447 is likely to be the main TP, as its peak areas were two orders of magnitude higher than those of all the other detected TPs of this compound. The effects of adapting biofilms to different biological oxygen demand (BOD) loading on the degradation of sartans as well as the formation of their TPs were investigated. Compared to feeding a poor substrate (pure effluent wastewater from a CAS), feeding with richer substrate (1/3 raw and 2/3 effluent wastewater) promoted the metabolism of most compounds (co-metabolization). However, the addition of raw wastewater inhibited some metabolic pathways of other compounds, such as from losartan/irbesartan to TP335 (competitive inhibition). The formation of irbesartan TP447 did not change with or without raw wastewater. Finally, the sartans and their TPs were investigated in a full-scale CAS wastewater treatment plant (WWTP). The removal of losartan, valsartan, and irbesartan ranged from 3.0 % to 72% and some of the transformation products (TPs) from human metabolism were also removed in the WWTP. However, some of the sartan TPs, i.e., valsartan acid, losartan carboxylic acid, irbesartan TP443 and losartan TP453, were formed in the WWTP. Relative high amounts of especially losartan carboxylic acid, which was detected with concentrations up to 2.27 µg/L were found in the effluent.

Biochar from palm fiber wastes as an activator of different oxidants for the elimination of pharmaceuticals from diverse classes in aqueous samples.

Biochar (BP) obtained from palm fiber wastes was combined with H2O2, peroxymonosulfate (PMS), or persulfate (PDS) to treat valsartan, acetaminophen, and cephalexin in water. BP activated PMS and PDS but no H2O2. Computational calculations indicated that interactions of PMS and PDS with BP are more favored than those with HP. The highest synergistic effect was obtained for the removal of valsartan by BP + PMS. This carbocatalytic process was optimized, evaluating the effects of pH, BP dose, and peroxymonosulfate concentration, and minimizing the oxidant quantity to decrease costs and environmental impacts of the process. SO4•-, HO•, 1O2, and O2•- were the agents involved in the degradation of the pharmaceuticals. The reusability of BP was tested, showing that the carbocatalytic process removed ∼80% of target pollutants after 120 min of treatment even at the fourth reuse cycle. Also, the process decreased the phytotoxicity of the treated sample. Simulated hospital wastewater was treated and its components induced competing effects, but the system achieved the target pharmaceuticals removal in this matrix. Additionally, the analysis of environmental impact using a life cycle assessment unraveled that the carbocatalytic process had a carbon footprint of 2.87 Kg CO2-Eq, with the biochar preparation (which involves the use of ZnCl2 and electric energy consumption) as the main hotspot in the process.

Enzymatic activity on valsartan of 38 CYP2C9 variants from the Chinese population.

BACKGROUND AND OBJECTIVE: Valsartan is widely used for the treatment of moderate hypertension. However, previous studies have found that efficacy of the valsartan depends on the dose and intake. Cytochrome P450 (CYP) 2C9 metabolizes ∼15% of the clinical drugs. Genetic polymorphisms of CYP2C9 markedly affect the safety and effectiveness of many drugs, which might lead to adverse reactions and therapeutic failure. Twenty-four novel CYP2C9 variants (*36-*60) had been previously discovered via gene sequencing in the Han population. Our study aims to evaluate the impact of 38 CYP2C9 variants from the Chinese population on valsartan metabolism compared with CYP2C9*1 in vitro. METHODS: Wild-type CYP2C9*1 and other CYP2C9 variants were expressed in Spodoptera frugiperda 21 insect cells. Incubations were performed at 37 °C with 20-2000 µM substrate for 30 min. The metabolite 4-OH valsartan was determined via UPLC-MS/MS. RESULTS: Among the 38 CYP2C9 variants, the enzymatic activities of most variants were significantly altered compared with the wild-type. Three variants (CYP2C9*27, *40 and *49) exhibited increased intrinsic clearance values (134-153% relative clearance). However, 12 variants (CYP *8, *13, *16, *19, *33, *36, *42, *43, *45, *52, *54, *58) caused >90% decreases in the relative clearance of valsartan compared to CYP2C9*1. CONCLUSIONS: Our research provides systematic data for evaluating the effects of CYP2C9 variants on valsartan metabolism in the Chinese population. These results will expand our understanding of the impact of CYP2C9 genetic polymorphisms on valsartan metabolism and will contribute to precision medicine.

Stability-indicating reversed-phase-HPLC method development and validation for sacubitril/valsartan complex in the presence of impurities and degradation products: Robustness by quality-by-design approach.

According to current regulatory guidelines, a stability-indicating method has been developed to determine the impurities in sacubitril (SCB) and valsartan (VLS) tablet dosage forms and perform robustness studies using the design of experiments approach. The present study was initiated to understand quality target product profile, analytical target profile, and risk assessment for method variables that affect the method response. A reversed-phase-HPLC system was equipped with a Phenomenex Gemini-NX C18 column (150 × 4.6 mm, 3 µm) and a photo diode array detector. A gradient mobile phase was used in this research work. The detection was performed at 254 nm; the flow rate was 1.5 mL/min, and the column temperature was maintained at 30°C. The proposed method was validated per the International Council for Harmonisation Q2 (R1) guidelines. The coefficient of correlation was >0.999 for all impurities. The limits of detection and quantification were evaluated for SCB, VLS, and all impurities. The precision and accuracy were obtained for SCB, VLS, and their related impurities. Intra- and inter-day relative standard deviation values were less than 10.0%, and the recoveries of impurities varied between 90.0 and 115.0%. Based on the validation results, the proposed DoE method can estimate SCB and VLS impurities in the finished dosage form.

New liquid chromatography assays for simultaneous quantification of antihypertensives atenolol and valsartan in their dosage forms.

Nowadays, various single-pill combinations are used as the best choice in hypertension management. However, these pills made a high challenge to analysts in terms of quality control assays. We have developed three sensitive, selective, fast, simple, green, accurate, precise, and robust isocratic high-performance liquid chromatography methods for simultaneous determination of valsartan and atenolol in dosage forms. To find the appropriate high-performance liquid chromatography conditions for the separation of the examined drugs, various columns, isocratic mobile phase systems were tried, and successful attempts were performed. The used columns proved to be indispensably applicable and gave a shorter analysis time and peak symmetries. This reduction in total run time leads to low solvent consumption and makes all methods more economical. The linearity, accuracy, and precision remained within the acceptable limits. Therefore, all developed methods are suitable for the routine quality control analysis of any pharmaceutical preparation containing the two tested drugs with the proposed chromatographic methods advantages for checking quality during stability studies of their pharmaceutical preparations.

High performance liquid chromatographic assay of amlodipine, valsartan and hydrochlorothiazide simultaneously and its application to pharmaceuticals, urine and plasma analysis.

A Simple, Specific, Precise, Accurate, Linear, Rugged, Robust High Performance Liquid Chromatographic method of analysis for simultaneous determination of assay of Amlodipine, Valsartan and Hydrochlorothiazide drugs in the pharmaceuticals tablet formulations using Pioglitazone as a common internal standard was developed and validated. The assay was accomplished using a mixture of acetonitrile & methanol in the volume ratio of 20:80 v/v (mobile phase B) and Ammonium acetate buffer (Mobile phase A) in gradient flow as mobile phase on an Hibar RP-18e, 250 × 4.6 mm, 5µ as chromatographic column at a flow rate of 1.300 mLmin-1, injection volume 10 µL and at a wavelength 235 nm with UV detector. Linearity of the analytical method was evaluated at a concentration range of 2.5-45.3 µg/ml for Amlodipine, 32.0-720.1 µg/ml for valsartan and 5.0-112.6 µg/ml for Hydrochlorothiazide respectively with Correlation coefficient (r) value more than 0.9997. The limit of detection (LOD) for Amlodipine, Valsartan and Hydrochlorothiazide was found to be 1.1 µg/ml, 8.0 µg/ml & 1.0 µg/ml respectively. Specificity, Method Precision, System Precision, Ruggedness, Robustness, Recovery, Stability of analytical solution, Filter paper selection study, Stress testing (Force Degradation) at various conditions were performed as per the ICH (Q2) recommendations. The chromatographic method may also be applied for simultaneous estimation of analytes in plasma and urine.

Simultaneous determination of Nebivolol hydrochloride and Valsartan in their binary mixture using different validated spectrophotometric methods.

Five simple, sensitive, accurate and precise spectrophotometric methods were developed for the simultaneous determination of Nebivolol hydrochloride (NEB) and Valsartan (VAL) in their binary mixtures and in pharmaceutical dosage form. The methods included Ratio Difference, First Derivative ratio, Mean Centering of ratio spectra, Bivariate and H-Point Standard additions method. The calibration curves were linear over the concentration range of 10-70 µg/ml and 20-60 µg/ml for NEB and VAL, respectively for Ratio Difference and First Derivative ratio method and over the concentration range of 10-70 µg/ml and 10-60 µg/ml for NEB and VAL, respectively for Mean Centering of ratio spectra, Bivariate and H-Point Standard additions method. These methods were examined by analyzing synthetic mixtures of the studied drugs and they were utilized to determine the studied drugs in their commercial pharmaceutical preparation. All methods were validated as per ICH guidelines and accuracy, robustness, repeatability and precision were found to be within the acceptable limits. The results of the proposed methods were compared to the results of reported methods with no significant difference between them.

HPLC method transfer study for simultaneous determination of seven angiotensin II receptor blockers.

In this study, a sensitive high-performance liquid chromatography method was developed and validated for the simultaneous determination of seven angiotensin II receptor blockers, namely, hydrochlorothiazide, chlorthalidone, eprosartan mesylate, valsartan, losartan potassium, irbesartan, and candesartan cilexetil. Different chromatographic parameters were tested and fully optimized. Best chromatographic separation was accomplished on a reversed-phase octadecylsilyl column (250 × 4.6 mm id; 5 µm) under gradient elution using methanol/sodium phosphate monobasic buffer (0.01 M, pH 6.5) as mobile phase. The detection of target analytes was obtained at 254 nm. The pH of the buffer has been selected according to Marvin® sketch software. The proposed method was validated according to ICH guidelines and showed good precision (relative standard deviation < 1), good linearity (square of correlation coefficient ≥ 0.999), and high accuracy (between 98 and 102%) with detection limit and quantitation limit (40 and 160 ng/mL, respectively) for all the detected analytes.

Rapid and efficient high-performance liquid chromatography analysis of N-nitrosodimethylamine impurity in valsartan drug substance and its products.

In July 2018, certain valsartan-containing drugs were voluntary recalled in Japan owing to contamination with N-nitrosodimethylamine (NDMA), a probable human carcinogen. In this study, an HPLC method was developed for the quantitative detection of NDMA simultaneously eluted with valsartan. Good linearity with a correlation coefficient (R2) > 0.999 was achieved over the concentration range of 0.011-7.4 µg/mL. The limits of detection and quantification were 0.0085 µg/mL and 0.0285 µg/mL, respectively. When the recalled valsartan samples were subjected to this method, the observed NDMA contents were in agreement with the reported values, indicating that our method achieved sufficient linearity, accuracy, and precision to detect NDMA in valsartan drug substances and products. Moreover, six samples (valsartan drug substances and tablet formulations), which had a possibility for NDMA contamination, were analyzed; none of the samples contained NDMA at detectable levels. Our method would be useful for the rapid screening and quantification of NDMA impurity in valsartan drug substances and products.

Simultaneous detection of nitrosamines and other sartan-related impurities in active pharmaceutical ingredients by supercritical fluid chromatography.

Since July 2018, the pharmacological class of "sartans" has been the subject of considerable media and analytical interest, as it became known that they are contaminated with nitrosamines such as N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA) and N-nitrosodiisopropylamine (NDiPA). Previous compendial methods are not able to detect these new contaminants. Using the latest and innovative Quality-by-Design (QbD) approach, it has now been possible to develop an analytical method that enables to investigate sartans, such as valsartan and losartan. Also a large class of different nitrosamines in the ppb range and sartan-related impurities can thus be determined simultaneously in a single analysis using supercritical fluid chromatography (SFC). By using SFC, a broad spectrum of nonpolar and very polar impurities can be separated and analyzed in under 20 min. The analytical method developed is validated for limit testing according to ICH Q2(R1) and fulfills default thresholds of EMA and FDA for testing of drug substances and genotoxic impurities. Additionally, it can also be adapted to other pharmaceuticals that may be contaminated with nitrosamines, since tetrazole synthesis as the underlying cause of nitrosamine contamination is important for a set of other non-sartan drug substances.

Selective determination of sartan drugs in environmental water samples by mixed-mode solid-phase extraction and liquid chromatography tandem mass spectrometry.

Herein, a method for the simultaneous determination of the currently prescribed sartan drugs (eprosartan, EPR; olmesartan, OLM; losartan, LOS; candesartan, CAN; telmisartan, TEL; irbesartan, IRB; and valsartan, VAL), and the biodegradation product valsartan acid (VALA), in water samples (raw and treated wastewater, river and tap water) was developed. Solid-phase extraction (SPE) and ultra-performance liquid chromatography (UPLC) tandem mass spectrometry (MS/MS) were employed as concentration and determination techniques, respectively. Different sorbents and elution solvents were tested for sample preparation. Under optimized conditions, samples at neutral pH (6-8 units) were concentrated using mixed-mode (reversed-phase and anionic exchange) cartridges. Thereafter, the sorbent was washed with 5 mL of a methanol: water (1:1) solution, dried under a nitrogen stream and compounds were eluted with 2 mL of methanol: NH3 (98:2). The accuracy of the method (accounting for SPE efficiency and matrix effects during electrospray ionization) was investigated using solvent-based calibration standards. Global recoveries, obtained for different water matrices (tap, river, treated and raw wastewater), ranged from 82% to 134%, with standard deviations between 2 and 18%. LOQs varied from 2 to 50 ng L-1. Analysis of un-spiked samples confirmed: (1) the incomplete removal of sartans at sewage treatment plants (STPs), (2) the formation of VALA during municipal water treatment, and (3) the presence of VALA in the processed tap water samples. Additional findings of the current study are the detection of hydroxylated derivatives of the sartan drugs IRB and LOS in wastewater, and the E-Z isomerization of EPR in environmental water samples.

Analysis of an Impurity, N-Nitrosodimethylamine, in Valsartan Drug Substances and Associated Products Using GC-MS.

Valsartan products, commonly used to treat high blood pressure and heart failure, have been recalled in many countries due to the presence of an impurity, N-nitrosodimethylamine (NDMA), in the recalled products. We present and evaluate a GC-MS-based analytical method for the determination of NDMA levels and attempt an investigation of NDMA concentrations in valsartan drug substances and associated products. The limit of detection and limit of quantification for the method were estimated to be 0.1 and 0.5 µg/g, respectively, when testing a 0.5-g sample. A good trueness (99%) with a small relative standard deviation (1.9%) was obtained for a valsartan product spiked with NDMA at a concentration of 1.0 µg/g. Additionally, a valsartan drug substance and the associated product, which were previously determined to have NDMA contamination, were analyzed by the method. The NDMA content by our method was very close to previously determined values. Finally, six samples, including valsartan drug substances and associated, commercially available products in Japan, all of which were derived from the company implicated in the NDMA contamination, were analyzed by our method, revealing that none of these samples contained detectable concentrations of NDMA. Overall, the data indicate that the present method is reliable and useful for determination of NDMA in valsartan drug substances and associated products.

NDMA impurity in valsartan and other pharmaceutical products: Analytical methods for the determination of N-nitrosamines.

Batch recalls for valsartan containing pharmaceutical products in July 2018 initiated a discussion on possible contaminations with N-nitrosodimethylamine (NDMA). It appeared that NDMA was generated during synthesis of the active pharmaceutical ingredient (API) from the solvent dimethylformamide (DMF) and the reagent nitrite. Discussion on NDMA as API impurity is extended to other drugs since then. Already several years before scientific literature reported NDMA as impurity of several other drugs, thus underlining the apparent risk. At present none of the pharmacopoeias tests for NDMA and only very limited publications of methods for its determination in pharmaceuticals are published so far. This review summarizes aspects for the analyses of nitrosamines (NAs) with special focus on NDMA and discusses their potential applicability for drug analyses. The majority of recent publications utilize GC-MS or GC-MS/MS due to its high selectivity and low detection levels. GC-TEA also provides high selectivity for nitrosamines. However, current availability of this combination is very limited. Alternatively, LC-MS/MS is also performed in NA analysis. An integration of a general test in future pharmacopoeias is suggested due to the toxicological relevance and broader spectrum of possible APIs that may be affected.

Saliva versus Plasma Bioequivalence of Valsartan/Hydrochlorothiazide in Humans: Validation of Classes II and IV Drugs of the Salivary Excretion Classification System.

AIM: The aim of this study is to investigate the robustness of using non-invasive saliva instead of plasma for bioequivalence of valsartan and hydrochlorothiazide (HCT) in humans based on Salivary Excretion Classification System (SECS). METHODS: Plasma and resting saliva samples were collected over 24 h after oral administration of single dose 160 mg valsartan and 12.5 mg HCT to 12 healthy male volunteers after 10 h overnight fasting. Plasma and saliva concentrations were determined by validated liquid chromatography-mass spectrometry. WinNonlin program V5.2 was used to determine pharmacokinetic parameters and bioequivalence metrics. Moreover, optimized effective intestinal permeability was estimated using PK-Sim/Mobi program V5.6. RESULTS AND DISCUSSION: Valsartan is SECS class IV drug due of low permeability and high protein binding and hence didn't appear in saliva. However, HCT is SECS class II drug due to low permeability and low protein binding. No significant differences were observed in the pharmacokinetic parameters in both plasma matrix and saliva matrix (P˃0.05). The 90% confidence intervals did not pass in all parameters due to the high intra-subject variability and small sample size used in this study. Saliva to plasma ratios of HCT were low, yet with high correlation coefficient of 0.96-0.98. So saliva can be used as alternative to plasma sample in pharmacokinetic studies and in bioequivalence when adequate sample size is used.

Innovative spectrophotometric methods for simultaneous estimation of the novel two-drug combination: Sacubitril/Valsartan through two manipulation approaches and a comparative statistical study.

Different innovative spectrophotometric methods were introduced for the first time for simultaneous quantification of sacubitril/valsartan in their binary mixture and in their combined dosage form without prior separation through two manipulation approaches. These approaches were developed and based either on two wavelength selection in zero-order absorption spectra namely; dual wavelength method (DWL) at 226nm and 275nm for valsartan, induced dual wavelength method (IDW) at 226nm and 254nm for sacubitril and advanced absorbance subtraction (AAS) based on their iso-absorptive point at 246nm (λiso) and 261nm (sacubitril shows equal absorbance values at the two selected wavelengths) or on ratio spectra using their normalized spectra namely; ratio difference spectrophotometric method (RD) at 225nm and 264nm for both of them in their ratio spectra, first derivative of ratio spectra (DR1) at 232nm for valsartan and 239nm for sacubitril and mean centering of ratio spectra (MCR) at 260nm for both of them. Both sacubitril and valsartan showed linearity upon application of these methods in the range of 2.5-25.0µg/mL. The developed spectrophotmetric methods were successfully applied to the analysis of their combined tablet dosage form ENTRESTO™. The adopted spectrophotometric methods were also validated according to ICH guidelines. The results obtained from the proposed methods were statistically compared to a reported HPLC method using Student t-test, F-test and a comparative study was also developed with one-way ANOVA, showing no statistical difference in accordance to precision and accuracy.

Structural description of the marketed form of valsartan: A crystalline mesophase characterized by nanocrystals and conformational disorder.

Valsartan is an antihypertensive drug, recognized to be marketed in an amorphous state, different from that obtained by quenching the liquid state below Tg. This is an unusual and very original situation, given that the amorphous state is unstable. Low-wavenumber Raman spectroscopy and X-ray diffraction investigations were carried out on the various solid-state forms of valsartan. It was found that the marketed form is not amorphous and can be described in terms of mesophase in which the long-range order of the stable crystal is limited on the lengthscale of tens nanometers, inducing a melting temperature lower than that of the stable crystalline state, inherent to the crystallite size. This unusual physical state of a marketed drug was correlated to the relative population of cis-trans conformers, preventing the development of the hydrogen-bond network distinctive of the long-range order in the crystalline state.

Multiway analysis methods applied to the fluorescence excitation-emission dataset for the simultaneous quantification of valsartan and amlodipine in tablets.

In this study, excitation-emission matrix datasets, which have strong overlapping bands, were processed by using four different chemometric calibration algorithms consisting of parallel factor analysis, Tucker3, three-way partial least squares and unfolded partial least squares for the simultaneous quantitative estimation of valsartan and amlodipine besylate in tablets. In analyses, preliminary separation step was not used before the application of parallel factor analysis Tucker3, three-way partial least squares and unfolded partial least squares approaches for the analysis of the related drug substances in samples. Three-way excitation-emission matrix data array was obtained by concatenating excitation-emission matrices of the calibration set, validation set, and commercial tablet samples. The excitation-emission matrix data array was used to get parallel factor analysis, Tucker3, three-way partial least squares and unfolded partial least squares calibrations and to predict the amounts of valsartan and amlodipine besylate in samples. For all the methods, calibration and prediction of valsartan and amlodipine besylate were performed in the working concentration ranges of 0.25-4.50µg/mL. The validity and the performance of all the proposed methods were checked by using the validation parameters. From the analysis results, it was concluded that the described two-way and three-way algorithmic methods were very useful for the simultaneous quantitative resolution and routine analysis of the related drug substances in marketed samples.