Synchronized determination of sacubitril and valsartan with some co-administered drugs in human plasma via UPLC-MS/MS method using solid-phase extraction.

An accurate and sensitive UPLC-MS/MS method was developed and validated for the simultaneous estimation of the newly developed combination of sacubitril and valsartan and the co-administered drugs nebivolol, chlorthalidone and esomeprazole in human plasma. Solid-phase extraction was conducted for the purification and extraction of the drugs from human plasma. Chromatographic separation was carried out on an Agilent SB-C18 (1.8 µm, 2.1 × 50 mm) column using losartan as internal standard. Isocratic elution was applied using acetonitrile-0.1% formic acid in water (85: 15, v/v) as mobile phase. Detection was carried out using a triple-quadrupole tandem mass spectrometer using multiple reaction monitoring, at positive mode at m/z 412.23 → 266.19 for sacubitril, m/z 436.29 → 235.19 for valsartan, m/z 405.8 → 150.98 for nebivolol, m/z 346.09 → 198 for esomeprazole and a selected combination of two fragments m/z 423.19 → 207.14 and 423.19 → 192.2 for losartan (internal standard), and in negative ionization mode at m/z 337.02 → 190.12 for chlorthalidone. The method was linear over the concentration ranges 30-2,000 ng/ml for sacubitril, 70-2,000 ng/ml for valsartan, esomeprazole and chlorthalidone and 70-5,000 pg/ml for nebivolol. The developed method is sensitive and selective and could be applied for dose adjustment, bioavailability and drug-drug interaction studies.

Application of experimental design in HPLC method optimization and robustness for the simultaneous determination of canagliflozin, empagliflozin, linagliptin, and metformin in tablet.

Gliflozins and gliptins represent two different pharmacological drug classes that exert different and potentially complementary glucose-lowering effect in patients with type II diabetes mellitus. A novel, selective, and sensitive HPLC method was developed for the determination of canagliflozin, empaglifozin, linagliptin, and metformin in pure form, in laboratory prepared mixtures, and in pharmaceutical dosage form. Experimental design optimization was applied by using Plackett-Burman and face-centered composite designs to achieve the best resolution with minimum experimental trials. Three significant variables affecting optimization, namely buffer pH, percentage of methanol, and percentage of acetonitrile, were studied. Chromatographic separation was achieved using an Agilent Eclipse C8 column, and column temperature was kept at 45°C. The mobile phase was composed of dipotassium hydrogen phosphate buffer (0.05 M, adjusted to pH 6 using o-phosphoric acid):acetonitrile:methanol (50:25:25, v/v/v) at a flow rate of 1.5 mL/min. Sharp and well-resolved peaks of the cited drugs were obtained. The method was fully validated in terms of linearity, accuracy, precision, selectivity and robustness in agreement with the International Council of Harmonization (ICH) guidelines Q2 (R1). Satisfactory results were obtained by the analysis of tablets through applying the developed method. Therefore, it could be performed for the analysis of the cited drugs in quality control laboratories.

Smart spectrophotometric methods for the simultaneous determination of newly co-formulated hypoglycemic drugs in binary mixtures.

Achieving good glycemic control in patients with type II diabetes mellitus is essential for preventing both microvascular and macrovascular complications. Combination therapy represents the principle strategy for successful long term control of type II diabetes mellitus with minimal complications. Two sensitive, precise and non-destructive spectroscopic methods were developed for the simultaneous estimation of two new co-formulated hypoglycemic drugs; canagliflozin/metformin (CAG/MEF) and empagliflozin/linagliptin (EMG/LIG) in tablets with no need of previous separation. The first method was amplitude modulation (a normalized spectra-based UV spectrophotometric method) for the analysis of (CAG/MEF) binary mixture. The amplitude of the constant at the plateau region at (264-310 nm) on the ratio spectrum was measured and used for the determination of CAG concentration in the mixture. On the other hand, MEF was estimated by subtracting the previously obtained amplitude from the total amplitude of CAG and MEF at the isosbestic point (λiso) at 250 nm. The second method was chemometric-assisted FTIR spectrophotometric method for the determination of (EMG/LIG) binary mixture. (EMG/LIG) mixture in chloroform was analyzed using FTIR in the region 4000-400 cm-1. The spectral region 3900-2900 cm-1 was selected for (EMG/LIG) determination using principal component regression and partial least squares chemometric methods. The methods were validated according to ICH guidelines. The studied drugs were successfully determined in tablets applying the developed methods. Validation parameters were in agreement with acceptance limits, ensuring methods accuracy and selectivity. Besides, no significant difference was obtained by statistically comparing the obtained results with the reported one.

Simultaneous determination of enalapril maleate and nitrendipine in tablets using spectrophotometric methods manipulating ratio spectra.

A fixed dose combination of enalapril maleate (EN) and nitrendipine (NT) achieved satisfactory blood pressure control rather than monotherapy. Four accurate spectrophotometric methods utilizing ratio spectra were developed and validated for the simultaneous determination of EN and NT in combined pharmaceutical dosage form (Eneas® tablets). The first method was first derivative ratio spectrophotometric method (1DD) where the amplitudes maxima were measured at 219.2 nm and 233.4 nm for the determination of EN and NT, respectively. The second method was ratio difference spectrophotometric method where EN and NT were estimated by measuring the amplitudes difference between 213 nm and 225 nm on the ratio spectrum of EN and between 241 nm and 227 nm on the ratio spectrum of NT. The third method was ratio subtraction followed by extended ratio subtraction, EN was determined at 210 nm by subtraction of the constant values from the ratio spectrum then multiplication with the divisor (NT spectrum). An extended ratio subtraction method was then applied in order to determine NT at 235 nm by using the zero-order spectrum of EN (10 µg/ml) as a divisor. The fourth method was ratio subtraction coupled with constant multiplication methods. The zero- order absorption spectrum of the laboratory prepared mixture was divided by NT (12 µg/ml) spectrum, subsequently, the value of the constant was multiplied by the divisor to obtain the original spectrum of NT, followed by its subtraction from the laboratory prepared mixture to get the spectrum of EN. EN and NT were determined at 210 nm and 235 nm, respectively. Linearity was ascertained over the concentration ranges of (1-11 µg/ml) for EN and (2-14 µg/ml) for NT, for the first and second methods and (2-13 µg/ml) for EN and (3-20 µg/ml) of NT, for the third and fourth methods. Application of the methods to the determination of the cited drugs in Eneas® tablets gave satisfactory results. Methods validation confirmed their accuracy and selectivity. Statistical comparison of the results with the reported one showed no significant difference, regarding precision and accuracy. Routine analysis of the cited drugs in quality control laboratories could be performed using the developed methods.

Simultaneous determination of cefixime and erdosteine in combined dosage form using validated spectrophotometric methods.

Four accurate and precise spectrophotometric methods were developed and validated for the simultaneous determination of a binary mixture of cefixime (CEF) and erdosteine (ERD) without previous separation. Method A was first derivative ratio spectrophotometric method (1DD) where the amplitudes at 310 and 315 nm and the amplitude at 248 nm were chosen to simultaneously estimate CEF and ERD, respectively. Method B depends on ratio difference spectrophotometry (RDSM), in which the difference in amplitudes at 325 and 326 nm on the ratio spectrum of the mixture was directly proportional to the concentration of CEF; independent of the interfering component. Similarly, the amplitude difference between 236 and 249 nm on the ratio spectrum was used for the determination of ERD. Method C was based on simultaneous determination of CEF and ERD using classical least squares (CLS) and partial least squares (PLS) chemometric techniques. Method D was the mean centering of ratio spectra (MCR) at 313 and 237 nm for the determination of CEF and ERD respectively. The developed methods were successfully employed to the determination of CEF and ERD in laboratory prepared mixtures and dosage form showing satisfactory recoveries. Methods validation was performed according to the International Conference on Harmonization (ICH) guidelines. The obtained results were statistically compared to those of the reference method, revealing no significant difference with respect to precision and accuracy. Precision and cost effectiveness of the developed methods permit their application in quality control laboratories for the determination of the binary mixture.

Validated LC-MS/MS method for the simultaneous determination of enalapril maleate, nitrendipine, hydrochlorothiazide, and their major metabolites in human plasma.

Hypertension is a major risk factor for atherosclerosis and ischemic heart disease. Most hypertensive patients need a combination of antihypertensive agents to achieve therapeutic goals. A rapid, sensitive, and selective liquid chromatography-tandem mass spectrometric method was developed and validated for simultaneous determination of enalapril maleate (ENA) and its major metabolite enalaprilat (ENAT), nitrendipine (NIT) and its major metabolite dehydronitrendipine (DNIT), and hydrochlorothiazide (HCT) in human plasma using felodipine as an internal standard (IS). The drugs were extracted from plasma using one-step protein precipitation. Chromatographic separation was performed on a Symmetry C18 column, with water and acetonitrile (10:90, v/v) as mobile phase. The detection was carried out using multiple reaction monitoring mode and coupled with electrospray ionization source. Multiple reaction monitoring transitions were m/z 377.1 → 234.1 for ENA, m/z 349.2 → 206.1 for ENAT, m/z 361.2 → 315.1 for NIT, m/z 359 → 331 for DNIT, m/z 295.9 → 205.1 for HCT, and m/z 384.1 → 338 for felodipine (IS). The method was linear over concentration ranges of 1-200, 20-500, 5-200, 2-100, and 5-200 ng/mL for ENA, ENAT, NIT, DNIT, and HCT, respectively, with r2 ≥ 0.99. Method validation was performed according to U.S. Food and Drug Administration guidelines. The validated method showed good sensitivity and selectivity and could be applied for therapeutic drug monitoring and bioequivalence studies.

A validated RP-HPLC method for the evaluation of the influence of grapefruit juice on liver S9 activation of sacubitril.

Grapefruit juice inhibits esterase enzyme. Therefore, a possible interaction with ester prodrugs should be taken into consideration. In this study, the influence of grapefruit juice on sacubitril (SAC) rat liver S9 activation by esterase enzyme was evaluated. An RP-HPLC method was developed and validated for estimation of SAC in rat liver S9 fraction using a C18 Cyano column as stationary phase and acetonitrile-sodium di-hydrogen phosphate buffer (0.02 m, pH 4 adjusted by o-phosphoric acid, 40:60, v/v), as mobile phase at a flow rate of 1 mL/min and UV detection at 254 nm. The method was successfully applied to an in vitro study in which SAC was incubated with rat liver S9 fraction prepared from rats that had previously ingested grapefruit juice for a week. The calculated SAC concentration after incubation was compared with that of SAC incubated with rat liver S9 fraction from the rat control group. The statistical significance between the results of test and control incubation sets was assessed. In conclusion, the current study demonstrated that grapefruit juice decreased SAC hydrolysis, hence delaying its activation to sacubitrilat (active form) in gut lumen. Based on this food-drug interaction, it may be required that grapefruit juice should be consumed with caution in patients receiving SAC.

A validated LC-MS/MS method for simultaneous determination of linagliptin and metformin in spiked human plasma coupled with solid phase extraction: Application to a pharmacokinetic study in healthy volunteers.

Combination therapy has a pivotal role in type II diabetes mellitus management in patients unable to maintain normal glycemic level using metformin alone. Addition of linagliptin, dipeptidyl peptidase-IV inhibitor, to metformin improves glycemic control. This study is concerned with the development of an HPLC-MS/MS method for simultaneous quantification of linagliptin and metformin in spiked human plasma. The method was applied to evaluate the potential pharmacokinetic interactions between the cited drugs in healthy volunteers. Solid phase extraction was applied using Strata™ X cartridge. Separation was carried out on Symmetry® C18 column using methanol: 10 mM ammonium formate buffer (containing 0.2% formic acid) in a ratio of (95: 5, v/v) as mobile phase at flow rate 0.25 mL min-1. Quantification was performed with multiple reaction monitoring in positive ionization mode. The monitored transitions were set at m/z 473.24 → 419.94, 130.14 → 60.18 and 340.27 → 116.07 for linagliptin, metformin and alogliptin (internal standard), respectively. The method was validated according to FDA guidelines. The method showed excellent linearity over concentration ranges 0.25-10 and 25-2000 ng mL-1 for linagliptin and metformin, respectively. The validated HPLC-MS/MS method was successfully applied to pharmacokinetic study of linagliptin and metformin in healthy volunteers after oral administration of Jentadueto® tablets.

Different resolution techniques for management of overlapped spectra: Application for the determination of novel co-formulated hypoglycemic drugs in their combined pharmaceutical dosage form.

To maintain intensive glucose control early in the type II diabetes mellitus process, novel combinations of canagliflozin/metformin (CAG/MEF) and empagliflozin/linagliptin (EMG/LIG) offer particular treatment benefits. In this study, sensitive and precise spectrophotometric methods were developed for the determination of such hypoglycemic drug combinations in bulk powder and in pharmaceutical dosage form without prior separation. The first method was ratio difference coupled with modified isosbestic point technique where the amplitude difference between 239 and 291 nm on the ratio spectrum of CAG obtained using 4 µg/ml of MEF as divisor was used for determination of CAG. On the other hand, MEF was estimated using a modified isosbestic spectrophotometric method, where the total concentration of CAG and MEF in mixture could be calculated at 250 nm (isosbestic point) after multiplication by a correction factor. Then concentration of MEF could be calculated by subtraction. The second method was ratio subtraction coupled with extended ratio subtraction, where EMG was determined at 225 nm by subtraction of plateau values from the ratio spectrum followed by multiplication with the spectrum of 6.5 µg/ml of LIG (divisor). Then, an extension of the normal ratio subtraction method was performed in order to determine LIG at 226 nm. Linearity was obtained over 5-30, 2.5-16, 2.5-16 and 1.25-8 µg/ml for CAG, MEF, EMG and LIG, respectively. The developed methods were successfully applied for the determination of studied drugs in tablets. Validation parameters were found to be within acceptance limits, thus confirming methods accuracy and selectivity. The obtained results were statistically compared with the reported one showing no significant difference in terms of accuracy and precision. The methods could be applied for routine analysis of the cited drugs in quality control laboratories.

Resolution of overlapped spectra for the determination of ternary mixture using different and modified spectrophotometric methods.

Four new spectrophotometric methods were developed, applied to resolve the overlapped spectra of a ternary mixture of [aliskiren hemifumarate (ALS)-amlodipine besylate (AM)-hydrochlorothiazide (HCT)] and to determine the three drugs in pure form and in combined dosage form. Method A depends on simultaneous determination of ALS, AM and HCT using principal component regression and partial least squares chemometric methods. In Method B, a modified isosbestic spectrophotometric method was applied for the determination of the total concentration of ALS and HCT by measuring the absorbance at 274.5nm (isosbestic point, Aiso). On the other hand, the concentration of HCT in ternary mixture with ALS and AM could be calculated without interference using first derivative spectrophotometric method by measuring the amplitude at 279nm (zero crossing of ALS and zero value of AM). Thus, the content of ALS was calculated by subtraction. Method C, double divisor first derivative ratio spectrophotometry (double divisor (1)DD method), was based on that for the determination of one drug, the ratio spectra were obtained by dividing the absorption spectra of its different concentrations by the sum of the absorption spectra of the other two drugs as a double divisor. The first derivative of the obtained ratio spectra were then recorded using the appropriate smoothing factor. The amplitudes at 291nm, 380nm and 274.5nm were selected for the determination of ALS, AM and HCT in their ternary mixture, respectively. Method D was based on mean centering of ratio spectra. The mean centered values at 287, 295.5 and 269nm were recorded and used for the determination of ALS, AM and HCT, respectively. The developed methods were validated according to ICH guidelines and proved to be accurate, precise and selective. Satisfactory results were obtained by applying the proposed methods to the analysis of pharmaceutical dosage form.

Spectrofluorimetric determination of gemifloxacin mesylate and linezolid in pharmaceutical formulations: Application of quinone-based fluorophores and enhanced native fluorescence.

Quinone-based fluorophores and enhanced native fluorescence techniques were applied for a fast quantitative analysis of gemifloxacin mesylate (GEM) and linezolid (LIN) in pharmaceutical formulations. For this purpose, three sensitive, accurate and precise spectrofluorimetric methods were developed. GEM, as an n-electron donor, reacts with 7,7,8,8-tetracyanoquinodimethane (method A) and 2,5-dichloro-3,6-dihydroxy-p-benzoquinone (method B) as п-electron acceptors, forming charge transfer complexes that exhibit high fluorescence intensity at 441 and 390 nm upon excitation at 260 and 339 nm, respectively. Method C depends on measurement of enhanced native fluorescence of LIN in phosphate buffer (pH 5) at 380 nm upon excitation at 260 nm. Experimental factors affecting fluorescence intensity were optimized. Linearity was obtained over concentration ranges 50-500, 10-60 and 20-400 ng mL-1 for methods A, B and C, respectively. The developed methods were validated and successfully applied for determination of the cited drugs in tablets.

A validated spectrofluorimetric method for the determination of nifuroxazide through coumarin formation using experimental design.

BACKGROUND: Nifuroxazide (NF) is an oral nitrofuran antibiotic, having a wide range of bactericidal activity against gram positive and gram negative enteropathogenic organisms. It is formulated either in single form, as intestinal antiseptic or in combination with drotaverine (DV) for the treatment of gastroenteritis accompanied with gastrointestinal spasm. Spectrofluorimetry is a convenient and sensitive technique for pharmaceutical quality control. The new proposed spectrofluorimetric method allows its determination either in single form or in binary mixture with DV. Furthermore, experimental conditions were optimized using the new approach: Experimental design, which has many advantages over the old one, one variable at a time (OVAT approach). RESULTS: A novel and sensitive spectrofluorimetric method was designed and validated for the determination of NF in pharmaceutical formulation. The method was based upon the formation of a highly fluorescent coumarin compound by the reaction between NF and ethylacetoacetate (EAA) using sulfuric acid as catalyst. The fluorescence was measured at 390 nm upon excitation at 340 nm. Experimental design was used to optimize experimental conditions. Volumes of EAA and sulfuric acid, temperature and heating time were considered the critical factors to be studied in order to establish an optimum fluorescence. Each two factors were co-tried at three levels. Regression analysis revealed good correlation between fluorescence intensity and concentration over the range 20-400 ng ml-1. The suggested method was successfully applied for the determination of NF in pure and capsule forms. The procedure was validated in terms of linearity, accuracy, precision, limit of detection and limit of quantification. The selectivity of the method was investigated by analysis of NF in presence of the co-mixed drug DV where no interference was observed. The reaction pathway was suggested and the structure of the fluorescent product was proposed. Statistical comparison between the presented method and a reported spectrophotometric one was carried out on pure and pharmaceutical formulation and revealed no significant difference. CONCLUSION: The proposed method was considered economic, accurate, precise and highly sensitive. It could be easily applied in laboratory quality control for the analysis of NF in pure form and in pharmaceutical dosage form.

Validated spectrophotometric methods for the simultaneous determination of ciprofloxacin hydrochloride and metronidazole in tablets.

A binary mixture of ciprofloxacin hydrochloride (CIP) and metronidazole (MET) was determined by five simple and accurate methods, without prior separation. In the first method, CIP was determined by second derivative spectrophotometric method ((2)D) by measuring the amplitude at 282 nm (zero ordinate value of MET). On the other hand, the determination of MET was based on isosbestic point technique, where the total content of the mixture was determined at 294.5 nm (isosbestic point), then the content of MET could be calculated by subtraction. The second method was first derivative ratio spectrophotometric method ((1)DD) where the total amplitude at 261 and 285 nm and the amplitude at 295.5 nm were selected to simultaneously determine CIP and MET in binary mixture, respectively. The third method was based on dual wavelength analysis, in which two wavelengths were selected, at which the absorbances of the other component were the same. The fourth method depends on using Q-analysis method (absorbance ratio) which involves the formation of Q-absorbance equation using the respective absorptivity values at 294.5 nm (isosbestic point) and 281.5 nm (λ(max) of CIP). The fifth method is partial least-squares (PLS) chemometric technique for determination of CIP and MET. The developed methods were successfully applied to the analysis of CIP and MET in laboratory prepared mixtures and tablets with good recoveries and their validation was carried out following the International Conference on Harmonization (ICH) guidelines. The results obtained were statistically compared with each other showing no significant difference with respect to accuracy and precision.