Hadir M. Maher

Simultaneous determination of newly developed antiviral agents in pharmaceutical formulations by HPLC-DAD

BackgroundOmbitasvir/paritaprevir/ritonavir/dasabuvir (Viekira Pak®) are the newest medicines approved for use in the treatment of hepatitis C virus (HCV) and are available in tablet form as an oral combination. Specifically, these agents are indicated in the treatment of HCV in patients with genotype 1 infection. Due to the therapeutic importance and increased use of Viekira Pak, proper methods for its determination in bulk and pharmaceutical formulations must be developed.ResultsThe present study describes the development and validation of a simple, rapid, selective and economical reverse phase high performance liquid chromatography-diode array detection (HPLC-DAD) method for the simultaneous determination of paritaprevir (PAR), ombitasvir (OMB), dasabuvir(DAS) and ritonavir (RIT) in bulk and pharmaceutical preparations. The proposed method was carried out using an RPC18 column (150xa0×xa04.5xa0mm, 3.5xa0μ), with a mobile phase consisting of 10xa0mM phosphate buffer (pH 7)and acetonitrile (35:65, v/v) at a flow rate of 1xa0ml/min and a detection wavelength of 254xa0nm. Sorafenib (SOR) was selected as the internal standard to ensure that the quantitative performance was high. The method was validated based on its specificity, linearity, limit of detection, limit of quantitation, accuracy, precision, robustness and stability. The calibration curves for PAR, DAS, RIT and OMB were linear at 2.5–60, 1.25–30, 1.7–40 and 0.42–10xa0μg/ml, respectively, and all of the correlation coefficients werexa0>0.999.ConclusionsThe proposed method was successfully applied for the determination of ombitasvir/paritaprevir/ritonavir/dasabuvirin tablets, without interference from the excipient peaks. Hence, the method can be applied for the routine quality control analysis of the studied drugs, either in bulk or dosed forms.Graphical abstractSimultaneous estimation of newly developed antiviral agents in pharmaceutical formulations by HPLC-DAD method

Bioavailability study of triamterene and xipamide using urinary pharmacokinetic data following single oral dose of each drug or their combination.

An efficient chromatographic method for the simultaneous determination of triamterene (TRI) and xipamide (XIP) in urine samples, based on high performance liquid chromatography with photodiode array detector (HPLC-DAD) has been developed. The HPLC separation was performed on a RP stainless-steel C-18 analytical column (250 mm × 4.6 mm, 5 μm) with a gradient elution system of 0.05 M phosphate buffer adjusted to pH 4.0 and methanol as the mobile phase. The method was used to determine the urinary excretion profile and to calculate different urinary pharmacokinetic parameters following oral dose of their combination compared with single oral doses of each drug and hence comparing their bioavailability. Quantitation was performed using chlorthalidone as internal standard. The calibration graphs of each drug were rectilinear in the range of 0.2-40 μg/mL urine for TRI and 0.2-15 μg/mL urine for XIP. An HPLC-DAD method was also successfully developed for the simultaneous determination of the investigated drugs in pharmaceutical preparations. The methods were validated in terms of linearity, accuracy, precision, selectivity, limits of detection and quantitation and other aspects of analytical validation.

Development of validated stability-indicating chromatographic method for the determination of fexofenadine hydrochloride and its related impurities in pharmaceutical tablets

A simple reversed phase high performance liquid chromatographic method with diode array detector (HPLC-DAD) has been developed and subsequently validated for the determination of fexofenadine hydrochloride (FEX) and its related compounds; keto fexofenadine (Impurity A), meta isomer of fexofenadine (Impurity B), methyl ester of fexofenadine (Impurity C) in addition to the methyl ester of ketofexofenadine (Impurity D). The separation was based on the use of a Hypersil BDS C-18 analytical column (250 × 4.6 mm, i.d., 5 μm). The mobile phase consisted of a mixture of phosphate buffer containing 0.1 gm% of 1-octane sulphonic acid sodium salt monohydrate and 1% (v/v) of triethylamine, pH 2.7 and methanol (60:40, v/v). The separation was carried out at ambient temperature with a flow rate of 1.5 ml/min. Quantitation was achieved with UV detection at 215 nm using lisinopril as internal standard, with linear calibration curves at concentration ranges 0.1-50 μg/ml for FEX and its related compounds. The optimized conditions were used to develop a stability-indicating HPLC-DAD method for the quantitative determination of FEX and its related compounds in tablet dosage forms. The drugs were subjected to oxidation, hydrolysis, photolysis and heat to apply stress conditions. Complete separation was achieved for the parent compounds and all degradation products. The method was validated according to ICH guidelines in terms of accuracy, precision, robustness, limits of detection and quantitation and other aspects of analytical validation.

Derivative emission spectrofluorimetry for the simultaneous determination of guaifenesin and phenylephrine hydrochloride in pharmaceutical tablets

Rapid, simple and sensitive derivative emission spectrofluorimetric methods have been developed for the simultaneous analysis of binary mixtures of guaifenesin (GUA) and phenylephrine hydrochloride (PHE). The methods are based upon measurement of the native fluorescence intensity of the two drugs at λex = 275 nm in methanolic solutions, followed by differentiation using first (D1) and second (D2) derivative techniques. The derivative fluorescence intensity-concentration plots were rectilinear over a range of 0.1-2 µg/mL for both GUA and PHE. The limits of detection were 0.027 (D1, GUA), 0.025 (D2, GUA), 0.031 (D1, PHE) and 0.033 (D2, PHE) µg/mL and limits of quantitation were 0.089 (D1, GUA), 0.083 (D2, GUA), 0.095 (D1, PHE) and 0.097 (D2, PHE) µg/mL. The proposed derivative emission spectrofluorimetric methods (D1 and D2) were successfully applied for the determination of the two compounds in binary mixtures and tablets with high precision and accuracy. The proposed methods were fully validated as per ICH guidelines.

Simultaneous determination of selected tyrosine kinase inhibitors with corticosteroids and antiemetics in rat plasma by solid phase extraction and ultra-performance liquid chromatography–tandem mass spectrometry: Application to pharmacokinetic interaction studies

A sensitive and selective ultra-performance liquid chromatography-tandem mass spectrometry method has been developed and validated for the simultaneous analysis of selected tyrosine kinase inhibitors (TKIs)(gefitinib GEF, erlotinib ERL), corticosteroids (dexamethasone DEX, prednisolone PRED), and the antiemetic ondansetron (OND) in rat plasma samples. After the addition of domperidone (DOM) as internal standard (IS), spiked plasma samples were prepared using the solid phase extraction (SPE) C 18 cartridges. Chromatographic separation was performed on a Waters BEH C18 column with an isocratic elution using a mobile phase composed of acetonitrile and water, each with 0.1% formic acid, (80: 20, v/v), at a flow rate of 0.2 mL/min. Quantitation of the analytes was performed using the multiple reaction monitoring (MRM) mode with the positive ionization mode at m/z 447.25>128.08 (GEF), m/z 394.20>278.04 (ERL), m/z 393.30>147.04 (DEX), m/z 361.29>147.02 (PRED), m/z 294.18>170.16 (OND), and m/z 426.26>175.07 (DOM). The method was validated over the concentration range of 0.025-100 (GEF, ERL, OND) and 0.05-100 ng/mL plasma (PRED, DEX) with very low lower limit of quantification of 0.025 (GEF, ERL, OND) and 0.05 ng/mL (DEX, PRED). The intra- and inter-day precision (RSD%) evaluated at four different concentration levels were within the acceptable limits (<15%). The method provided good extraction recovery of all analytes from rat plasma (Er% from -14.05 to -1.08). The validated method was successfully applied to the pharmacokinetic studies following the oral administration of selected combinations of the studied drugs. This study can be readily applied in therapeutic drug monitoring (TDM) in patients receiving these drug combinations as well as investigation of possible drug interactions between TKIs and DEX/PRED/OND.

Simultaneous determination of erlotinib and tamoxifen in rat plasma using UPLC–MS/MS: Application to pharmacokinetic interaction studies

Tamoxifen (TAM) is a non-steroidal estrogen receptor antagonist that enhances erlotinib (ERL)-induced cytotoxicity in the treatment of NSCLC. ERL and TAM are metabolized by CYP3A4 enzymes. In addition, both drugs have the potential of altering the enzymatic activity through either inhibition (ERL) or induction (TAM). Thus it was expected that pharmacokinetics (PK) drug-drug interactions (DDIs) could be encountered following their co-administration. In this respect, a bioanalytical UPLC-MS/MS method has been developed and validated for the simultaneous determination of ERL and TAM in rat plasma samples, using ondansetron (OND) as an internal standard (IS). Plasma samples were prepared using mixed mode cationic solid phase extraction (SPE) STRATA™ -X-C 33μm cartridges with good extraction recovery of both drugs from rat plasma (Er% from -13.92 to -3.32). The drugs were separated on a Waters BEH™ C18 column with an isocratic elution using a mobile phase composed of a mixture of acetonitrile and water, each with 0.15% formic acid, in the ratio of 80: 20, v/v. Quantitation was carried out using the positive ionization mode with multiple reaction monitoring (MRM) at m/z 394.20>278.04 (ERL), m/z 372.25>72.01 (TAM), and m/z 294.18>170.16 (OND). The method was fully validated as per the FDA guidelines over the concentration range of 0.2-50ng/mL with very low lower limit of quantification (LLOQ) of 0.2ng/mL for both ERL and TAM. The intra- and inter-day assay precision (in terms of relative standard deviation, RSD) and accuracy (in terms of percentage relative error, % Er) were evaluated for both drugs and the calculated values evaluated at four different concentration levels were within the acceptable limits (<15%) for concentrations other than LLOQ and 20% for LLOQ. The method was successfully applied to the study of possible PK-DDI following the oral administration of ERL and TAM in a combination, compared to their single administration.

Determination of Luteolin and Apigenin in Herbs by Capillary Electrophoresis with Diode Array Detection

Capillary electrophoresis with a diode array detector was employed for the determination of luteolin and apigenin in plant extracts. The experimental factors affecting the elution of the analytes were carefully optimized. The final analysis was achieved utilizing a fused silica capillary (58 cm effective length, 75 μm ID) and a background electrolyte solution consisting of borax buffer (20 mM, pH 10.0) and methanol (90: 10, v/v) with a 23 kV driving voltage and detection at 210 nm. The method was fully validated as per the guidelines of the International Conference on Harmonization for Analytical Procedures. The relationship between peak area and concentration was linear between 3 and 800 μg/mL for both compounds with detection limits of 1.05 for luteolin and 0.53 μg/mL for apigenin. The method was employed for the determination of the analytes in extracts of thyme and parsley. Both compounds were resolved from interfering peaks that were present in the extracts. Recovery studies were performed by fortifying the extracts with standards and demonstrated good accuracy with recovery values between 97.29 and 104.88% for luteolin and 96.89 and 105.18% for apigenin. Thyme and parsley were shown to contain high concentrations of luteolin and apigenin.

HPLC-DAD STABILITY INDICATING DETERMINATION OF THE FIXED-DOSE COMBINATION OF NIFUROXAZIDE AND DROTAVERINE HYDROCHLORIDE IN CAPSULES

A simple and selective HPLC-DAD method was developed for the simultaneous determination of nifuroxazide and drotaverine hydrochloride in their combined pharmaceutical formulation. Effective chromatographic separation was achieved using a Zorbax SB-C18 (4.6 × 250 mm, 5 µm) column with gradient elution of the mobile phase composed of 0.05 M phosphoric acid and methanol. The multiple wavelength detector was set at 245, 285, and 370 nm. The retention times for nifuroxazide and drotaverine were approximately 7.5 and 10.4 min, respectively. The reliability and analytical performance of the proposed HPLC procedure were statistically validated with respect to linearity, ranges, precision, accuracy, selectivity, robustness, detection, and quantification limits. Calibration curves were linear in the range 1–40 g/mL for both nifuroxazide and drotaverine with correlation coefficients >0.9993. Both drugs were subjected to stress conditions of hydrolysis, oxidation, and photo-degradation. The proposed method proved to be stability-indicating by the resolution of the two analytes from the forced-degradation products. The validated HPLC method was applied to the analysis of this pharmaceutical mixture in capsules where the two analytes were successfully quantified with recoveries not less than 98.5%, and no interfering peaks were encountered from the inactive ingredients. Moreover, the proposed method was utilized to investigate the kinetics of the acidic and basic hydrolysis processes. The corresponding pseudo-first order rate constants and half-lives were calculated. Finally, the proposed method made use of DAD as a tool for peak identity and purity confirmation.

UPLC–ESI–MS/MS study of the effect of green tea extract on the oral bioavailability of erlotinib and lapatinib in rats: Potential risk of pharmacokinetic interaction

Green tea (GT) is one of the most consumed beverages worldwide. Tyrosine kinase inhibitors (TKIs) belong to the oral targeted therapy that gained much interest in oncology practice, among which are erlotinib (ERL) and lapatinib (LAP). Since green tea polyphenols (GTP) are known to be inhibitors of receptor tyrosine kinases, GTE could likely potentiate the anticancer effect of TKIs, but with a possibility of pharmacokinetic (PK) interaction with co-administered TKIs. In this study, the effect of GTE on the PK of ERL/LAP in rats was studied. UPLC-ESI-MS/MS method has been developed and validated for the quantification of ERL and LAP in rat plasma, using gefitinib (GEF) as the internal standard. Plasma samples were treated extensively by protein precipitation (PPT) followed by solid phase extraction (SPE) using octadecyl C 18/14% cartridges. Chromatographic analysis was carried out on Acquity UPLC BEH™ C18 column with a mobile phase consisting of water: acetonitrile (20: 80, v/v), each with 0.15% formic acid. Quantification was performed in the positive electrospray ionization (ESI+) mode with multiple reaction monitoring (MRM) of the transitions m/z 394.29→278.19 (ERL), m/z 581.07→365.13 (LAP), and m/z 447.08→128.21 (GEF). The method was fully validated as per the FDA guidelines showing linearity over the range of 0.4-1000 (ERL) and 0.6-1000 (LAP) ng/mL with very low lower limit of quantification (LLOQ) of 0.4 and 0.6ng/mL for ERL and LAP, respectively. The applicability of the method was extended to perform a comparative study of the PK of ERL/LAP following short-term and long-term administration of GTE, compared with their single oral administration. The results revealed that a significant reduction in the oral bioavailability was recorded with both ERL and LAP following the ingestion of GTE particularly for short-term administration. A reduction in Cmax (AUC) by 67.60% (69.50%) and 70.20% (73.96%), was recorded with short-term administration of GTE, compared with only 16.03% (21.09%) and 13.53% (22.12%) reduction for ERL and LAP, respectively, with long-term administration. Thus patients taking TKIs should preferably avoid drinking GT or ingesting GTE capsules during the period of treatment with TKIs.

DEVELOPMENT AND VALIDATION OF A STABILITY-INDICATING HPLC-DAD METHOD WITH ANN OPTIMIZATION FOR THE DETERMINATION OF DIFLUNISAL AND NAPROXEN IN PHARMACEUTICAL TABLETS

An artificial neural network (ANN) was employed to model the chromatographic response surface for the isocratic separation of binary mixtures of diflunisal (DFL) and naproxen (NAP). The two drugs were separated using RP-HPLC and detected with a photodiode array detector (HPLC-DAD). The ANN was trained using the composition of the mobile phase including the percentage of acetonitrile in the mobile phase and the pH of the aqueous phase as input variables while the capacity factors were used as the output variables. ANN was trained to accurately describe the retention factors of each of DFL and NAP within a defined experimental space of aqueous phase pH 2.7–5.8 and 38–60% acetonitrile in the mobile phase. Using the best performing ANN, the optimum conditions predicted were 0.05 M sodium dihydrogenphosphate aqueous solution adjusted to pH 3.4 and acetonitrile in a ratio of (50: 50, v/v). The optimized conditions were used to develop a stability-indicating HPLC method for the quantitative determination of DFL and NAP in tablet dosage forms. The drugs were subjected to oxidation, hydrolysis, photolysis, and heat to apply stress conditions. Complete separation was achieved for the parent compounds and all degradation products. The method was validated according to ICH guidelines.