Utility of sustainable ratio derivative spectrophotometry for the concurrent assay of synergistic repurposed drugs for COVID-19 infections; Insilico pharmacokinetics proof.

The cutting-edge combination of fluvoxamine (FVM) and ivermectin (IVM) has been presented as a proposed dosage form for the treatment of COVID-19 infections in early diagnosed patients. The main objective of this work is to develop simple, sensitive, and efficient methods for the synchronous quantification of FVM and IVM without any prior separation. Four green UV-methods were employed for the synchronous quantification, namely: Fourier functions convolution of absorption spectra, FFAS, Fourier functions convolution of derivative spectra of absorption curves, FFDS, Fourier function convolution of ratio spectra of absorption curves, FFRS and the dual-wavelength method, DWM. FFRS and DWM approaches can be able to reconcile the two components' significantly interfering spectrum presented in this commixture. Good linearity was checked in the range of 5-40, and 2.5-25 µg/mL for the FVM, and IVM, respectively. All approaches developed have been recommended in compliance with ICH principles. Furthermore, the approaches' greenness was predestined by "National Environmental Method Index" (NEMI), "Analytical GREEnness metric (AGREE)", the "Analytical Eco-Scale", and the "Green Analytical Procedure Index" (GAPI). In addition, spider diagram was utilized for the assessment of the greenness index of the solvent used. Beside greenness, the sustainability of our methods was investigated using the HEXAGON tool. Continuing the constant pursuit of greenness, drug-drug interactions (DDIs) between FVM & IVM were predicted by insilico tools to ensure the safety of the suggested mixture as a preliminary step before invitro and in vivo studies. Because they were deemed sustainable, affordable, and successful, the suggested UV-methods may be used for routine quality control investigations of the indicated formulations FVM & IVM.

White targeted chromatographic screening method of Molnupiravir and its metabolite with degradation kinetics characterization and in-silico toxicity.

SARS-CoV-2 virus triggered a worldwide crisis, with world nations putting up massive efforts to halt its spread. Molnupiravir (MLN) was the first oral, direct-acting antiviral drug approved for nasopharyngeal SARS-CoV-2 infection with favorable safety and tolerability profile. This study aims at determination of MLN and N4-hydroxycytidine (NHC), its main degradation product and its main metabolite, using sensitive, simple, and green HPLC-DAD method. Moreover, under different stress conditions using NaOH, HCl, neutral, H2O2, dry heat and sun light, the method was applied for MLN assay along with kinetics degradation investigation. The linearity range for MLN and NHC were both 0.1-100 µg/mL with LOD and LOQ of 0.013 & 0.043 and 0.003 & 0.011 µg/mL, for MLN and NHC, respectively. MLN was found to be extremely vulnerable to alkali hydrolysis compared with acid and dry heat degradation. In contrast, MLN was stable under conditions of oxidative, neutral, and sunlight-induced deterioration. Acid and alkali-induced degradation followed pseudo first-order kinetics model. In addition, LC-MS-UV was used to suggest the mechanism of the stress-induced degradation route and to characterize the eluted degradation products. Toxicities of both MLN and its degradation products were evaluated using ProTox-II and they were found to be negligibly harmful. The proposed HPLC-DAD was effectively used for the analysis of MLN in commercial pharmaceutical formulations. The proposed method for MLN determination after greenness and whiteness appraisal was found to be superior compared to the reported methods for MLN analysis.

Tailoring two white chromatographic platforms for simultaneous estimation of ritonavir-boosted nirmatrelvir in their novel pills: degradation, validation, and environmental impact studies.

As the COVID-19 pandemic is not yet over, Pfizer has launched the novel pill Paxlovid® (Nirmatrelvir (NMV) co-packaged with ritonavir (RIT)) as an effective medication for hospitalized and non-hospitalized patients. Making pharmaceutical analysis greener and more sustainable has lately become the main direction of the research community. In this context, two fast, green, and stability-indicating chromatographic methods were designed for the neat quantitative determination of NMV and RIT in their bulk and dosage forms. Method I is deemed the first electro-driven attempt for the assay of Paxlovid®. Herein, the optimized conditions of the Micellar Electrokinetic Chromatographic (MEKC) method were 50 mM borate buffer at pH 9.2 with 25 mM sodium lauryl sulfate (SDS) being used as the background electrolyte (BGE) on a deactivated fused silica capillary (50 cm effective length × 50 µm id). Method II was an isocratic reversed-phase HPLC separation method using Zorbax-Eclipse C18 (4.6 × 250 mm, 5 µm particle size) column and 50 mM ammonium acetate buffer at pH 5 and acetonitrile as mobile phase constituents at a flow rate of 1 mL min-1. For the sake of simplicity and increasing sensitivity, a single wavelength of 210 nm was used for the two methods to assay both drugs. Linear correlations between peak areas and concentration were observed in the ranges of 10-200 µg mL-1 for NMV and 5-100 µg mL-1 RIT in both methods. The impact of versatile stress conditions such as hydrolysis, oxidation, and photolysis on the stability of NMV and RIT was studied. Fortunately, both methodologies were able to separate both drugs from their degradants. Thus, the stability indicating power of the methods was proved. The derived methods were statistically validated in agreement with the ICH guidelines. Furthermore, the environmental friendliness and sustainability of these methods were investigated and compared with the cited methods using the holistic multicriteria evaluation tools namely Hexagon, AGREE, and RGB12 metrics. Conclusively, the proposed methods offered reliable, feasible, economic, white, and stability-indicating alternatives to the cited chromatographic methods.

Green adherent degradation kinetics study of Nirmatrelvir, an oral anti-COVID-19: characterization of degradation products using LC-MS with insilico toxicity profile.

The SARS-CoV-2 virus sets up a global catastrophe, and countries all around the world made significant efforts to halt the spread. Nirmatrelvir (NMV) was lately approved by the FDA as a safe and well-tolerated oral direct-acting antiviral medication for SARS-CoV-2 virus infection. Therefore, a fast completely validated stability indicating method was established-for the first time- for NMV determination. The study used NaOH, HCl, neutral, H2O2, and sunlight to test NMV stability under various stress conditions followed by kinetics degradation investigation and derivation of Arrhenius plot. The analysis was performed using Agilent Zorbax Eclipse-C18 column (5 µm, 4.6 × 250 mm) with a mobile phase consisting of acetonitrile: 50 mM ammonium acetate, pH = 5 (50:50, v/v, respectively) at a flow rate of 1.0 mL/min with 5 min run time. Diode array detector (DAD) was set at 225 nm to quantify NMV at the concentration range of 5-500 µg/mL with LOD and LOQ of 0.6 and 2 µg/mL, respectively. Method's greenness was assessed using different metrics including Analytical Eco-Scale, Greenness Assessment Procedure Index, GAPI, and Analytical Greenness, AGREE. A thorough study of stress stability revealed that NMV was more susceptible to alkaline hydrolysis compared with acid hydrolysis. In contrast, it was found that NMV remained stable when subjected to oxidative, neutral, and sun-induced degradation conditions. Moreover, acid and alkali-induced hydrolysis were found to follow pseudo first order kinetics. Consequently, the half lifetime of the studied degradation conditions at room temperature were calculated using the Arrhenius plot. The mechanism of the degradation pathways under stress circumstances was proposed using LC-MS-UV. Toxicities of the proposed degradation products were assessed using ProTox-II, along with the parent medication NMV, and were shown to be hardly hazardous.

An eco-friendly multi-analyte high-performance thin layer chromatographic densitometric determination of amoxicillin, metronidazole, and famotidine in their ternary mixtures and simulated gastric juice: A promising protocol for eradicating Helicobacter pylori.

Gastrointestinal tract disorders constitute a heavy burden to healthcare providers. To eradicate Helicobacter pylori infection, different triple therapy protocols have been proposed. Among which are combinations of proton pump inhibitors (e.g., omeprazole), histamine-2 receptor antagonists (e.g., famotidine), along with antibiotics (e.g., amoxicillin). In this work, a sensitive and accurate high-performance thin-layer chromatographic method was developed for the simultaneous determination of amoxicillin, metronidazole, and famotidine in bulk powder and laboratory-prepared combined-tablet mixtures. Complete separation of the cited compounds was achieved using pre-coated silica gel plates with a mixture of methanol:chloroform:toluene:water:glacial acetic acid (5:2:1.5:0.5:0.1 v/v/v/v/v) as the mobile phase. The method was fully validated as per the international conference of harmonization guidelines. Good linearity, a correlation coefficient of 0.9991, was obtained in the concentration ranges 0.1-1.6 µg/band (amoxicillin), 0.1-0.9 µg/band (metronidazole), and 0.1-0.9 µg/band (famotidine). Since the method allowed the determination of the three compounds in combined tablets with a high degree of selectivity, accuracy, precision, with cost-effectiveness, it could be used for regular quality control. Moreover, the applicability of the proposed method was extended to the determination of the ternary mixture in simulated gastric juice. Method greenness was assessed using different green metrics.

Development and validation of UPLC-MS/MS method for the simultaneous quantification of anaplastic lymphoma kinase inhibitors, alectinib, ceritinib, and crizotinib in Wistar rat plasma with application to bromelain-induced pharmacokinetic interaction.

Bromelain, the aqueous extract of pineapple, has been used as a food supplement with reported nutritional and therapeutic benefits. Bromelain has anti-cancer, anti-inflammatory, antithrombotic, and fibrinolytic effects. Anaplastic lymphoma kinase (ALK) inhibitors, including alectinib (ALC), ceritinib (CER), and crizotinib (CRZ), have been efficiently used in the management of non-small cell lung cancer (NSCLC). The solubility of ALC, CER, and CRZ is much higher at low acidic pH (pH 1) and it decreases as the pH increases affecting their absorption with a subsequent decrease in their bioavailability. It was thought that the intake of bromelain could result in a decrease in the bioavailability of ALC, CER, and CRZ due to bromelain-induced alkalizing effect following digestion. On the contrary, bromelain could possibly increase plasma exposure of the cited drugs due to its known muco-permeation enhancing effect. The therapeutic-anticancer effect of bromelain can be possibly increased/enhanced with concomitant intake of other anticancer medications or it can add to the value of food supplements for its known nutritional benefits. Thus, this work aims at studying the possibility of any PK interaction when bromelain was taken while on ALC/CER/CRZ therapy. In this work, a new UPLC-MS/MS method was developed and validated for the simultaneous determination of ALC, CER, and CRZ in rat plasma. Further application of the proposed method was performed to test the possibility of the PK interaction between bromelain and the selected ALK inhibitors in Wistar rats. Simple protein precipitation with acetonitrile was used for sample preparation. Chromatographic analysis was performed on Waters BEH™ C18 column with a mixture of acetonitrile/water containing 0.1 % formic acid (70: 30, v/v) as the mobile phase. The method permitted the analysis of ALC, CER, and CRZ in concentration ranges of 2-200, 0.4-200, and 4.0-200 ng/mL, respectively. Bromelain administration caused a significant decrease in plasma levels of CER and CRZ with lowered Cmax, AUC0-t and AUC0-∞, along with an increase in the apparent clearance. However, no significant effect was noticed with ALC. Thus, attention should be paid to avoid the intake of bromelain with CER or CRZ.

Determination of tetracycline, oxytetracycline and chlortetracycline residues in seafood products of Saudi Arabia using high performance liquid chromatography-Photo diode array detection.

Residues of oxytetracycline, tetracycline and chlortetracycline in seafood products of Saudi Arabia were detected by using a simple, sensitive and rapid method via HPLC-PDA. The protein precipitation method that was used for sample extraction demonstrated high recoveries of OTC, TC and CTC. The limits of detection were 0.015 µg/g and 0.025,0.062 µg/g for all TCs in fish and shellfish, respectively. The limits of quantitation were 0.125 µg/g and 0.175 µg/g for all TCs in fish and shellfish, respectively. The method was precise and accurate since the RSD was less than 2%, while the % recovery was 95-105%. This study determined the occurrence of OTC, TC and CTC in seafood products that are sold in KSA's markets. The overall occurrence of these three medications in 249 seafood products was 24%(n = 60), while 15%(n = 37) exceeded the MRL. Thus, our recommendations are to enhance the monitoring of food production prior to marketing and to educate people regarding the proper disposal of antibiotics.

Flavoured water consumption alters pharmacokinetic parameters and increases exposure of erlotinib and gefitinib in a preclinical study using Wistar rats.

BACKGROUND: Erlotinib (ERL) and Gefitinib (GEF) are considered first line therapy for the management of non-small cell lung carcinoma (NSCLC). Like other tyrosine kinase inhibitors (TKIs), ERL and GEF are mainly metabolized by the cytochrome P450 (CYP450) CYP3A4 isoform and are substrates for transporter proteins with marked inter-/intra-individual pharmacokinetic (PK) variability. Therefore, ERL and GEF are candidates for drug-drug and food-drug interactions with a consequent effect on drug exposure and/or drug-related toxicities. In recent years, the consumption of flavoured water (FW) has gained in popularity. Among multiple ingredients, fruit extracts, which might constitute bioactive flavonoids, can possess an inhibitory effect on the CYP450 enzymes or transporter proteins. Therefore, in this study we investigated the effects of different types of FW on the PK parameters of ERL and GEF in Wistar rats. METHODS: ERL and GEF PK parameters in different groups of rats after four weeks consumption of different flavours of FW, namely berry, peach, lime, and pineapple, were determined from plasma drug concentrations using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). RESULTS: Data indicated that tested FWs altered the PK parameters of both ERL and GEF differently. Lime water had the highest impact on most of ERL and GEF PK parameters, with a significant increase in Cmax (95% for ERL, 58% for GEF), AUC0-48 (111% for ERL, 203% for GEF), and AUC0-∞ (200% for ERL, 203% for GEF), along with a significant decrease in the apparent oral clearance of both drugs (65% for ERL, 67% for GEF). The order by which FW affected the PK parameters for ERL and GEF was as follows: lime > pineapple > berry > peach. CONCLUSION: The present study indicates that drinking FW could be of significance in rats receiving ERL or GEF. Our results indicate that the alteration in PKs was mostly recorded with lime, resulting in an enhanced bioavailability, and reduced apparent oral clearance of the drugs. Peach FW had a minimum effect on the PK parameters of ERL and no significant effect on GEF PKs. Accordingly, it might be of clinical importance to evaluate the PK parameters of ERL and GEF in human subjects who consume FW while receiving therapy.

Development and validation of UPLC-MS/MS method for studying the pharmacokinetic interaction of dasabuvir and tamoxifen, 4-hydroxytamoxifen in Wistar rats.

Hepatitis C virus (HCV) is the main cause of chronic hepatitis and probably liver cirrhosis. Dasabuvir (DSV) is a direct-acting antiviral agent with efficiency in managing HCV. The anti-viral activity of the anti-estrogen drug tamoxifen (TAM) suggested the synergistic effect of DSV and TAM for blocking the replication of HCV. However, being substrates and inhibitors of efflux transporters (TAM inhibits P-gp, DSV inhibits P-gp and BCRP), there is a possibility for a pharmacokinetic (PK) drug-drug interaction. In this work, a new UPLC-MS/MS method was developed and validated for the simultaneous determination of TAM, its active metabolite 4-hydroxy tamoxifen (TOH), and DSV in rat plasma. The method was applied to investigate the PK interaction between DSV and TAM/TOH following the co-administration of DSV and TAM to Wistar rats. Chromatographic analysis was performed on Waters BEHTM C18 column using a mobile phase of acetonitrile/water containing 0.1% formic acid (80: 20, v/v). The method allowed the determination of concentration ranges 20-1000, 0.1-500, 0.5-500 ng/mL for DSV, TAM, and TOH, respectively. Unexpectedly, results revealed the absence of PK interactions between DSV and TAM/TOH, compared with their single administration, suggesting the safety of co-administering DSV/TAM as an anti-viral combination without the need of dosage adjustment.

A Pharmacokinetic Interaction Study of Sorafenib and Iced Teas in Rats Using UPLC-MS/MS: An Illustration of Beverage-Drug Interaction.

Iced teas (ITs), also known as ready-to-drink teas, have gained much popularity among many nations. The modulatory effect of tea beverages on CYP3A4 increases the possibility of their potential interactions with many coadministered medications. Being a substrate of CYP3A4, sorafenib (SOR), the first-line therapy for the treatment of hepatocellular carcinoma, shows a great probability to exhibit pharmacokinetic (PK) interaction with ITs. For this purpose, different groups of Wistar rats were given oral doses of SOR (40 mg/kg), along with different types of ITs. The concentration of SOR in rat plasma was determined using UPLC-MS/MS. Chromatographic analysis was performed on a C18 analytical column, Acquity UPLC BEH™ (100 × 1.0 mm, i.d., 1.7 µm particle size), using erlotinib (ERL) as an internal standard. Isocratic elution was performed with a mobile phase consisting of two solvents: solvent A (water with 0.1% formic acid) and solvent B (acetonitrile with 0.1% formic acid), in a ratio of 30 : 70, v/v, respectively. Quantitation was performed using MRM of the transitions from protonated precursor ions [M+H]+ to product ions at m/z 465.12 > 252.02 (SOR) and m/z 394.29 > 278.19 (ERL). The method was fully validated as per the FDA guidance for bioanalytical method validation in the concentration range of 2.5-500 ng/mL. Different PK parameters were calculated for SOR in all rat groups and groups administered with ITs and SOR, compared with groups with simply water and SOR. Experimental data revealed that ITs caused a general reduction in SOR bioavailability; an approximate reduction of 30% was recorded for all types of tested ITs. These data indicate that ITs could affect the PK profile of SOR in rats.

UPLC-MS/MS study of the effect of dandelion root extract on the plasma levels of the selected irreversible tyrosine kinase inhibitors dasatinib, imatinib and nilotinib in rats: Potential risk of pharmacokinetic interactions.

Tyrosine kinase inhibitor treatments for chronic myeloid leukaemia based on nilotinib (NIL), dasatinib (DAS) and imatinib (IMA) have improved patient quality of life and have turned chronic myeloid leukemia from a fatal disease into a chronic disease. Dandelion is a rich source of phenolic compounds with strong biological properties, and the effects of using this plant in the treatment of different illnesses can be linked to the presence of various polyphenols found in the different parts of the plant. Thus, dandelion can potentially be used as a nutraceutical (dietary antioxidant) to prevent different disorders associated with oxidative stress, i.e. cardiovascular disorders, cancer and inflammatory processes. Mutual interference between a drug and a food constituent may result in altered pharmacokinetics of the drug and undesired or even dangerous clinical situations. In the present study, a bioanalytical ultra performance liquid chromatography-tandem mass spectrometer (UPLC-MS/MS) method was developed and validated for the quantification of DAS, IMA and NIL in rat plasma. Sample preparation was carried out using solid-phase extraction with C18 cartridges with a good extraction recovery of ≥94.37% for the three drugs. The method was fully validated as per the US Food and Drug Administration guidelines.

Physical and chemical screening of honey samples available in the Saudi market: An important aspect in the authentication process and quality assessment.

Honey is becoming accepted as a reputable and effective therapeutic agent by practitioners of conventional medicine and by the general public. It has many biological activities and has been effectively used in the treatment of many diseases, e.g. gastrointestinal diseases, skin diseases, cancer, heart diseases, and neurological degeneration. Honey is an excellent source of energy containing mainly carbohydrates and water, as well as, small amounts of organic acids, vitamins, minerals, flavonoids, and enzymes. As a natural product with a relatively high price, honey has been for a long time a target for adulteration. The authenticity of honey is of great importance from commercial and health aspects. The study of the physical and chemical properties of honey has been increasingly applied as a certification process for the purpose of qualification of honey samples. The current work focusses on studying the authenticity of various types of honey sold in Riyadh market (24 samples). For this purpose, physical properties (pH, hydroxylmethylfurfural HMF, and pollen test) were measured. Besides, sugar composition was evaluated using Fehling test and an HPLC method. Elemental analysis was carried out using inductively coupled plasma (ICP). In addition, the presence of drug additives was assessed by means of GC-MS. The obtained results were compared with the Saudi Arabian standards, Codex Alimentarius Commission (2001), and harmonized methods of the international honey commission.

Ultra-performance LC-MS/MS study of the pharmacokinetic interaction of imatinib with selected vitamin preparations in rats.

AIM: The growing interest of cancerous patients in using vitamins, while on imatinib (IMA) therapy, increased the risk of their pharmacokinetic interactions. METHODOLOGY: Ultra-performance LC-MS/MS method was developed and validated for the determination of IMA following oral administration of selected vitamin preparations (vitamin A, E, D3 and C) in rat plasma using a hybrid sample preparation technique of protein precipitation followed by SPE. RESULTS: The method showed good linear response for IMA over the concentration range 1-500 ng/ml. Co-administered vitamin preparations could affect IMA pharmacokinetic profiling through either an increase (vitamin A and E) or a decrease (vitamin C) in IMA bioavailability. Vitamin D3 produced no significant effect on IMA bioavailability. CONCLUSION: Particular concern should be paid when vitamin preparations are administered with IMA.

Validated UPLC-MS/MS method for the quantification of dasatinib in plasma: Application to pharmacokinetic interaction studies with nutraceuticals in Wistar rats.

Dasatinib (DAS) is a tyrosine kinase inhibitor (TKI) used in the treatment of chronic myeloid leukemia and in the management of ulcerative colitis (UC). Since some nutraceuticals (e.g. curcumin, olive oil, and cocoa extract) could alter the function of ABC transporters and /or CYP450 enzymes, DAS bioavailability could potentially be affected following their co-administration. This work aims at studying the possibility of PK interaction between DAS and the selected nutraceuticals in UC rats using UPLC- MS/MS. Chromatographic analysis was carried out using BEH C 18 column (Waters) with a mobile phase consisting of acetonitrile and 50% aqueous methanol, 65:35, v/v, each with 0.1% formic acid and using erlotinib (ERL) as an internal standard (IS). DAS quantitation was carried out using multiple reaction monitoring (MRM) with positive ionization of the transitions at m/z 488.03 > 400.92 (DAS), and m/z 394.29 > 278.19 (ERL). Method validation was assessed as per the FDA guidelines for bioanalytical methods for DAS determination within the concentration range 1-500 ng/mL. No significant effect on the oral bioavailability of DAS was reported with any of the studied nutraceuticals. Thus, the concomitant administration of these nutraceuticals with DAS could be considered safe with a necessity to perform more detailed clinical investigations.

Micelle-enhanced direct spectrofluorimetric method for the determination of linifanib: Application to stability studies.

A new simple stability-indicating spectrofluorimetric method has been developed and validated for the determination of the tyrosine kinase inhibitor, linifanib (LNF). The proposed method makes use of the native fluorescence characteristics of LNF in a micellar system. Compared with aqueous solutions, the fluorescence intensity of LNF was greatly enhanced upon the addition of Tween-80. The relative fluorescence intensity of LNF was measured in a diluting solvent composed of 2% Tween-80: phosphate buffer pH 8.0 (20: 80, v/v) using excitation and emission wavelengths of 290 and 450 nm, respectively. The proposed method was fully validated as per the ICH guidelines. The recorded fluorescence intensity of LNF was rectilinear over a concentration range of 0.3-2 µg/ml with a high correlation coefficient (r = 0.9990) and low limits of detection (0.091 µg/ml) and quantitation (0.275 µg/ml). The applicability of the method was extended to study the inherent stability of LNF under different stress degradation conditions including, alkaline, acidic, oxidative, photolytic and thermal degradation. Moreover, the method was utilized to study the kinetics of the alkaline and oxidative degradation of LNF. The pseudo-first order rate constants and half-lives were calculated.

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.

Comparative pharmacokinetic profiles of selected irreversible tyrosine kinase inhibitors, neratinib and pelitinib, with apigenin in rat plasma by UPLC-MS/MS.

Neratinib (NER) and pelitinib (PEL) are irreversible tyrosine kinase inhibitors (TKIs) that have been recently employed in cancer treatment. Apigenin (API), among other flavonoids, is known to have antioxidant, anti-proliferative, and carcinogenic effect. API can potentiate the antitumor effect of chemotherapeutic agents and/or alleviate the side effects of many anticancer agents. Since TKIs are mostly metabolized by CYP3A4 enzymes and that API could alter the enzymatic activity, potential drug interactions could be expected following their co-aministration. In the present study, a bioanalytical UPLC-MS/MS method has been developed and validated for the quantification of NER and PEL in rat plasma, using domperidone (DOM) as an internal standard. Sample preparation was carried out using solid phase extraction (SPE) with C18 cartridges with good extraction recovery of not less than 92.42% (NER) and 89.73% (PEL). Chromatographic analysis was performed on a Waters BEH C18 column with a mobile phase composed of acetonitrile and water, (70:30, v/v), each with 0.1% formic acid. Quantitation was performed using multiple reaction monitoring (MRM) of the transitions from protonated precursor ions [M+H]+, at m/z 557.30 (NER), m/z 468.21 (PEL), and at m/z 426.27 (DOM), to selected product ions at m/z 112.05 (NER), m/z 395.22 (PEL), and at m/z 175.18 (DOM). The method was fully validated as per the FDA guidelines over the concentration range of 0.5-200ng/mL with very low lower limit of quantification (LLOQ) of 0.5ng/mL for both NER and PEL. The intra- and inter-day assay precision and accuracy were evaluated for both drugs and the calculated values of percentage relative standards deviations (%RSD) and relative errors (%Er) were within the acceptable limits (<15%) for concentrations other than LLOQ and 20% for LLOQ. The applicability of the method was extended to study the possibility of drug interactions following the oral co-administration of NER/PEL with API. Thus, this study could be readily applied in therapeutic drug monitoring (TDM) of cancerous patients receiving such drug combinations.

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.

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.

Chemometrics-assisted Spectrofluorimetric Determination of Two Co-administered Drugs of Major Interaction, Methotrexate and Aspirin, in Human Urine Following Acid-induced Hydrolysis.

Methotrexate (MTX) is widely used to treat rheumatoid arthritis (RA), mostly along with non-steroidal anti-inflammatory drugs (NSAIDs), the most common of which is aspirin or acetyl salicylic acid (ASA). Since NSAIDs impair MTX clearance and increase its toxicity, it was necessary to develop a simple and reliable method for the monitoring of MTX levels in urine samples, when coadministered with ASA. The method was based on the spectrofluorimetric measurement of the acid-induced hydrolysis product of MTX, 4-amino-4-deoxy-10-methylpteroic acid (AMP), along with the strongly fluorescent salicylic acid (SA), a product of acid-induced hydrolysis of aspirin and its metabolites in urine. The overlapping emission spectra were resolved using the derivative method (D method). In addition, the corresponding derivative emission spectra were convoluted using discrete Fourier functions, 8-points sin xi polynomials, (D/FF method) for better elimination of interferences. Validation of the developed methods was carried out according to the ICH guidelines. Moreover, the data obtained using derivative and convoluted derivative spectra were treated using the non-parametric Theil's method (NP), compared with the least-squares parametric regression method (LSP). The results treated with Theil's method were more accurate and precise compared with LSP since the former is less affected by the outliers. This work offers the potential of both derivative and convolution using discrete Fourier functions in addition to the effectiveness of using the NP regression analysis of data. The high sensitivity obtained by the proposed methods was promising for measuring low concentration levels of the two drugs in urine samples. These methods were efficiently used to measure the drugs in human urine samples following their co-administration.