Simultaneous determination of atorvastatin, metformin and glimepiride in human plasma by LC-MS/MS and its application to a human pharmacokinetic study

Validation and Application of Screen-Printed Microchip for Potentiometric Determination of Metformin Hydrochloride in Tablet Dosage Form

Metformin is an oral biguanides hypoglycaemic agent, which used to lower the blood glucose levels in people with type 2 diabetes mellitus. Many analytical techniques have been used to quantify the drug in different pharmaceutical dosage forms; however, most of these methods have limited throughput in the quality control application. A disposable potentiometric microsensor responsive to metformin has recently been reported. For the first time, herein, this method of analysis has been validated according to IUPAC recommendations and successfully applied in the determination of metformin drug in some dosage form. Different drug formulations of metformin hydrochloride have been collected from the local pharmaceutical stores in Saudi Arabia and analysed using the validated microchip-based method of analysis. Subsequently, the results of this study showed that the validated method was linear, specific, precise, and accurate. The linear range was 1 × 10-1-1 × 10-5 mol L-1 and the correlation coefficient was 0.999. The limit of detection was 2.89 × 10-6 mol L-1, and the limit of quantification was 8.77 × 10-6 mol L-1. This method demonstrated high precision, with an RSD% of less than 2.22%. The accuracy of this method was obtained by comparing the recovery percentage with percentage values less than 5%. The results obtained showed that there was no significant difference between the references, label, and recovery of less than 5%.

GC Analysis of Metformin, Ranitidine and Famotidine from Pharmaceuticals and Human Serum

A method has been designed based on gas chromatography with flame ionization detection (FID) for the separation and analyses of ranitidine, famotidine and metformin after pre-column derivatization with trifluoroacetylacetone and ethyl chloroformate. DB-1 (30 m × 0.32 mm id) column with film thickness 0.25 μm was used for the separation at an initial temperature of column was 100°C for 2 min, and ramping at 20°C/min up to 250°C, with a hold time of 3 min. The rate of nitrogen flow was 2.5 mL/min and FID was used for detection. Complete separation was obtained between all the three drugs including excess of derivatization reagents. Linear calibration curves and detection limits were obtained in the ranges 0.1-30 μg/mL and 0.011-0.015 μg/mL. The procedure was repeatable in terms of peak heights/peak areas and retention time (n = 5) for derivatization, quantitation and separation with relative standard deviations (RSDs) within 2.0-3.0%. The approach was examined for the analyses of drug products and serum after the intake of the drugs by healthy volunteers, and recoveries were obtained within 95-98% with RSDs 2.4-3.1%.

Bioanalytical LC-MS/MS method for simultaneous estimation of atorvastatin, its major active metabolites and ezetimibe

Background: Hyperlipidemia is one of the most common chronic diseases encountered globally, and atorvastatin (ATV) is mainly metabolized into two major active metabolites. Methodology: Hence, we aimed to estimate ATV and ezetimibe (EZE) simultaneously in the presence of ATV major and active metabolites using a validated LC-MS/MS method. Conclusion: The proposed method was linear (r² >0.99), accurate (92.02-109.94%) and precise (CV% ≤14) over the concentration range of 0.50-120 ng/ml, 0.20-48 ng/ml, 0.50-120 ng/ml and 0.20-48 ng/ml for ATV, EZE, 2-hydroxy ATV and 4-hydroxy ATV, respectively. The applied liquid-liquid extraction gave rise to reliable extraction recoveries of 84.91 ± 1.14%, 85.20 ± 1.62%, 85.46 ± 0.41% and 105.46 ± 2.35% for ATV, EZE, 2-hydroxy ATV and 4-hydroxy ATV, respectively.

Spectrophotometric methods for determination of glimepiride and pioglitazone hydrochloride mixture and application in their pharmaceutical formulation

Simple, accurate, and precise four spectrophotometric methods were developed and validated for simultaneous determination of glimepiride and pioglitazone hydrochloride in their pharmaceutical formulation. The first spectrophotometric method was the dual-wavelength which determined glimepiride at 219.0 and 228.0 nm and pioglitazone hydrochloride at 268.0 nm. The second one is the first derivative of ratio spectra (DD1) spectrophotometry in which the peak amplitudes were used at 238.0 nm and 268.0 nm for glimepiride and pioglitazone hydrochloride, respectively. The third method is ratio subtraction in which glimepiride was determined at 228.0 nm in the presence of pioglitazone hydrochloride which was determined by extended ratio subtraction at 268.0 nm. The fourth method was the ratio difference to determine glimepiride and pioglitazone hydrochloride. Beer's law was confirmed in the concentration range 2.50-15.00 µg mL-1, and 10.00-50.00 µg mL-1 for glimepiride and pioglitazone respectively for the four methods. The proposed methods were used to determine both drugs in their pure powdered form with mean percentage recoveries of 99.91 ± 1.117% for glimepiride and 99.76 ± 0.911% for pioglitazone hydrochloride in method (A). In method (B), the mean percentage recoveries were 100.12 ± 0.89% for glimepiride and 100.02 ± 1.06% for pioglitazone hydrochloride. In method (C) glimepiride was 100.01 ± 0.592% and 99.85 ± 0.845% for pioglitazone hydrochloride by extended ratio subtraction. And finally, in method (D) the mean percentage recoveries were 100.66 ± 0.670% for glimepiride and 99.92 ± 0.988% for pioglitazone hydrochloride. The developed methods were successfully applied for the determination of glimepiride and pioglitazone hydrochloride in pure powder and dosage form. The suggested methods were also used to determine both compounds in laboratory-prepared mixtures. The accuracy, precision, and linearity ranges of the developed methods were determined. The results obtained were compared statistically with the official method, and there was no significant difference between the proposed methods and the official method for accuracy and precision.

Development and Greenness Assessment of HPLC Method for Studying the Pharmacokinetics of Co-Administered Metformin and Papaya Extract

Foods with medical value have been proven to be beneficial, and they are extensively employed since they integrate two essential elements: food and medication. Accordingly, diabetic patients can benefit from papaya because the fruit is low in sugar and high in antioxidants. An RP-HPLC method was designed for studying the pharmacokinetics of metformin (MET) when concurrently administered with papaya extract. A mobile phase of 0.5 mM of KH2PO4 solution and methanol (65:35, v/v), pH = 5 ± 0.2 using aqueous phosphoric acid and NaOH, and guaifenesin (GUF) were used as an internal standard. To perform non-compartmental pharmacokinetic analysis, the Pharmacokinetic program (PK Solver) was used. The method's greenness was analyzed using two tools: the Analytical GREEnness calculator and the RGB additive color model. Taking papaya with MET improved the rate of absorption substantially (time for reaching maximum concentration (Tmax) significantly decreased by 75% while maximum plasma concentration (Cmax) increased by 7.33%). The extent of absorption reduced by 22.90%. Furthermore, the amount of medication distributed increased (30.83 L for MET concurrently used with papaya extract versus 24.25 L for MET used alone) and the clearance rate rose by roughly 13.50%. The results of the greenness assessment indicated that the method is environmentally friendly. Taking papaya with MET changed the pharmacokinetics of the drug dramatically. Hence, this combination will be particularly effective in maintaining quick blood glucose control.

A review on liquid chromatographic methods for the bioanalysis of atorvastatin

Background

The unsatisfied clinical need has encouraged the development and validation of bioanalytical procedures for the quantification of drugs in biological samples because the monitoring of drug concentrations helps in personalizing the patient’s pharmacotherapy, assessing the adherence to therapy, and is also extensively useful for pharmacokinetics and drug-drug interactions studies.

Main Body

The present review aimed to provide insightful information about the various liquid chromatographic methods developed till 2019 for the analysis and quantification of atorvastatin, its metabolites, and co-administered drugs in the various biological matrices like the serum, plasma, and urine with special emphasis on sample preparation techniques applied before chromatographic analysis along with different chromatographic conditions and their validation data. A total of 88 published papers that have used liquid chromatography techniques to quantify atorvastatin in biological fluids are included in the study. Out of the total reported liquid chromatographic methods, 34% used UV spectrophotometer as a detector, and 55% used MS/MS as a detector. Whereas 38% of them used protein precipitation procedure, 33% applied liquid-liquid extraction approach, and 12% employed solid-phase extraction technique for sample preparation.

Conclusion

In the last decade, numerous bioanalytical procedures have been developed for the quantification of atorvastatin in different biological samples using liquid chromatographic techniques. Moreover, advancement in technology developed several new and advanced sample preparation approaches like dispersive liquid-liquid extraction, microextraction by packed sorbent, which have high recovery rates than conventional procedures. Thus, the summarized review may be consulted as an informative tool to support the optimization of new bioanalytical methods for the quantification of atorvastatin.

Method development for quantitative determination of seven statins including four active metabolites by means of high-resolution tandem mass spectrometry applicable for adherence testing and therapeutic drug monitoring

Background Statins are used to treat and prevent cardiovascular diseases (CVDs) by reducing the total serum cholesterol concentration. Unfortunately, dose-related side effects and sub-optimal response, attributed to non-adherence amongst others, were described. Therefore, a fast and sensitive liquid chromatography-high-resolution tandem mass spectrometry (LC-HRMS/MS) method for adherence testing and therapeutic drug monitoring of all currently marketed statins and their active metabolites in human blood plasma should be developed, validated and tested for applicability. Methods Atorvastatin, fluvastatin, lovastatin, pitavastatin, pravastatin, rosuvastatin, and simvastatin, as well as ortho- and para-hydroxy-atorvastatin, lovastatin hydroxy acid and simvastatin hydroxy acid were included and several internal standards (IS) tested. Validation was performed according to the guideline of the European Medicines Agency including selectivity, carry-over, accuracy, precision, matrix effects, dilution integrity and analyte stability. Finally, applicability was tested using 14 patient samples submitted for regular toxicological analysis. Results Due to an analytical interference of atorvastatin-d5, diazepam-d5 and pentobarbital-d5 were chosen as IS for positive and negative ionization mode, respectively. All statins and metabolites fulfilled the validation acceptance criteria except for fluvastatin, which could not be quantified reliably and reproducibly, most probably due to instability. Analyses of human plasma samples revealed concentrations of statins and metabolites below the reference plasma concentrations in the case of eight patients. However, nothing was known concerning patients' adherence and time between intake and sampling. Conclusions An LC-HRMS/MS method for identification and quantification of atorvastatin, lovastatin, pitavastatin, pravastatin, rosuvastatin, simvastatin and four active metabolites was successfully developed and applicability demonstrated.

Pharmacokinetics and Pharmacodynamic Herb-Drug Interaction of Piperine with Atorvastatin in Rats

Herbals that are widely consumed as therapeutic alternatives to conventional drugs for cardiovascular diseases, may lead to herb-drug interactions (HDIs). Atorvastatin (ATR) is drug of choice for hyperlipidemia and is extensively metabolized through CYP3A4 enzyme. Thus, we postulate that concomitant administration of ATR with piperine (PIP, potent inhibitor of CYP3A4 enzyme)/ridayarishta (RID, cardiotonic herbal formulations containing PIP) may lead to potential HDI. A simple, accurate, sensitive high-performance liquid chromatography-photodiode array detection method using Kromasil-100 C18 column, mobile phase acetonitrile: 30 mM phosphate buffer (55:45 v/v) pH 4.5 with flow rate gradient programming was developed to study the potential HDI in rats. Method was found to be linear (2-100 ng/mL) with Lower Limit of Detection (LLOD) 2 ng/mL. The precision (%CV < 15%), accuracy (-1.0 to -10% R.E) with recoveries above 90% from rat plasma of ATR and IS were obtained. The pharmacokinetic (PK) interactions studies on co-administration of ATR (8.4 mg/kg, p.o.) with PIP (35 mg/kg, p.o.), demonstrated a threefold increase in Cmax of ATR (P < 0.01) with significant increase in AUC0-t/AUC0-∞ compared to ATR alone indicating potential PK-HDI. However co-administration of RID (4.2 mL/kg, p.o.) showed less significant changes (P > 0.05) indicating low HDI. The pharmacodynamic effects/interactions study (TritonX-100 induced hyperlipidemic model in rats) suggested no significant alterations in the lipid profile on co-administration of PIP/RID with ATR, indicating that there may be no significant pharmacodynamic interactions.

Ecological HPLC method for analyzing an antidiabetic drug in real rat plasma samples and studying the effects of concurrently administered fenugreek extract on its pharmacokinetics

Currently, the total number of diabetic people worldwide is constantly increasing. Metformin (MET) is known to be a first-line antidiabetic drug with varied, wide-reaching applications. Concurrent administration of phytomedicines such as fenugreek extract with synthetic drugs is very common. It is reported that concomitant administration of fenugreek extract with metformin maintains lower blood glucose levels than metformin alone. In this work, an ecofriendly RP-HPLC method was established to study and compare the pharmacokinetics of metformin with and without the contemporary administration of fenugreek extract using rat as an animal model. In the developed method, a solvent mixture of 0.5 mM KH₂PO₄ solution : methanol (65 : 35, v/v) was used as a mobile phase and guaiphenesin was used as an internal standard. The plasma concentration–time curve was plotted, and non-compartmental pharmacokinetic analysis was performed using PKSolver. The results of the pharmacokinetic study showed that concurrent administration of fenugreek significantly increased the bioavailability of metformin and doubled the time required to reach the peak plasma concentration (T_max). Moreover, the volume of drug distribution decreased by about 70%, while its rate of clearance decreased by about 55.96%. Accordingly, the administration of fenugreek in combination with metformin significantly affected the pharmacokinetics of metformin, and this combination will be very useful in controlling blood glucose levels in diabetic patients. The greenness of the method was assessed using the Analytical Eco-Scale, Analytical Method Volume Intensity (AMVI), and National Environmental Method Index (NEMI), and all results affirmed that the method can be considered to be ecological.

The combination of fenugreek extract and metformin can be considered as an auspicious treatment for satisfactory diabetes control and minimizing the expected long-term complications of metformin.

TLC-spectrodensitometric method for simultaneous determination of dapagliflozin and rosuvastatin in rabbit plasma: stability indicating assay and kinetic studies

Herein, a sensitive and reliable eco-friendly TLC-spectrodensitometric method has been established for the simultaneous determination of dapagliflozin (DAPA) and rosuvastatin (ROSV) for the first time. TLC separation was carried out on silica gel F254 using ethyl acetate : methanol (5 : 0.1, v/v) as a mobile phase and UV measurement at 243 nm. The method was fully validated according to ICH guidelines. Acceptable separation was achieved with R f values of 0.23 and 0.44 for DAPA and ROSV, respectively. Regression plots revealed linear relationships in the concentration range 20-2500 ng per band and 10-2500 ng per band with LODs of 6.60 and 3.57 ng per band for both DAPA and ROSV, respectively. The relative standard deviations (RSDs%) were found to be 1.35 and 0.53 for DAPA and ROSV, respectively. Moreover, kinetic studies were conducted for measurement of degradation rate constant (k) and half life time (t 1/2) of DAPA and ROSV via forced photo-degradation.

Comparative Study of Different Derivative Spectrophotometric Techniques for the Analysis and Separation of Metformin, Empagliflozin, and Glimepiride

Background:

In some cases, lifestyle changes are not enough to keep type 2 diabetes under control, so there are several medications that may help. Metformin can lower your blood sugar levels, Glimepiride makes more insulin, whereas Empagliflozin prevents the kidneys from reabsorbing sugar into the blood and sending it out in the urine.

Methods:

Mean centering, double divisor, ratio spectra-zero crossing, and successive derivative were applied for the estimation of metformin, empagliflozin, and glimepiride respectively, in their prepared laboratory mixtures and in pharmaceutical tablets, without prior chemical separation. The absorption spectra of the mentioned drugs were recorded in the range of 200-400nm.

Results:

These methods were linear over concentration ranges of 1.0-10, 2.5-30, and 1.0-10 μgmL-1 of metformin, empagliflozin, and glimepiride respectively. Mean centering for metformin was measured at 234 and 248 nm, while empagliflozin and glimepiride had amplitude values at 276 and 262 nm, respectively. The derivative of double divisor was measured at 234, 278, and 288 nm for metformin, empagliflozin and glimepiride, respectively. The ratio of spectra-zero crossing was quantified at amplitude values of the analytical signal at 234 and 274 nm for metformin and empagliflozin, respectively, whereas glimepiride was determined at 242 and 286 nm. The successive ratio of metformin, empagliflozin, and glimepiride was determined at 284, 242, and 266 nm, respectively.

Conclusion:

The methods are validated according to the ICH guidelines where accuracy, precision and repeatability are found to be within the acceptable limit. The methods were studied and optimized. Upon validation linearity, precision, accuracy, LOD, LOQ and selectivity were proved to be operative for the analysis of specified drugs in pharmaceutical dosage configuration. Statistical illustration was done between the suggested methods with the reported methods with consideration to accuracy and precision. No significant difference was found by student’s t-test, F-test and one-way ANOVA.

Ecofriendly chromatographic methods for determination of co-prescribed drugs, olanzapine and metformin, in rat plasma

Background: Olanzapine (OLZ) is one of most recommended drugs for the treatment of schizophrenia while metformin (MET) is the most commonly used hypoglycemic agent. Aim: Development and validation of two green, sensitive and accurate chromatographic methods for the simultaneous determination of OLZ along with the co-prescribed, MET. Materials & methods: TLC-densitometric method with a developing system consisting of methylene chloride:methanol:ethyl acetate:triethylamine (4:4:5:0.1, by volume) and a reversed-phase (RP)-HPLC method where the chromatographic separation was performed using ethanol:water mixture (50: 50, v/v) as a mobile phase. Results: TLC-densitometric method had linearity over concentration ranges of 160-4000 ng/band for OLZ and 150-4500 ng/band for MET, while RP-HPLC method was linear and validated over concentration range of 300-20000 ng/ml for OLZ and MET. Conclusion: Pharmacokinetic study was successfully performed and suggested the possibility of co-administration of MET with OLZ and their further formulation in one pharmaceutical preparation to enhance patient's compliance.

LC-MS/MS method for simultaneous determination of rivaroxaban and metformin in rat plasma: application to pharmacokinetic interaction study

Aim: A reliable, sensitive and simple LC-MS/MS method has been established and validated for the quantitation of rivaroxaban (RIV) and metformin (MET) in rat plasma. Results: The procedure of method validation was conducted according to the guiding principles of EMA and US FDA. At the same time, the method was applied to pharmacokinetic interactions study between RIV and MET for the first time. When RIV and MET coadministered to rats, pharmacokinetic parameters of MET like AUC_(0-t), AUC_(0-∞) and C_max had statistically significant increased. t_max of RIV was prolonged without affecting t_1/2 obviously and C_max was inhibited significantly (p < 0.05) by comparison to the single group. Conclusion: The results indicated that drug-drug interactions occurred when the coadministration of RIV and MET.

Screening of herbal medicines for potential allopathic antidiabetic adulterants: An analytical study

Background:

There are several reports worldwide on adulteration of herbal medicines (HMs) with allopathic drugs. In India, only a few studies have reported adulteration of HMs with antidiabetics and there are no systematic studies.

Aims:

To develop a rapid and validated method for detection of allopathic antidiabetic adulterants and to explore the extent of adulteration in HMs sold in South India.

Materials and Methods:

Standards and solvents were purchased from Sigma-Aldrich. Different brands of antidiabetic HM samples with manufacturing licenses were procured from dispensaries. Spiked drug free psyllium husk as solid and flask seed oil as liquid herbal matrices were used for method development. The spiked matrices with different concentrations were extracted with methanol and subjected to centrifugation. The supernatant was collected and analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Isocratic elution was carried on a C18 column with 0.1% (v/v) formic acid:methanol (3:7, v/v) as a mobile phase. All drugs were monitored for two ion products in positive electrospray ionization mode using multiple reaction monitoring scans.

Results:

The retention time was 9 min. Limit of detection is 10 Pictograms (pg) for all analytes except for metformin, which was 370 pg. Recoveries of analytes range from 96% to 117%. Forty different brands of antidiabetic HMs were analyzed. Adulterant peaks were not observed in the mass chromatograms of HMs.

Conclusions:

A single-run method was developed by LC-MS/MS for the detection of proposed antidiabetics in HMs from licensed manufacturing units and online sold HMs across herbal dispensaries in Puducherry union territory, India. None of the HMs was found to be adulterated with proposed allopathic antidiabetic adulterants.

Development, Validation and Application of HPLC Method for Metformin in Rabbit Plasma

Objective:

This study was aimed at conducting a pharmacokinetic evaluation of metformin in rabbit plasma samples using rapid and sensitive HPLC method and UV detection.

Methods:

Acetonitrile was used for protein precipitation in the preparation of plasma samples. Reverse phase chromatography technique with silica gel column (250 mm × 4.6 mm, 5 μm) at 30°was used for the separation purpose. Methanol and phosphate buffer (pH 3.2) mixture was used as a mobile phase with flow rate 0.8 ml/min. The wavelength of UV detector was adjusted at 240 nm.

Results:

The calibration curve was linear in a range of 0.1-1 µg/ml with R² = 0.9982. The precision (RSD, %) values were less than 2%, whereas, accuracy of method was higher than 92.37 %. The percentage recovery values ranged between 90.14 % and 94.97 %. LOD and LOQ values were 25 ng/ml and 60 ng/ml, respectively. Cmax and AUC0-t values were found to be 1154.67 ± 243.37 ng/ml and 7281.83 ± 210.84 ng/ml.h, respectively after treating rabbits with a formulation containing 250 mg metformin.

Conclusion:

Based on the above findings, it can be concluded that present method is simple, precise, rapid, accurate and specific and thus, can be efficiently used for the pharmacokinetic study of metformin.

A HILIC-MS/MS assay for the quantification of metformin and sitagliptin in human plasma and urine: A tool for studying drug transporter perturbation

This article describes the development and validation of a HILIC-MS/MS method for the simultaneous quantification of metformin and sitagliptin from human plasma and urine. The presented method uses quick sample preparation and fast chromatography allowing for high sample throughput. The quantification is performed using multi-reaction monitoring and ESI positive mode with stable isotope labelled internal standards for both metformin and sitagliptin. Excellent linearity in the selected calibrations ranges, low inter-day variability (CV% <6.7%), and high accuracy (95.5-104.1%) were obtained. Adequate retention was attained for both analytes by hydrophilic interaction liquid chromatography using a plain silica column in combination with a mobile phase composed of ammonium formate, acetonitrile, formic acid and water in gradient separation mode.

Development and Validation of Liquid Chromatography Method for Determination of Glimepiride in Presence of (Vimto®) Soft Drinks in Rats: Application to Pharmacokinetics Studies

CONTEXT

Diet and beverages are thought to have notable effects on drugs. Recently, this relationship has received significant consideration.

AIMS

To develop and validate a simple, rapid, and sensitive method for the determination of glimepiride in rat serum. This will be performed using high-performance liquid chromatography-mass spectrometry (HPLC-MS/MS). Potential pharmacokinetic interactions between glimepiride and the soft drink, Vimto, will also be investigated in the serum of experimental rats.

MATERIALS AND METHODS

HPLC-MS/MS was constructed and clarithromycin was used as an internal standard.

RESULTS

The method was validated in terms of linearity, precision, accuracy, stability, and system suitability parameters. The method was found to be satisfactory and suitable for the determination of glimepiride. The precision of glimepiride was high (coefficient of variation, CV% <15%), the accuracy over all 3 days of validation was within the accepted criteria. Glimepiride peak serum concentration (C max) was 126.01 ng/mL and was reached within 1 h (T max) of administration. Mean area under curve (AUC) was 964.70 ng/mL and was reached within 24 h of administration. The Vimto soft drink significantly (P < 0.050) reduced glimepiride peak serum concentration to 57.87 ng/mL and was reached within 2 h of administration. AUC was significantly reduced to 335.04 ng*h/mL (P < 0.050).

CONCLUSION

Glimepiride pharmacokinetic parameters such as C max and AUC were significantly affected by the Vimto soft drink. Therefore, this study developed a simple, rapid, and sensitive method for validation and determination of the effects of soft drinks on drugs using the LC-MS/MS method.

The role of mass spectrometry in studies of glycation processes and diabetes management

In the last decade, mass spectrometry has been widely employed in the study of diabetes. This was mainly due to the development of new, highly sensitive, and specific methods representing powerful tools to go deep into the biochemical and pathogenetic processes typical of the disease. The aim of this review is to give a panorama of the scientifically valid results obtained in this contest. The recent studies on glycation processes, in particular those devoted to the mechanism of production and to the reactivity of advanced glycation end products (AGEs, AGE peptides, glyoxal, methylglyoxal, dicarbonyl compounds) allowed to obtain a different view on short and long term complications of diabetes. These results have been employed in the research of effective markers and mass spectrometry represented a precious tool allowing the monitoring of diabetic nephropathy, cardiovascular complications, and gestational diabetes. The same approaches have been employed to monitor the non-insulinic diabetes pharmacological treatments, as well as in the discovery and characterization of antidiabetic agents from natural products. © 2018 Wiley Periodicals, Inc. Mass Spec Rev 38:112-146, 2019.

High-Dose Metformin May Increase the Concentration of Atorvastatin in the Liver by Inhibition of Multidrug Resistance-Associated Protein 2

In this study, we evaluated the effect of coadministered metformin on the biliary excretion and liver concentration of atorvastatin. To investigate the inhibitory effect of metformin on biliary efflux transporters, the transport of atorvastatin in MDCKII-MDR1, BCRP, and MRP2 was evaluated. The effects of metformin on the steady state liver concentration and biliary excretion of atorvastatin and 2-hydroxyatorvastatin were evaluated in SDR and Mrp2-deficient EHBR. Metformin did not inhibit the transport of atorvastatin via BCRP and MDR1. However, metformin significantly inhibited the transport of atorvastatin and 2-hydroxyatorvastatin via MRP2 (apparent IC₅₀ = 12 and 2 μM). Coadministered metformin significantly increased the K_p,liver and C_liver (1.7- and 1.6-fold) and decreased the biliary clearance of atorvastatin (2.7-fold) in SDR, but it did not affect the plasma concentration and total clearance of atorvastatin. Similar effects by metformin were observed for 2-hydroxyatorvastatin. In addition, coadministered metformin did not have any effect in EHBR. Therefore, coadministered metformin increases the liver concentration of atorvastatin via inhibition of the Mrp2 in rats, without affecting the plasma concentration. This "silent interaction" by metformin in atorvastatin and metformin combination therapy may be related to the unnoticeable pharmacological synergism or unpredicted side effects of atorvastatin in the liver.

An integrated Taguchi and response surface methodological approach for the optimization of an HPLC method to determine glimepiride in a supersaturatable self-nanoemulsifying formulation

We studied the application of Taguchi orthogonal array (TOA) design during the development of an isocratic stability indicating HPLC method for glimepiride as per TOA design; twenty-seven experiments were conducted by varying six chromatographic factors. Percentage of organic phase was the most significant (p < 0.001) on retention time, while buffer pH had the most significant (p < 0.001) effect on tailing factor and theoretical plates. TOA design has shortcoming, which identifies the only linear effect, while ignoring the quadratic and interaction effects. Hence, a response surface model for each response was created including the linear, quadratic and interaction terms. The developed models for each response found to be well predictive bearing an acceptable adjusted correlation coefficient (0.9152 for retention time, 0.8985 for tailing factor and 0.8679 for theoretical plates). The models were found to be significant (p < 0.001) having a high F value for each response (15.76 for retention time, 13.12 for tailing factor and 9.99 for theoretical plates). The optimal chromatographic condition uses acetonitrile - potassium dihydrogen phosphate (pH 4.0; 30 mM) (50:50, v/v) as the mobile phase. The temperature, flow rate and injection volume were selected as 35 ± 2 °C, 1.0 mL min(-1) and 20 μL respectively. The method was validated as per ICH guidelines and was found to be specific for analyzing glimepiride from a novel supersaturatable self-nanoemulsifying formulation.

Development and Validation of an HPLC Method for Simultaneous Quantification of Clopidogrel Bisulfate, Its Carboxylic Acid Metabolite, and Atorvastatin in Human Plasma: Application to a Pharmacokinetic Study

A simple, sensitive, and specific reversed phase liquid chromatographic method was developed and validated for simultaneous quantification of clopidogrel, its carboxylic acid metabolite, and atorvastatin in human serum. Plasma samples were deproteinized with acetonitrile and ibuprofen was chosen as internal standard. Chromatographic separation was performed on an BDS Hypersil C18 column (250 × 4.6 mm; 5 μm) via gradient elution with mobile phase consisting of 10 mM phosphoric acid (sodium) buffer solution (pH = 2.6 adjusted with 85% orthophosphoric acid) : acetonitrile : methanol with flow rate of 1 mL·min(-1). Detection was achieved with PDA detector at 220 nm. The method was validated in terms of linearity, sensitivity, precision, accuracy, limit of quantification, and stability tests. Calibration curves of the analytes were found to be linear in the range of 0.008-2 μg·mL(-1) for clopidogrel, 0.01-4 μg·mL(-1) for its carboxylic acid metabolite, and 0.005-2.5 μg·mL(-1) for atorvastatin. The results of accuracy (as recovery) with ibuprofen as internal standard were in the range of 96-98% for clopidogrel, 94-98% for its carboxylic acid metabolite, and 90-99% for atorvastatin, respectively.

Stability Indicating RP-HPLC Method for the Simultaneous Determination of Atorvastatin Calcium, Metformin Hydrochloride, and Glimepiride in Bulk and Combined Tablet Dosage Form

A simple, rapid, and precise RP-HPLC method for simultaneous analysis of atorvastatin calcium, metformin hydrochloride, and glimepiride in bulk and its pharmaceutical formulations has been developed and validated. These drugs were separated by using Grace Smart Altima C-8 column (250 × 4.6 mm, 5-μm) with a mobile phase consisting of acetonitrile : phosphate buffer (60 : 40 (v/v), pH 3.0) at a flow rate of 1 mL/min, injection volume 25 µL, and detection at 235 nm. Metformin, atorvastatin, and glimepiride were eluted with retention times of 2.57 min, 7.06 min, and 9.39 min, respectively. The method was validated for accuracy, precision, linearity, specificity, and sensitivity in accordance with ICH (Q2B) guidelines. The results of all the validation parameters were found to be within the acceptable limits. The calibration plots were linear over the concentration ranges from 10 to 150 µg/mL, 20 to 200 µg/mL, and 10 to 150 µg/mL for atorvastatin, metformin, and glimepiride, respectively. The accuracy and precision were found to be between 98.2%-105% and ≤2% for three drugs. Developed method was successfully applied for the determination of the drugs in tablet dosage form and recovery was found to be >98% for three drugs. The degradation products produced as a result of stress studies did not interfere with drug peaks.

Pharmacokinetic study of inosiplex tablets in healthy Chinese volunteers by hyphenated HPLC and tandem MS techniques

Inosiplex is a compound formulation composed of inosine and p-acetaminobenzoic acid (PABA) salt of N,N-dimethylamino-2-propanol (DIP). This study was to investigate the clinical plasma pharmacokinetic properties of DIP and PABA after single and multiple oral doses of inosiplex tablets in healthy Chinese volunteers. The established LC/MS/MS method for plasma DIP determination had a linear range of 0.02–10 µg/mL, and the HPLC method for plasma PABA determination had a linear range of 0.05–40 µg/mL. Linear pharmacokinetic characteristics were found with single oral doses of 0.5, 1.0 and 2.0 g. No obvious accumulation effects were observed for DIP and PABA.

Performance evaluation of a novel potentiometric membrane sensor for determination of atorvastatin in pharmaceutical preparations

A novel potentiometric ion-selective PVC membrane sensor for analysis of atorvastatin (AT) in pharmaceutical preparations based on atorvastatin-(tetraphenyl borate), (AT-(TPB)2) as sensing element, tetraphenyl borate as additive and tris-2-ethyl-hexyl phosphate (TOP) as plasticizer solvent was prepared. The electrode shows a good Nernestian response over the concentration range of 0.09-5586 μg mL(-1)of AT with slope of 30.1±0.1 mV/decade and limit of detection0.056μg mL(-1).The response time of sensor is fats (less than 10 sec) and could be used for about one month in the pH range of 4.5-8.0. The electrode exhibit good selectivity for the AT in the presence of large amount of co-drugs and inorganic cations. The method is precise and accurate with mean relative standard deviation of <2%.Atorvastatin is determined successfully in several tablets by the proposed membrane.