Simultaneous determination of metformin and gliclazide in human plasma by liquid chromatography-tandem mass spectrometry: application to a bioequivalence study of two formulations in healthy volunteers

Metformin as an emerging concern in wastewater: Occurrence, analysis and treatment methods

Metformin is a wonder drug used as an anti-hypoglycemic medication; it is also used as a cancer suppression medicament. Metformin is a first line of drug choice used by doctors for patients with type 2 diabetes. It is used worldwide where the drug's application varies from an anti-hypoglycemic medication to cancer oppression and as a weight loss treatment drug. Due to its wide range of usage, metformin and its byproducts are found in waste water and receiving aquatic environment. This leads to the accumulation of metformin in living beings and the environment where excess concentration levels can lead to ailments such as lactic acidosis or vitamin B12 deficiency. This drug could become of future water treatment concerns with its tons of production per year and vast usage. As a result of continuous occurrence of metformin has demanded the need of implementing and adopting different strategies to save the aquatic systems and the exposure to metformin. This review discuss the various methods for the elimination of metformin from wastewater. Along with that, the properties, occurrence, and health and environmental impacts of metformin are addressed. The different analytical methods for the detection of metformin are also explained. The main findings are discussed with respect to the management of metformin as an emerging contaminants and the major recommendations are discussed to understand the major research gaps.

Simultaneous HPLC Assay of Gliclazide and Ciprofloxacin in Plasma and its Implementation for Pharmacokinetic Study in Rats

A simple and reliable high-performance liquid chromatography method for simultaneous quantitation of gliclazide and ciprofloxacin in plasma sample has been developed and validated. This method implements protein precipitation, a simple and practical pretreatment method by the addition of acetonitrile that gives a clean supernatant. The separation was carried out in a system consisted of a C18 column with acetonitrile and KH2PO4 (0.01 M, 0.1% v/v of triethylamine, pH 2.7) as the mobile phase in a gradient elution at a total flow-rate of 1 mL/min. Gliclazide and ciprofloxacin were quantitated using an ultraviolet detector set at wavelengths of 229 and 277 nm, respectively, which ensures optimal sensitivity for both compounds. This method possesses an excellent linearity at concentration ranges of 0.5-50 mg/L for gliclazide and 0.1-10 mg/L for ciprofloxacin. High within- and between-run accuracy for both gliclazide (% error of -8.00 to 0.45%) and ciprofloxacin (% error of -10.00 to 7.63%) were demonstrated. The intra- and inter-day precision (expressed as %CV) was <8 and 12% for gliclazide and ciprofloxacin, respectively. Both analytes were stable during storage and sample processing. The method reported in this study can be implemented for pharmacokinetic interaction study in rats.

Synthesis of sandwich-structured magnetic graphene-Zn-MOFs composites for quantitative determination of acarbose in rat plasma

In this study, sandwich-structured magnetic graphene composites with Zn metal-organic framework layer coated on both two sides (denoted as magG@Zn-MOFs) were synthesized. The composites have large specific surface of 114 m² g⁻¹, uniform porous structure and rapid magnetic separation within 10 s. The magG@Zn-MOFs composites were used for extraction of acarbose in plasma prior to its quantitative analysis by LC-MS/MS. The established method has good linearity (10-1000 ng mL^-1), satisfactory recovery (94.3-107.5%), low detection limit (as low as 2.5 ng mL^-1), good intra-day precision (RSD 3.5-5.3%) and inter-day precision (RSD 6.3-8.1%). Finally, the method was successfully applied to pharmacokinetic study of acarbose in rats.

Novel LC-MS/MS method for analysis of metformin and canagliflozin in human plasma: application to a pharmacokinetic study

Highly sensitive and selective liquid chromatography/tandem mass spectrometry (LC-MS/MS) method was developed and validated for the simultaneous estimation of the recently approved oral hypoglycemic mixture; metformin (MET) and canagliflozin (CFZ) in human plasma using propranolol HCl (PPL) and tadalafil (TDF) as internal standards (IS), respectively. Analytes were extracted using protein precipitation induced by acetonitrile then liquid-liquid extraction was performed using ethyl acetate. Reversed phase HPLC was carried out using C18 analytical column (50 mm × 4.6 mm i.d., 5 µm) with a simple isocratic mobile phase composed of 0.1% formic acid and acetonitrile (60:40, v/v). Detection was performed on a triple quadrupole mass spectrometer employing electrospray ionization technique, operating in multiple reaction monitoring (MRM), with the transitions of m/z 130.2 → 60.1, m/z 462.3 → 191.0, m/z 260.2 → 183.0 and m/z 390.2 → 268.2 for MET, CFZ, PPL and TDF, respectively, in the positive ion mode. The analysis was carried out within 5 min over a linear concentration range of 50-5000 ng/mL for MET and 10-1000 ng/mL for CFZ. The method was validated in accordance with the FDA guidelines for bioanalytical method. All obtained recoveries were higher than 90.0% while the accuracy was in the range of 88.14-113.05% and the relative standard deviation was below 10.0% for all investigated drugs by the proposed method. The achieved promising results has allowed for the successful application of the developed LC-MS/MS method to a pharmacokinetic study of the target drugs after their oral administration to Egyptian healthy volunteers. The pharmacokinetic study was accomplished after the agreement of the ethics committee.

Liquid chromatography tandem mass spectrometry for the simultaneous determination of metformin and pioglitazone in rat plasma: Application to pharmacokinetic and drug-drug interaction studies

Failure to attain and sustain long term glycemic control is an ongoing challenge in diabetes therapy. The trend to use a combined therapy and the risk of drug-drug interaction (DDI) are elevated and thus the need for sensitive analytical methods is of great significance. Herein, a simple, robust, and sensitive reverse phase high performance liquid chromatography-electrospray ionization-tandem mass spectrometry (ESI-MS/MS) method for simultaneous determination of metformin (MET) and pioglitazone (PGT) in rat plasma using canagliflozin (CAN) as internal standards (IS) was developed and fully validated. Prior Chromatographic separation on an Agilent Eclipse Plus C18 (4.6 × 100 mm, 3.5 μm) using gradient mobile phase system consisting of ammonium formate pH 4.5 and acetonitrile at a flow rate of 0.5 mL min^-1, within a run time of 14 min, the antidiabetic drugs were extracted from rat plasma using acetonitrile-induced protein precipitation technique. Multiple reaction monitoring in positive ion mode was used for quantitation of precursor to production at m/z 130.1 → 71.0 & 60 for MET, 357.2 → 134.2 for PGT, and 462.16 → 191.1 for CAN. Method linearity was obeyed in the range of 1 to 5000 and 1 to 2500 ng mL^-1 for MET and PGT, respectively. The developed method was validated in terms of accuracy, precision, selectivity, recovery, matrix effects, and stability as per US-FDA bioanalytical guidelines and successfully applied to clinical pharmacokinetic and DDI studies with a single oral administration of target compounds. The peak plasma concentrations (C_max) and area under the concentration-time curve (AUC) of MET was significantly influenced by the concomitant administration of PGT at equal concentration and vice versa. PGT affected the absorption and elimination rate of MET via inhibition of organic cationic transporter (OCT). Molecular modeling study revealed the significant interaction of PGT with OCT. A potential DDI in type 2 diabetic patient receiving chronic treatment with MET and PGT deserves further attention and study to improve drug therapy and prevent adverse effects.

Toxicological and Biochemical Analyses of an Autopsy Case Involving Oral Overdose of Multiple Antidiabetic and Antihypertensive Drugs

Oral antidiabetics can cause fatal hypoglycemia; although they can be chemically identified and quantified, biochemical investigations are important for assessing the biological consequences of an overdose. Such cases of overdose involving oral antidiabetics may involve other drugs for treating lifestyle-related diseases, particularly antihypertensives. Here, we report a toxicological and biochemical investigation of drugs and biochemical profiles in a fatal overdose involving multiple oral antidiabetics and antihypertensives. A 55-year-old woman died about 2 days after the ingestion of around 110 tablets of antidiabetics and antihypertensives that had been prescribed for her husband. A forensic autopsy and histological analysis demonstrated no evident pathology as the cause of death. A toxicological analysis suggested hypoglycemia and an overdose of antihypertensives as well as the retention of antidiabetics and diuretics in the pericardial fluid. A relatively low pericardial amlodipine concentration was observed, which may have been the result of its long half-life (slower distribution and reduction rate) and/or possible affinity with the myocardium. In addition, a biochemical analysis indicated hypoglycemia, without increased serum insulin and C-peptide, but with increased glucagon levels, as the possible influence of glibenclamide overdose. These observations suggest the usefulness of a combination of toxicological and biochemical analyses in postmortem investigations involving a fatal overdose of such drugs.

Hydrophilic Interaction Liquid Chromatography-Electrospray Ionization Mass Spectrometry for Therapeutic Drug Monitoring of Metformin and Rosuvastatin in Human Plasma

In this work a hydrophilic interaction liquid chromatography/positive ion electrospray mass spectrometric assay (HILIC/ESI-MS) has been developed and fully validated for the quantitation of metformin and rosuvastatin in human plasma. Sample preparation involved the use of 100 μL of human plasma, following protein precipitation and filtration. Metformin, rosuvastatin and 4-[2-(propylamino) ethyl] indoline 2 one hydrochloride (internal standard) were separated by using an X-Bridge-HILIC BEH analytical column (150.0 × 2.1 mm i.d., particle size 3.5 μm) with isocratic elution. A mobile phase consisting of 12% (v/v) 15 mM ammonium formate water solution in acetonitrile was used for the separation and pumped at a flow rate of 0.25 mL min⁻¹. The linear range of the assay was 100 to 5000 ng mL⁻¹ and 2 to 100 ng mL⁻¹ for metformin and rosuvastatin, respectively. The current HILIC-ESI/MS method allows for the accurate and precise quantitation of metformin and rosuvastatin in human plasma with a simple sample preparation and a short a chromatographic run time (less than 15 min). Plasma samples from eight patients were further analysed proving the capability of the proposed method to support a wide range of clinical studies.

Silica-coated magnetic iron oxide functionalized with hydrophobic polymeric ionic liquid: a promising nanoscale sorbent for simultaneous extraction of antidiabetic drugs from human plasma prior to their quantitation by HPLC

Herein, silica-coated iron oxide nanoparticles modified with imidazolium-based polymeric ionic liquid (Fe₃O₄@SiO₂@PIL) were fabricated as a sustainable sorbent for magnetic solid-phase extraction (MSPE) and simultaneous determination of trace antidiabetic drugs in human plasma by high-performance liquid chromatography-ultraviolet detection (HPLC-UV). The Fe₃O₄ core was functionalized by silica (SiO₂) and vinyl layers where the ionic liquid 1-vinyl-3-octylimidazolium bromide (VOIM-Br) was attached through a free radical copolymerization process. In order to achieve hydrophobic magnetic nanoparticles and increase the merits of the sorbent, Br⁻ anions were synthetically replaced with PF₆⁻. The properties and morphology of the sorbent were characterized by various techniques and all the results illustrated the prosperous synthesis of Fe₃O₄@SiO₂@PIL. A comprehensive study was carried out to investigate and optimize various parameters affecting the extraction efficiency. The limit of detection (LOD, S/N = 3) for empagliflozin, metformin and canagliflozin was 1.3, 6.0 and 0.8 ng mL⁻¹, respectively. Linearity (0.997 ≥ r² ≥ 0.993) and linear concentration ranges of 5.0–1200.0, 20.0–1800.0 and 5.0–1000.0 ng mL⁻¹ were obtained for empagliflozin, metformin and canagliflozin, respectively. Intra-assay (3.8–7.5%, n = 9) and inter-assay (3.2–8.5%, n = 12) precisions as well as accuracies (≤9.1%) displayed good efficiency of the method. Finally, the method was applied for the quantitation of antidiabetic drugs in human plasma after oral administration and main pharmacokinetic data including T_max (h), C_max (ng mL⁻¹), AUC_0–24 (ng h mL⁻¹), AUC_0–∞ (ng h mL⁻¹), and T_1/2 (h) were evaluated.

A sustainable nanoscale core–shell modified with hydrophobic polymeric ionic liquid was fabricated for simultaneous extraction and determination of antidiabetic drugs.

Bioanalytical methods for the detection of antidiabetic drugs: a review

Type 2 diabetes mellitus, a disease which prevalence has been progressively increasing worldwide, is characterized by chronic hyperglycemia resulting from the combination of inappropriate insulin secretion and/or resistance to insulin action. If left uncontrolled, diabetes is associated with complications such as dysfunction and failure of various organs, and even premature death. Along with lifestyle-modification strategies, several classes of oral antidiabetic agents can be employed for glycemic control. Thus, therapeutic drug monitoring of these drugs is essential to maintain appropriate treatment. This review discusses the most frequently employed analytical techniques and sample preparation systems to obtain a reliable and trustworthy method to quantify antidiabetic drugs in biological matrices. An adequate choice of internal standard, ideal chromatography conditions and most suitable analytical detector are reported.

Simultaneous Quantification of Antidiabetic Agents in Human Plasma by a UPLC-QToF-MS Method

An ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry method for the simultaneous quantification of chlorpropamide, glibenclamide, gliclazide, glimepiride, metformin, nateglinide, pioglitazone, rosiglitazone, and vildagliptin in human plasma was developed and validated, using isoniazid and sulfaquinoxaline as internal standards. Following plasma protein precipitation using acetonitrile with 1% formic acid, chromatographic separation was performed on a cyano column using gradient elution with water and acetonitrile, both containing 0.1% formic acid. Detection was performed in a quadrupole time-of-flight analyzer, using electrospray ionization operated in the positive mode. Data from validation studies demonstrated that the new method is highly sensitive, selective, precise (RSD < 10%), accurate (RE < 12%), linear (r > 0.99), free of matrix and has no residual effects. The developed method was successfully applied to volunteers' plasma samples. Hence, this method was demonstrated to be appropriate for clinical monitoring of antidiabetic agents.

LC-MS/MS analysis of metformin, saxagliptin and 5-hydroxy saxagliptin in human plasma and its pharmacokinetic study with a fixed-dose formulation in healthy Indian subjects

A specific and rapid liquid chromatography-tandem mass spectrometry method is proposed for the simultaneous determination of metformin (MET), saxagliptin (SAXA) and its active metabolite, 5-hydroxy saxagliptin (5-OH SAXA) in human plasma. Sample preparation was accomplished from 50 μL plasma sample by solid-phase extraction using sodium dodecyl sulfate as an ion-pair reagent. Reversed-phase chromatographic resolution of analytes was possible within 3.5 min on ACE 5CN (150 × 4.6 mm, 5 μm) column using acetonitrile and10.0 mm ammonium formate buffer, pH 5.0 (80:20, v/v) as the mobile phase. Triple quadrupole mass spectrometric detection was performed using electrospray ionization in the positive ionization mode. The calibration curves showed good linearity (r²  ≥ 0.9992) over the established concentration range with limit of quantification of 1.50, 0.10 and 0.20 ng/mL for MET, SAXA and 5-OH SAXA respectively. The extraction recoveries obtained from spiked plasma samples were highly consistent for MET (75.12-77.84%), SAXA (85.90-87.84%) and 5-OH SAXA (80.32-82.69%) across quality controls. The validated method was successfully applied to a bioequivalence study with a fixed-dose formulation consisting of 5 mg SAXA and 500 mg MET in 18 healthy subjects. The reproducibility of the assay was demonstrated by reanalysis of 87 incurred samples.

LC-tandem mass spectrometry method for the simultaneous determination of metformin and sitagliptin in human plasma after ion-pair solid phase extraction

A reversed-phase liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) method was established for simultaneous determination of two oral hypoglycemic drugs metformin (MET) and sitagliptin (STG) in human plasma. The analytes were extracted from 50μL human plasma by ion-pair solid phase extraction using sodium lauryl sulphate on Phenomenex Strata-X (30mg/1mL) cartridges. The chromatographic separation was accomplished on XSelect HSS CN (150×4.6mm, 5μm) column using mobile phase consisting of methanol-8.0mM ammonium formate in water, pH 4.5 (80:20, v/v) under isocratic condition. Tandem MS detection was performed on a triple quadrupole spectrometer equipped with an electrospray ionization source, operated in the positive mode. Multiple reaction monitoring (MRM) was used to quantify the analytes following transitions, m/z 130.1→60.1 and m/z 408.3→235.1 for MET and STG respectively. The method displayed acceptable linearity in the concentration range of 4.00-3200ng/mL for MET and 1.00-800ng/mL for STG. The intra-batch and inter-batch precisions were ≤5.1% and accuracy ranged from 96.5 to 103.3% for both the drugs. The mean recovery of MET and STG obtained from spiked plasma samples was 82.5% and 90.4% respectively with minimal matrix interference. Both the drugs were found to be stable under all mandatory storage conditions. The validated method was successfully applied to a clinical pharmacokinetic study for a fixed-dose tablet formulation containing 500mg MET and 50mg STG in 16 healthy volunteers.

Hydrophilic interaction chromatography-tandem mass spectrometry based on an amide column for the high-throughput quantification of metformin in rat plasma

A simple, highly sensitive, specific, reproducible, and high-throughput Amide-HILIC-MS/MS assay to quantify metformin in rat plasma was established and successfully applied for sample analysis to support pharmacokinetic studies.

Simultaneous identification, confirmation and quantitation of illegal adulterated antidiabetics in herbal medicines and dietary supplements using high-resolution benchtop quadrupole-Orbitrap mass spectrometry

This paper presents an application of ultrahigh-performance liquid chromatography and quadrupole Orbitrap high-resolution mass spectrometry (UHPLC-Q-Orbitrap HR MS) for the screening, confirmation and quantification of 11 antidiabetics in herbal medicines and dietary supplements. The mass spectrometer was operated in Full MS/dd-MS(2) (data-dependent MS(2)) mode. The full MS scan acquired data for identification and quantification, and dd-MS(2) scan obtained product ion spectra for confirmation. UHPLC-Q-Orbitrap MS quantification was achieved using matrix-matched standard calibration curves with phenacetin as internal standard. The method validation that included selectivity, sensitivity, calibration curve, accuracy and precision, recovery, matrix effect and stability was evaluated. The response showed good linear relationship with the concentrations of analytes over wide ranges (e.g., 0.0004-1 μg/g for metformin) with all the coefficients of correlation (r(2)) >0.9991. The detection limits (LODs) were in the range of 0.05-0.5 ng/g for different analytes. The recoveries yielded results higher than 74.3% for all compounds. The accuracy was in the range of -6.75 to 3.85%, while the intra- and inter-day precision ranged from 0.048 to 11.5%. Among 63 batches of herbal medicines and 34 batches of dietary supplements samples, 7 batches of dietary supplements were positive, while all the herbal medicines were negative. Overall, the novel UHPLC-Q-Orbitrap has demonstrated great performance for identification, confirmation and quantification of antidiabetics in herbal medicines and dietary supplements, ensuring food safety and public health.

Supramolecular Interaction of Gliclazide with Cucurbit[7]uril and its Analytical Application

Gliclazide (GLZ) is non-fluorescent in aqueous solution. This property makes its determination through direct fluorescent methods impossible. Palmatine (PAL) exhibits very weak fluorescence emissions in aqueous solution. However, in acidic media at room temperature, PAL can react with cucurbit[7]uril (CB[7]) to form a stable complex and the fluorescence intensity of the complex is greatly enhanced. Dramatic quenching of the fluorescence intensity of the CB[7]–PAL complex was observed with the addition of GLZ. The competing reactions and the supramolecular interaction mechanisms between GLZ and PAL as they fight for occupancy of the CB[7] cavity were studied using spectrofluorimetry, 1H NMR spectroscopy, and molecular modelling calculations. The association constants of the complexes formed between the host and the guest were determined. Based on the significant quenching of the supramolecular complex fluorescence intensity, a fluorescent probe method of high sensitivity was developed to determine GLZ in its pharmaceutical dosage forms and in human plasma with good precision and accuracy. The linear range of the method was from 0.003 to 2.100 μg mL–1. The limit of detection was 0.001 μg mL–1. This shows that the proposed method has promising potential for therapeutic monitoring and pharmacokinetics and for clinical application.

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

A simple, rapid and sensitive liquid chromatography-tandem mass spectrometric (LC–MS/MS) assay method has been developed and fully validated for the simultaneous quantification of atorvastatin, metformin and glimepiride in human plasma. Carbamazepine was used as internal standard (IS). The analytes were extracted from 200 μL aliquots of human plasma via protein precipitation using acetonitrile. The reconstituted samples were chromatographed on a Alltima HP C18 column by using a 60:40 (v/v) mixture of acetonitrile and 10 mM ammonium acetate (pH 3.0) as the mobile phase at a flow rate of 1.1 mL/min. The calibration curves obtained were linear (r²≥0.99) over the concentration range of 0.50–150.03 ng/mL for atorvastatin, 12.14–1207.50 ng/mL for metformin and 4.98–494.29 ng/mL for glimepiride. The API-4000 LC–MS/MS in multiple reaction monitoring (MRM) mode was used for detection. The results of the intra- and inter-day precision and accuracy studies were well within the acceptable limits. All the analytes were found to be stable in a battery of stability studies. The method is precise and sensitive enough for its intended purpose. A run time of 2.5 min for each sample made it possible to analyze more than 300 plasma samples per day. The developed assay method was successfully applied to a pharmacokinetic study in human male volunteers.

A supercritical fluid chromatography/tandem mass spectrometry method for the simultaneous quantification of metformin and gliclazide in human plasma

Present study reports the development and validation of a simultaneous estimation of metformin and gliclazide in human plasma using supercritical fluid chromatography followed by tandem mass spectrometry. Acetonitrile:water (80:20) mixture was used as a mobile phase along with liquid CO₂ in supercritical fluid chromatography and phenformin as an internal standard. The modified plasma samples were analyzed by electro-spray ionization method in selective reaction monitoring mode in tandem mass spectrometry. Supercritical fluid chromatographic separation was performed using nucleosil C₁₈ containing column as a stationary phase. The separated products were identified by characteristic peaks and specific fragments peaks in tandem mass spectrometry as m/z 130 to 86 for metformin, m/z 324 to 110 for gliclazide and m/z 206 to 105 for phenformin. The present method was found linear in the concentration ranges of 6.0-3550 ng/ml and 7.5-7500 ng/ml for metformin and gliclazide, respectively. Pharmacokinetic study was performed after an oral administration of dispersible tablets containing 500 mg of metformin and 80 mg of gliclazide using same techniques.

Trace analysis of glyclazide in human plasma at microscale level by mass spectrometry

Green (reagents and organic solvents saving) analytical chemistry is a new strategy for pharmaceutical analysis. The principles of this idea include primary elimination or at least reduction of the amounts of organic reagents and solvents. In this study, we have provided two simple methods for the analysis of clinical drugs in human plasma. One is the capillary LC (Cap LC) connected to MS-MS, the other is the matrix-assisted laser desorption ionization (MALDI) connected to TOF MS. Sulfonylurea drugs are usually used in diabetes mellitus patients. Diabetes is a syndrome of disordered metabolism resulting in abnormally high blood sugar levels (hyperglycemia). These microscale methods were successfully applied for the monitoring of drug levels in human plasma using gliclazide (a second-generation sulfonylurea) as the test platform. The sensitivity of these methods is sufficient for detecting the gliclazide within a therapeutic range. All the analytical procedures (including human plasma, sample preparation, and flow rate of the analytical system) were at microscale level. These two methods would lower the consumption of organic solvents further safeguarding our environment.

Liquid chromatography tandem mass spectrometry method for simultaneous determination of antidiabetic drugs metformin and glyburide in human plasma

A simple and rapid liquid chromatography/tandem mass spectrometry (LC-MS/MS) method has been developed and validated for the simultaneous quantitation of antidiabetic drugs metformin and glyburide in human plasma using glimepiride as internal standard (IS). After acidic acetonitrile-induced protein precipitation of the plasma samples, metformin, glyburide and IS were chromatographed on reverse phase C18 (50 mm x 4.6 mm i.d., 5 microm) analytical column. Quantitation was performed on a triple quadrupole mass spectrometer employing electrospray ionization technique and operating in multiple reaction monitoring (MRM) and positive ion mode. The total chromatographic run time was 3.5 min and calibration curves were linear over the concentration range of 20-2500 ng/ml for metformin and 5-500 ng/ml for glyburide. The method was validated for selectivity, sensitivity, recovery, linearity, accuracy and precision, dilution integrity and stability studies. The recoveries obtained for the analytes and IS (>or=69%) were consistent and reproducible. Inter-batch and intra-batch coefficient of variation across four validation runs (LLOQ, LQC, MQC and HQC) was less than 8%. The accuracy determined at these levels was within +/-8% in terms of relative error (RE). The method was applied to a bioequivalence study of 500 mg metformin and 5mg of glyburide tablet after oral administration to 28 healthy human subjects under condition of fasting.

Multi-component plasma quantitation of anti-hyperglycemic pharmaceutical compounds using liquid chromatography-tandem mass spectrometry

Type-2 diabetes is a disorder characterized by disrupted insulin production leading to high blood glucose levels. To control this disease, combination therapy is often used. Hypoglycemic agents such as metformin, glipizide, glyburide, repaglinide, rosiglitazone, nateglinide, and pioglitazone are widely prescribed to control blood sugar levels. These drugs provide the basis for the development of a quantitative multianalyte bioanalytical method. As an example, a highly sensitive and selective multi-drug method based on liquid chromatography tandem mass spectrometry (LC-MS/MS) was developed. This rapid, automated method consists of protein precipitation of 20 microL of plasma coupled with gradient HPLC elution of compounds using 10 mM ammonium formate buffer and 0.1% formic acid in acetonitrile as the mobile phases. MS/MS detection was performed using turbo ion spray in the positive ion multiple reaction monitoring (SRM) mode. A lower limit of quantitation (LLQ) in a range of 1.0-5.0 ng/mL was achieved for all analytes. The linearity of the method was observed over a 500-fold dynamic range. Drug recoveries ranged from 86.2 to 94.2% for all analytes of interest. Selectivity, sample dilution, intra-day and inter-day accuracy and precision, and stability assessment were evaluated for all compounds.

Simultaneous determination of metformin and rosiglitazone in human plasma by liquid chromatography/tandem mass spectrometry with electrospray ionization: application to a pharmacokinetic study

A selective and sensitive high performance liquid chromatography-electrospray ionization-tandem mass spectrometry (ESI-MS/MS) method for simultaneous determination of metformin and rosiglitazone in human plasma using phenformin as internal standard (IS) has been first developed and validated. Plasma samples were precipitated by acetonitrile and the analytes were separated on a prepacked Phenomenex Luna 5u CN 100A (150 mm x 2.0 mm I.D.) column using a mobile phase comprised of methanol:30 mM ammonium acetate pH 5.0 (80:20, v/v) delivered at 0.2 ml/min. Detection was performed on a Finnigan TSQ triple-quadrupole tandem mass spectrometer in positive ion selected reaction monitoring (SRM) mode using electrospray ionization. The ion transitions monitored were m/z 130.27-->71.11 for metformin, m/z 358.14-->135.07 for rosiglitazone and m/z 206.20-->105.19 for the IS. The standard curves were linear (r(2)>0.99) over the concentration range of 5-3000 ng/ml for metformin and 1.5-500 ng/ml for rosiglitazone with acceptable accuracy and precision, respectively. The within- and between-batch precisions were less than 15% of the relative standard deviation. The limit of detection (LOD) of both metformin and rosiglitazone was 1 ng/ml. The method described is precise and sensitive and has been successfully applied to the study of pharmacokinetics of compound metformin and rosiglitazone capsules in 12 healthy Chinese volunteers.