Quantitation of Metformin in Human Plasma and Urine by Hydrophilic Interaction Liquid Chromatography and Application to a Pharmacokinetic Study

Using a limited sampling strategy to investigate the interindividual pharmacokinetic variability in metformin: A large prospective trial

AIMS

Recently a limited sampling strategy (LSS) for determination of metformin' pharmacokinetics was developed. The LSS utilizes the plasma concentration of metformin 3 and 10 hours after oral intake of a single dose to estimate the area under the concentration-time curve up to 24 hours (AUC_0-24h ). The main purpose of this study was to support the feasibility of this strategy in a large prospective trial.

METHODS

Volunteers orally ingested two 500-mg tablets of metformin hydrochloride. A blood sample was drawn three and ten hours after the ingestion. Urine was collected for 0-10 and 10-24 hours and urine volumes recorded. The AUC_0-24h was calculated using the equation AUC_0-24h = 4.779 * C₃ + 13.174 * C₁₀ . Additionally, all participants were genotyped for the single-nucleotide polymorphism A270S in OCT2, g.-66 T > C in MATE1, R61C, G465R, G401S and the deletion M420del in OCT1.

RESULTS

In total, 212 healthy volunteers participated. The median (25th - 75th interquartile range) AUC_{0 - 24h} , CL_renal , C₃ and C₁₀ , were 10 600 (8470-12 500) ng* hr* mL^-1 , 29 (24-34) L* hour^-1 , 1460 (1180-1770) and 260 (200-330) ng* mL^-1 , respectively, which is in agreement with our previous results. GFR_i was correlated with metformin AUC and CL_renal (P < .001). As expected, we found a great pharmacokinetic interindividual variability among the volunteers and no effect of the OCT1 genotype on the AUC_{0 - 24h} . We were unable to reproduce our previous finding of a gene-gene interaction (OCT2 and MATE1) effect on CL_renal in this cohort.

CONCLUSION

This study further supports the use of the 2-point LSS algorithm in large pharmacokinetic trials.

Metformin Biodistribution: A Key to Mechanisms of Action?

Metformin has undisputed glucose-lowering effects in diabetes and an impressive safety record. It has also shown promising effects beyond diabetes, and several hundred clinical trials involving metformin are currently planned or active. Metformin targets intracellular effectors, but exactly which remain to be established, and in an era of precision medicine, an incomplete understanding of mechanisms of action may limit the use of metformin. Distribution of metformin depends on specific organic cation transporter proteins that are organ- and species-specific. Therefore, target tissues of metformin can be identified by cellular uptake of the drug, and exploring the biodistribution of the drug in humans becomes an attractive strategy to assist the many investigations into the mechanisms of action of metformin performed in animals. In this review, we combine the emerging evidence from the use of 11C-labeled metformin in humans to discuss metformin action in liver, intestines, and kidney, which are the organs with the most avid uptake of the drug.

Design of a cluster-randomized trial of the effectiveness and cost-effectiveness of metformin on prevention of type 2 diabetes among prediabetic Mexican adults (the PRuDENTE initiative of Mexico City)

INTRODUCTION

Type 2 diabetes (T2D) is a global epidemic, and nations are struggling to implement effective healthcare strategies to reduce the burden. While efficacy studies demonstrate that metformin can reduce incident T2D by half among younger, obese adults with prediabetes, its real-world effectiveness are understudied, and its use for T2D prevention in primary care is low. We describe the design of a pragmatic trial to evaluate the incremental effectiveness of metformin, as an adjunct to a simple lifestyle counseling.

METHODS

The "Prevención de la Diabetes con Ejercicio, Nutrición y Tratamiento" [Diabetes Prevention with Exercise, Nutrition and Treatment; PRuDENTE, (Spanish acronym)] is a cluster-randomized trial in Mexico City's public primary healthcare system. The study randomly assigns 51 clinics to deliver one of two interventions for 36 months: 1) lifestyle only; 2) lifestyle plus metformin, to 3060 patients ages 30-65 with impaired fasting glucose and obesity. The primary endpoint is incident T2D (fasting glucose ≥126 mg/dL, or HbA1c ≥6.5%). We will also measure a range of implementation-related process outcomes at the clinic-, clinician- and patient-levels to inform interpretations of effectiveness and enable efforts to refine, adapt, adopt and disseminate the model. We will also estimate the cost-effectiveness of metformin as an adjunct to lifestyle counseling in Mexico.

DISCUSSION

Findings from this pragmatic trial will generate new translational knowledge in Mexico and beyond, both with respect to metformin's real-world effectiveness among an 'at-risk' population, and uncovering facilitators and barriers to the reach, adoption and implementation of metformin preventive therapy in public primary care settings.

TRIAL REGISTRATION

This trial is registered at Clinicaltrials.gov (NCT03194009).

Electrochemically Modulated Liquid-Liquid Extraction for Sample Enrichment

A new sample preparation method is proposed for the extraction of pharmaceutical compounds (Metformin, Phenyl biguanide, and Phenformin) of varied hydrophilicity, dissolved in an aqueous sample. When in contact with an organic phase, an interfacial potential is imposed by the presence of an ion, tetramethylammonium (TMA⁺), common to each phase. The interfacial potential difference drives the transfer of ionic analytes across the interface and allows it to reach up to nearly 100% extraction efficiency and a 60-fold enrichment factor in optimized extraction conditions as determined by HPLC analysis.

PRE-surgical Metformin In Uterine Malignancy (PREMIUM): a Multi-Center, Randomized Double-Blind, Placebo-Controlled Phase III Trial

PURPOSE

Endometrioid endometrial cancer is strongly associated with obesity and insulin resistance. Metformin, an insulin sensitizer, reduces endometrial tumor growth in vitro. Presurgical window studies allow rapid in vivo assessment of antitumor activity. Previous window studies found metformin reduced endometrial cancer proliferation but these lacked methodological rigor. PREMIUM measured the anti-proliferative effect of metformin in vivo using a robust window study design.Patients and Methods: A multicenter, double-blind, placebo-controlled trial randomized women with atypical hyperplasia or endometrioid endometrial cancer to receive metformin (850 mg daily for 3 days, and twice daily thereafter) or placebo for 1 to 5 weeks until surgery. The primary outcome was posttreatment IHC expression of Ki-67. Secondary outcomes investigated the effect of metformin on markers of the PI3K-Akt-mTOR and insulin signaling pathways and obesity.

RESULTS

Eighty-eight women received metformin (n = 45) or placebo (n = 43) and completed treatment. There was no overall difference in posttreatment Ki-67 between the metformin and placebo arms, in an ANCOVA analysis adjusting for baseline Ki-67 expression (mean difference -0.57%; 95% CI, -7.57%-6.42%; P = 0.87). Metformin did not affect expression of markers of the PI3K-Akt-mTOR or insulin signaling pathways, and did not result in weight loss.

CONCLUSIONS

Short-term treatment with standard diabetic doses of metformin does not reduce tumor proliferation in women with endometrioid endometrial cancer awaiting hysterectomy. This study does not support a biological effect of metformin in endometrial cancer and casts doubt on its potential application in the primary and adjuvant treatment settings.

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.

Mechanistic study for the simultaneous determination of metformin and teneligliptin in human plasma using hydrophilic interaction liquid chromatography–MS/MS

Aim: A simple, selective and sensitive hydrophilic interaction liquid chromatography-MS/MS method is developed for the simultaneous determination of metformin (MET) and teneligliptin (TEN) in human plasma using deuterated internal standards. The mechanism of retention of analytes was studied by varying the proportion of organic diluent, buffer strength, pH of the mobile phase and temperature. Results: The results showed a mixed-mode mechanism comprising of hydrophilic (partition) and electrostatic interaction (ion exchange) for MET and essentially hydrophilic for TEN. The linear calibration curves were established in the concentration range of 1.0–1000 ng/ml for MET and 0.50–750 ng/ml for TEN. Conclusion: The method was applied to determine plasma concentration of MET and TEN in healthy subjects.

METFORMIN: NONGLYCEMIC EFFECTS AND POTENTIAL NOVEL INDICATIONS

OBJECTIVE

Metformin is the most commonly prescribed drug for the treatment of type 2 diabetes because of its apparent robust effects in reducing cardiovascular risk. This review examines the current literature regarding the nonglycemic effects and potential novel indications for metformin.

METHODS

Review of the literature, with a focus on metformin use in Stage 3 chronic kidney disease (CKD-3) and heart failure (HF).

RESULTS

The United Kingdom Prospective Diabetes Study suggests that metformin reduces the risk of myocardial infarction, and more recent retrospective studies have shown an association between metformin use and a reduction in stroke, atrial fibrillation and all-cause mortality. The mechanism(s) explaining these putative benefits are not clear but may involve decreased energy intake (with attendant weight loss), improvement in lipids, and lowering of blood pressure; a literature review suggests that metformin lowers blood pressure when it is elevated, but not when it is normal. Metformin appears to be safe when given to patients with CKD-3. In addition, there is evidence that individuals with CKD-3, who are at increased cardiovascular risk, stand to benefit from metformin therapy. Lactic acidosis is an extremely remote and probably avoidable risk; measurement of plasma metformin levels and more frequent monitoring of renal function may be useful in selected patients with CKD-3 who are treated with metformin. Finally, there is evidence that metformin is safe in patients with HF; metformin therapy is associated with a reduction in newly incident HF and in HF mortality.

CONCLUSION

Metformin has a dominant position in the treatment of type 2 diabetes that is deserved due to its favorable and robust effects on cardiovascular risk.

ABBREVIATIONS

AMP = adenosine monophosphate BP = blood pressure CKD = chronic kidney disease CKD-3 = Stage 3 CKD eGFR = estimated glomerular filtration rate HDL = high-density lipoprotein HF = heart failure MAP = mean arterial pressure mVO2 = myocardial oxygen consumption T2DM = type 2 diabetes mellitus UKPDS = United Kingdom Prospective Diabetes Study.

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.

A twin study of the trough plasma steady-state concentration of metformin

OBJECTIVE

The aim of this study was to determine the intrapair similarity in trough steady-state plasma concentrations of metformin in monozygotic and dizygotic twin pairs.

METHODS

We included 16 twin pairs (eight monozygotic and eight dizygotic twin pairs) for this study after contacting 524 twin pairs. They were dosed with metformin to steady state (1 g twice daily) for 6 days and on day 7, the trough concentration of metformin was determined 12 h after the last dose.

RESULTS

There was no strong intrapair similarity in trough steady-state plasma concentrations of metformin in either dizygotic or monozygotic twin pairs.

CONCLUSION

The trough steady-state plasma concentration of metformin does not appear to be tightly genetically regulated. The interpretation of this finding is limited by the small sample size.

Intake of St John's wort improves the glucose tolerance in healthy subjects who ingest metformin compared with metformin alone

AIMS

Our objective was to investigate the steady-state pharmacokinetic and pharmacodynamic interaction between the antidepressive herbal medicine St John's wort and the antidiabetic drug metformin.

METHODS

We performed an open cross-over study in 20 healthy male subjects, who received 1 g of metformin twice daily for 1 week with and without 21 days of preceding and concomitant treatment with St John's wort. The pharmacokinetics of metformin was determined, and a 2 h oral glucose tolerance test was performed.

RESULTS

St John's wort decreased the renal clearance of metformin but did not affect any other metformin pharmacokinetic parameter. The addition of St John's wort decreased the area under the glucose concentration-time curve [702 (95% confidence interval, 643-761) vs. 629 min*mmol/L (95% confidence interval, 568-690), P = 0.003], and this effect was caused by a statistically significant increase in the acute insulin response.

CONCLUSIONS

St John's wort improves glucose tolerance by enhancing insulin secretion independently of insulin sensitivity in healthy male subjects taking metformin.

Steady-state pharmacokinetics of metformin is independent of the OCT1 genotype in healthy volunteers

PURPOSE

The aim of the study was to determine the steady-state pharmacokinetics of metformin in healthy volunteers with different numbers of reduced-function alleles in the organic cation transporter 1 gene (OCT1).

METHODS

The study was conducted as part of a randomized cross-over trial. Thirty-four healthy volunteers with known OCT1 genotypes (12 with two wild-type alleles, 13 with one and 9 with two reduced-function alleles) were included. In one of the study periods, they were titrated to steady-state with 1 g metformin twice daily.

RESULTS

Neither AUC(0-12), C(max) nor Cl(renal) were statistically significantly affected by the number of reduced-function alleles (0, 1 or 2) in OCT1: (AUC(0-12): 0, 1, 2: 14, 13 and 14 h ng/L (P = 0.61)); (C(max): 0, 1, 2: 2192, 1934 and 2233 ng/mL, (P = 0.26)) and (Cl(renal): 0, 1, 2: 31, 28 and 30 L/h (P = 0.57)) CONCLUSIONS: In a cohort of healthy volunteers, we found no impact of different OCT1 genotypes on metformin steady-state pharmacokinetics.

Recent advances in hydrophilic interaction chromatography for quantitative analysis of endogenous and pharmaceutical compounds in plasma samples

There is an increasing need for new analytical methods that can handle a large number of analytes in complex matrices. Hydrophilic interaction chromatography (HILIC) has recently been demonstrated as an important supplement to reversed-phase liquid chromatography for polar analytes, particularly endogenous compounds. With the increasing popularity of HILIC, progressively more polar phases with diverse functional groups have been developed. In addition, the coupling of HILIC to mass spectrometry offers the advantages of improved sensitivity by employing an organic-rich mobile phase. This article reviews recent applications of HILIC for the analysis of endogenous and pharmaceutical compounds in plasma samples. Furthermore, based on recent studies, we provide a discussion of column selection, sample pretreatment for HILIC analysis, and detection sensitivity.