A validated method for the determination of verapamil and norverapamil in human plasma

Enhancing verapamil trace determination from biological matrices by bar adsorptive microextraction

Verapamil is an L-type calcium channel blocker widely used in the treatment of cardiovascular diseases such as hypertension, angina and arrhythmias, requiring accurate therapeutic monitoring to maintain plasma, urine and saliva concentrations within a safe range. In this context, a novel analytical approach has been proposed to determine verapamil in biological samples, using bar adsorptive microextraction coated with reversed-phase polymers followed by high-performance liquid chromatography with diode array detection. Two adsorbents have been chosen, i.e. STRATA-CN and ENVI-18 polymers, showing recoveries from 56.01 ± 2.16% to 96.82 ± 0.61% under optimized experimental conditions, such as sample pH: 10.0 (STRATA-CN) and 8.0 (ENVI-18), 2 h of equilibrium time, stirring speed at 990 rpm, back-extraction solvent using methanol:acetonitrile (1 : 1 v/v), and 1 h under sonication. The analytical method showed linearity from 20 to 600 ng mL-1 (r ≥ 0.99), as well as adequate precision (with RSD% below 15%) and accuracy (with RE% within 15% of the nominal value). Finally, the analytical method was applied to plasma, urine and saliva samples and proved to be a promising alternative for the trace analysis of verapamil in biological matrices.

Analytical techniques for the determination of verapamil in biological samples and dosage forms: an overview

Verapamil (VER) is a calcium channel blocker that is widely used to treat various cardiovascular diseases and is also effective in migraine prophylaxis. As the therapeutic range of VER is very narrow and toxicity can occur in patients after oral administration, therapeutic drug monitoring is recommended to optimize pharmacotherapy. The choice of an appropriate bioanalytical method for therapeutic drug monitoring of VER in the biological samples is a very important step in achieving fast and reliable results. This review focuses on the various analytical methods reported between 1976 and 2019 for the determination of VER in different biological samples and pharmaceutical dosage forms along with their methodological limitations. This review provides an overview for pharmaceutical industry researchers, clinicians and clinical chemists.

Determination of Verapamil in Exhaled Breath Condensate by Using Microextraction and Liquid Chromatography

Background:

Developing a simple analysis method for quantification of drug concentration is one of the essential issues in pharmacokinetic and therapeutic drug monitoring studies.

Objective:

A fast and reliable dispersive liquid-liquid microextraction procedure was employed for preconcentration of verapamil in exhaled breath condensate (EBC) samples and this was followed by the determination with high-performance liquid chromatography-ultraviolet detection.

Methods:

A reverse-phase high-performance liquid chromatography (RP-HPLC) combined with a dispersive liquid-liquid microextraction method (DLLME) was applied for quantification of verapamil in the EBC samples. The developed method was validated according to FDA guidelines.

Results:

Under the optimum conditions, the method provided a linear range between 0.07 and 0.8 µg.mL-1 with a coefficient of determination of 0.998. The intra- and inter-day relative standard deviation and relative error values of the method were below 15%, which indicated good precision and accuracy. The proposed method was successfully applied for the analysis of verapamil in two real samples with concentrations of 0.07 and 0.09 µg.mL-1.

Conclusion:

The established HPLC-UV-DLLME method could be applied for the analysis of verapamil in human EBC samples.

HPLC/MS findings in a fatality involving sustained-release verapamil

A fatality involving verapamil, a calcium channel blocker agent, is presented. A 51-year old male ingested 7200 mg of sustained-release (SR) verapamil at T0 and died 40 hours later of refractory, mixed shock and multiorgan failure. The symptoms displayed during hospitalization were quite typical and involved altered consciousness, hypotension, bradycardia, atrioventricular block, metabolic acidosis and renal failure. Verapamil and its primary metabolite, norverapamil, were assayed on eight plasma and two urine samples, successively taken between the admission to the ICU (T0-4 hours) and time of death, using an original high-performance liquid chromatography/mass spectrometry (HPLC/MS) procedure with verapamil-d3 as internal standard. Plasma verapamil and norverapamil levels on admission were 0.94 and 1.36 mg/mL, respectively, then verapamil remained practically unchanged throughout the hospitalization (0.85 mg/mL at T0-40 hours). The discussion focuses on the detrimental role of SR formulations in overdose, with special emphasis on the risk of pharmacobezoar development already reported with SR-verapamil. To our knowledge, this is the first report of a verapamil fatality documented by repeated plasma measurements of the drug during the antemortem period.

Surface-assisted laser desorption ionization mass spectrometry techniques for application in forensics

Matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS) is an excellent analytical technique for the rapid and sensitive analysis of macromolecules (>700 Da), such as peptides, proteins, nucleic acids, and synthetic polymers. However, the detection of smaller organic molecules with masses below 700 Da using MALDI-MS is challenging due to the appearance of matrix adducts and matrix fragment peaks in the same spectral range. Recently, nanostructured substrates have been developed that facilitate matrix-free laser desorption ionization (LDI), contributing to an emerging analytical paradigm referred to as surface-assisted laser desorption ionization (SALDI) MS. Since SALDI enables the detection of small organic molecules, it is rapidly growing in popularity, including in the field of forensics. At the same time, SALDI also holds significant potential as a high throughput analytical tool in roadside, work place and athlete drug testing. In this review, we discuss recent advances in SALDI techniques such as desorption ionization on porous silicon (DIOS), nano-initiator mass spectrometry (NIMS) and nano assisted laser desorption ionization (NALDI™) and compare their strengths and weaknesses with particular focus on forensic applications. These include the detection of illicit drug molecules and their metabolites in biological matrices and small molecule detection from forensic samples including banknotes and fingerprints. Finally, the review highlights recent advances in mass spectrometry imaging (MSI) using SALDI techniques.

Detection limit enhancement of antiarrhythmic drugs in human plasma using capillary electrophoresis with dispersive liquid–liquid microextraction and field-amplified sample stacking method

Background: A new capillary zone electrophoresis (CZE) with ultraviolet detection method has been developed and validated for the analysis of four antiarrhythmic drugs in human plasma samples. Methods: In this study, a dispersive liquid–liquid microextraction (DLLME) coupled with field-amplified sample stacking (FASS) was employed for biological samples clean-up and sensitivity enhancement in CZE. Results: Under optimum DLLME-FASS-CZE conditions, enhancement factors were in the range of 157–314. The method was validated over the concentration range of 20–800 ng/ml in human plasma. Inter- and intra-day precision and the accuracy were less than 20%; the detection limits ranged from 2.5 to 4.7 ng/ml. Furthermore, the validated method was successfully applied to the detection of studied drugs in patients’ plasma samples.

Enantiomeric separation of verapamil and its active metabolite, norverapamil, and simultaneous quantification in human plasma by LC-ESI-MS-MS

A simple, selective and high-throughput liquid chromatography-tandem mass spectrometry method has been developed and validated for the chromatographic separation and quantification of (R)- and (S)-enantiomers of verapamil and its active metabolite, norverapamil, in human plasma. All four analytes along with deuterated internal standards (D(6)-verapamil and D(6)-norverapamil) were extracted from 50 µL human plasma by liquid-liquid extraction. Separation was achieved on a Chiralcel OD-RH (150 × 4.6 mm, 5 µm) analytical column with resolution factors of 1.4 and 1.9 for (R)- and (S)-enantiomers of verapamil and norverapamil, respectively. A mobile phase consisting of 0.05% trifluoroacetic acid in water-acetonitrile (70:30, v/v) afforded capacity factors of 2.45, 3.05, 2.27 and 3.13 for (R)- and (S)-enantiomers of verapamil and norverapamil, respectively. Detection was carried out on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring and positive ion modes. The method was validated over the concentration range of 1.0-250.0 ng/mL for all four analytes. Absolute recovery for the analytes ranged from 91.1 to 108.1%. Matrix factors calculated at three quality control levels varied from 0.96-1.07. The method was successfully applied to a pharmacokinetic study in 18 healthy Indian males after oral administration of a 240-mg verapamil tablet formulation under fasting conditions.

Development of 2D chiral chromatography with accelerator mass spectrometry for quantification of 14C-labeled R- and S-verapamil in plasma

Background: A microdose study was performed where 50 µg R/S-14C-verapamil was dosed intravenously to human volunteers. In order to quantify the individual R- and S-enantiomers in human plasma a 2D chiral HPLC method with subsequent analysis by accelerator mass spectrometry was verified. Results: R/S-verapamil was separated on a C18 column and the isolated fraction was applied to a chiral column where the verapamil enantiomers were separated. Experimental recovery (∼73% [coefficient of variation {CV} = 16%] and 66% [CV = 21%] for R- and S-verapamil, respectively) was accounted for by the use of internal standardization from the fluorescence response of nonlabeled R- and S-verapamil. The precision of the assay ranged from 4.1 to 15.9% CV and the limit of quantitation was 1.95–4.81 pg/ml for R-verapamil and 1.76–3.34 pg/ml for S-verapamil. Conclusion: This method was successfully applied to the analysis of R- and S-verapamil in human plasma.

Perfusion studies of glyburide transfer across the human placenta: implications for fetal safety

OBJECTIVE

Gestational diabetes affects up to 5% of women. Oral hypoglycemics have been avoided because of the assumption that their placental transfer may cause fetal-neonatal hypoglycemia. A recent randomized trial could not show measurable glyburide levels in umbilical blood despite maternal treatment with regular doses of glyburide. The mechanism underlying this phenomenon is not known. The objective of our study was to document, using a human placenta perfusion model, whether glyburide is actively effluxed from the fetal to the maternal circulation.

STUDY DESIGN

In vitro perfusion studies of human cotyledon were performed to quantify placental transfer of glyburide. Using close circle experiments and introducing glyburide to both maternal and fetal circulations at 200 ng/mL, we looked for evidence of transport against concentration gradient from the fetus to the mother. In parallel experiments, the P-glycoprotein inhibitor verapamil was used in an attempt to inhibit transplacental glyburide movement.

RESULTS

There was highly significant transfer of glyburide against concentration gradient from the fetal to the maternal circulation. Fetal-to-maternal concentration ratio was 0.92 +/- 0.23 at the start of the experimental period and 0.31 +/- 0.47 3 hours later (P = .01) (n = 5). Verapamil did not modify glyburide transport.

CONCLUSION

This is the first direct evidence of active glyburide transport from the fetus to the mother and, in general, of any medicinal drug used during pregnancy. These experiments suggest that glyburide is actively efflux by a transporter other than P-glycoprotein. Alternatively, it is possible that a minority of glyburide is carried by P-glycoprotein, but most of the fetal load is pumped to the mother by a yet-unidentified placental transport system.

Direct determination of verapamil in urine and serum samples by micellar liquid chromatography and fluorescence detection

Verapamil, a calcium channel antagonist, is one of the most commonly prescribed drugs in the treatment of hypertension. In this work, it was determined in serum and urine samples by a sensitive and precise chromatographic procedure without any pre-treatment step in a C18 column using a micellar mobile phase of 0.15M sodium dodecyl sulfate and 5% pentanol at pH 7. Fluorescence detection set at 230 nm (excitation) and 312 nm (emission) was used. Verapamil is eluted at 12.5 min with no interference by the protein band or endogenous compounds. Linearities (r > 0.998), as well as intra- and inter-day precision, were studied in the validation of the method. LODs were also calculated to be 11.0, 18.5 and 20.2 ng/mL in micellar solution, serum and urine, respectively. Recoveries in the biological matrices were in the 97-99% range. Drug excretion in urine was studied in a volunteer receiving treatment for hypertension, and verapamil, as an unchanged drug, was separated from other metabolites. The procedure developed can be useful in the field of toxicology and clinical analysis.

Verapamil drug metabolism studies by automated in-tube solid phase microextraction

Verapamil is a common calcium antagonist described with antianginal, antihypertensive and antiarrythmic properties. The metabolites of verapamil have also shown pharmacological properties and therefore sample preparation and analysis techniques capable of metabolic screening for verapamil are important. In-tube SPME is a relatively new method integrating sample extraction, concentration and introduction into one single step without the use of organic solvents. The capability of in-tube SPME in bioanalysis has been reviewed but there has been no application described in the field of drug metabolism. Since automation and interfacing of in-tube SPME coupled to liquid chromatography-mass spectrometry (LC-MS) is possible, we confirm in this study that it is a powerful method to monitor the main metabolites of verapamil in various biological matrices like plasma, urine and cell culture media. Further, we show that it could also be used in routine pharmacokinetics measurements. An in-tube SPME LC-MS method was developed to extract and analyze the metabolic profile of verapamil from biological matrices. The detection limit for verapamil, gallopamil, norverapamil and PR22 were 52, 53, 65 and 83 ng/ml (UV detection) and 5, 6, 6 and 8 ng/ml (MS detection), respectively. The precision of the method was calculated in various biological matrices and the average % R.S.D. (N=5) for verapamil, gallopamil, norverapamil and PR22 was 3.9, 3.7, 3.8 and 4.3% (MS detection), respectively. The linear dynamic range was determined to be 100-800 ng/ml (UV detection) with a total sample preparation and analysis time of 34 min.

Pharmacokinetics of verapamil and its metabolite norverapamil from a buccal drug formulation

Pharmacokinetics of verapamil and its metabolite norverapamil, from buccal drug formulation administered in a dose 20 mg in relation to conventional tablets of verapamil 40 mg, used in medical practice, was determined. Buccal formulation has previously been designed as an alternative form of dosing verapamil. Bioavailability was determined by a crossover method in 12 healthy volunteers. Drug concentration in plasma was determined by means of HPLC with a fluorescence detector. For buccal formulation the average values of C(max) and AUC(0-24 h) for verapamil were much higher than for the reference Staveran tablets and amounted to 51.28 and 320.23 ng/ml h, respectively. However, for norverapamil the corresponding values for buccal formulation were much lower than for a conventional tablet. It has been demonstrated that the proposed buccal verapamil dosing ensures different metabolism of the drug as compared to tablets. Better parameters of bioavailability of verapamil from buccal formulation of twice a smaller dose than that in the tablet, prove that this new drug might be form more effective clinically than the conventional one.

Pharmacokinetics of verapamil and norverapamil from controlled release floating pellets in humans

Pharmacokinetics of verapamil (V) in a dose of 40 mg and its metabolite norverapamil (N) from the new oral drug formulation in a form of capsule filled with floating pellets was determined. Conventional 40-mg tablets used in a medical practice served as a reference. Bioavailability studies were carried out in 12 healthy volunteers including six men and six women. In an in vitro test the pellets floated on the surface of the extraction fluid for 6 h. Mean value of maximum plasma concentration (C(max)) of V for floating pellets was 28.27 ng ml(-1) and t(max) 3.75 h. The value of the area under the concentrations versus time, AUC(0-infinity) was calculated as 364.65 ng ml(-1) h, biological half-lives of the absorption and elimination (t(0.5el)) phase were 0.5 h and 10.68 h, respectively. For the reference conventional tablets those values were 33.07 ng ml(-1), 1.21 h, 224.22 ng ml(-1) h, 0.36 h and 6.17 h, respectively. The average concentration of N in plasma was similar to that of V.