Determination of doxazosin and verapamil in human serum by fast LC–MS/MS: Application to document non-compliance of patients

In Vitro and In Vivo Studies of a Verapamil-Containing Gastroretentive Solid Foam Capsule

Gastroretentive systems may overcome problems associated with incomplete drug absorption by localized release of the API in the stomach. Low-density drug delivery systems can float in the gastric content and improve the bioavailability of small molecules. The current publication presents verapamil–HCl-containing solid foam prepared by continuous manufacturing. Production runs were validated, and the foam structure was characterized by micro-CT scans and SEM. Dissolution properties, texture changes during dissolution, and floating forces were analyzed. An optimized formulation was chosen and given orally to Beagle dogs to determine the pharmacokinetic parameters of the solid foam capsules. As a result, a 12.5 m/m% stearic acid content was found to be the most effective to reduce the apparent density of capsules. Drug release can be described by the first-order model, where 70% of verapamil dissolved after 10 h from the optimized formulation. The texture analysis proved that the structures of the solid foams are resistant. Additionally, the floating forces of the samples remained constant during their dissolution in acidic media. An in vivo study confirmed the prolonged release of the API, and gastroscopic images verified the retention of the capsule in the stomach.

Systematic Optimization of Ambient Ionization Ion Mobility Mass Spectrometry for Rapid Separation of Isomers

Current methods typically used for metabolite screening and disease diagnosis often require extensive sample preparation, which increases analysis time and associated costs. While ambient ionization techniques enable the analysis of various samples in complex matrices with little or no sample preparation in a short time (typically within a minute), their reduced selectivity, even when coupled with high-resolution mass spectrometers, limits their application in certain fields. In this study, we have optimized the coupling of paper spray (PS) and leaf spray (LS) ambient ionization techniques with a commercially available ion mobility mass spectrometer (IM-MS) and demonstrated the separation of geometric and constitutional isomers. Ambient ionization techniques allow simultaneous introduction and ionization of samples, while background noise and matrix interference from paper and leaf substrates are filtered out by IM separation, resulting in high sensitivity and selectivity of the PS-IM-MS and LS-IM-MS workflows. In addition, we introduced a novel approach to perform single-field collision cross section (CCS) measurements, which resulted in CCS values that differ by 0.15% and 0.25% from traditional stepped-field and single-field methods, respectively. In addition, we used advanced computational tools to confidently identify analyte structures by comparing CCS values from experimental IM measurements and theoretical calculations. These results suggest that the coupling of ambient ionization methods with ion mobility techniques enables rapid, sensitive, and highly selective analysis that can be used in different fields, such as agrochemical screening and disease diagnostics.

Monitoring Antihypertensive Medication Adherence by LC-MS/MS: Method Establishment and Clinical Application

ABSTRACT

Proper medication compliance is critical for the integrity of clinical practice, directly related to the success of clinical trials to evaluate both pharmacological and device-based therapies. Here, we established a liquid chromatography tandem mass spectrometry (LC-MS/MS) method to accurately detect 55 chemical entities in human urine sample, which accounting for the most commonly used 172 antihypertensive drugs in China. The established method had good accuracy, intra-day and inter-day precision for all analyses in both bench tests and validated in 21 hospitalized patients. We utilized this method to monitor and ensure drug compliance, and exclude the inferring impacts of medication compliance as a key confounder for our pivotal trial of a catheter-based, renal mapping and selective renal denervation to treat hypertension. It is found that in the urine samples from 92 consecutive subjects, 85 subjects (92.4%) were consistent with their prescriptions after 28 days run-in periods, 90 (97.8%) and 85 (95.5%) patients completely complied with their medications during the 3-month and 6-month follow-up period, respectively. Thus, using LC-MS/MS method with specificity, accuracy and precision, we ensured drug compliance of patients, excluded the key confounder of drug interferences and ensured the quality of our device-based clinical trial for treatment of hypertension.

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.

Univariate calibrations with or without chemometric assistance for determination of drugs lacking peak maxima in their zero-order profiles

Trandolapril has no sharp peak in its zero-order spectrum and therefore, it is difficult to be measured by direct spectrophotometry. In this manuscript, several univariate and multivariate spectrophotometric methods were developed and validated for determination of Trandolapril (TR) and Verapamil (VR) combination. The first method for measuring Trandolapril is Constant Multiplication-Spectrum Subtraction (CM-SS), where Trandolapril was measured at 210 nm in its zero-order curve after elimination of Verapamil spectrum. Second and third methods are two Base Points (2BP) and area under the curve (AUC) to measure Trandolapril concentration without depending on the shoulder peak. The fourth method for Trandolapril is Derivative Subtraction (DS) that utilizes the sharp peak appeared in the first order spectrum of Trandolapril. Verapamil was determined by two methods, Constant Multiplication (CM) and Derivative Subtraction-Constant Multiplication (DS-CM). Also, two multivariate methods were developed for measurement of the mixture, Partial Least Squares (PLS) and Principal Component Regression (PCR). All the developed methods were validated as per ICH guidelines and the results proved that the developed methods are accurate and selective. Moreover, a statistical comparison between the developed methods and a reference method was done. Also, One-way ANOVA statistical test was done between all the proposed univariate and multivariate spectrophotometric methods.

Comparative pharmacokinetics of trandolapril, its active metabolite, and verapamil in human plasma of Egyptian population using HPLC-MS/MS

Trandolapril and verapamil are commonly used antihypertensive drugs. However, there is a lack of available data on the change of their pharmacokinetics in patients with liver or kidney impairment and hence the need for dose adjustment. In this article, a high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed and validated for the monitoring of trandolapril, its active metabolite trandolaprilat, and verapamil in human plasma of patients with renal impairment and/or liver insufficiency. The chromatographic separation was achieved on a Gemini C18 reversed phase column using a gradient elution mode with a run time of 10 minutes. The mobile phase consisted of a mixture of methanol and 2% acetic acid. The electrospray ionization MS/MS analysis was performed in multiple reaction monitoring (MRM) mode. The assay was validated as per Food and Drug Administration (FDA) guidelines for bioanalytical method validation and proved to be suitable for the determination of therapeutic drug levels in plasma. The inter-group changes in pharmacokinetic data were compared to that of healthy volunteers. The comparison showed a significant difference in the pharmacokinetic parameters between the studied groups. The presented results exhibit the benefits of the proposed assay as a validated analytical tool for the continuous drug monitoring.

Biochemical Screening for Nonadherence Is Associated With Blood Pressure Reduction and Improvement in Adherence

We hypothesized that screening for nonadherence to antihypertensive treatment using liquid chromatography-tandem mass spectrometry-based biochemical analysis of urine/serum has therapeutic applications in nonadherent hypertensive patients. A retrospective analysis of hypertensive patients attending specialist tertiary care centers was conducted in 2 European countries (United Kingdom and Czech Republic). Nonadherence to antihypertensive treatment was diagnosed using biochemical analysis of urine (United Kingdom) or serum (Czech Republic). These results were subsequently discussed with each patient, and data on follow-up clinic blood pressure (BP) measurements were collected from clinical files. Of 238 UK patients who underwent biochemical urine analysis, 73 were nonadherent to antihypertensive treatment. Their initial urinary adherence ratio (the ratio of detected to prescribed antihypertensive medications) increased from 0.33 (0-0.67) to 1 (0.67-1) between the first and the last clinic appointments. The observed increase in the urinary adherence ratio in initially nonadherent UK patients was associated with the improved BP control; by the last clinic appointment, systolic and diastolic BPs were ≈19.5 and 7.5 mm Hg lower than at baseline (P=0.001 and 0.009, respectively). These findings were further corroborated in 93 nonadherent hypertensive patients from Czech Republic-their average systolic and diastolic BPs dropped by ≈32.6 and 17.4 mm Hg, respectively (P<0.001), on appointments after the biochemical analysis. Our data show that nonadherent hypertensive patients respond to liquid chromatography-tandem mass spectrometry-based biochemical analysis with improved adherence and significant BP drop. Such repeated biochemical analyses should be considered as a therapeutic approach in nonadherent hypertensive patients.

Risk Factors for Nonadherence to Antihypertensive Treatment

Nonadherence to antihypertensive treatment is a critical contributor to suboptimal blood pressure control. There are limited and heterogeneous data on the risk factors for nonadherence because few studies used objective-direct diagnostic methods. We used high-performance liquid chromatography-tandem mass spectrometry of urine and serum to detect nonadherence and explored its association with the main demographic- and therapy-related factors in 1348 patients with hypertension from 2 European countries. The rates of nonadherence to antihypertensive treatment were 41.6% and 31.5% in the UK and Czech populations, respectively. Nonadherence was inversely related to age and male sex. Each increase in the number of antihypertensive medications led to 85% and 77% increase in nonadherence ( P <0.001) in the UK and Czech populations, respectively. The odds of nonadherence to diuretics were the highest among 5 classes of antihypertensive medications ( P ≤0.005 in both populations). The predictive model for nonadherence, including age, sex, diuretics, and the number of prescribed antihypertensives, showed area under the curves of 0.758 and 0.710 in the UK and Czech populations, respectively. The area under the curves for the UK model tested on the Czech data and for the Czech model tested on UK data were calculated at 0.708 and 0.756, respectively. We demonstrate that the number and class of prescribed antihypertensives are modifiable risk factors for biochemically confirmed nonadherence to blood pressure–lowering therapy. Further development of discriminatory models incorporating these parameters might prove clinically useful in assessment of nonadherence in countries where biochemical analysis is unavailable.

Highly sensitive spectrofluorimetric method for determination of doxazosin through derivatization with fluorescamine; Application to content uniformity testing

A highly sensitive, simple and selective spectrofluorimetric method has been developed and validated for determination of doxazosin mesylate in pure form, pharmaceutical formulations and human plasma. The method is based on the reaction between doxazosin mesylate and fluorescamine in Teorell buffer solution (pH 3) to give highly fluorescent derivative that can be measured at 489 nm using excitation wavelength of 385 nm. Different experimental parameters affecting the reaction were carefully studied and optimized. The calibration plot was constructed over the concentration range of 16-400 ng mL(-1) with quantitation limit of 14.3 ng mL(-1). The developed procedure was validated according to ICH guidelines and the results were satisfactory. The proposed method has been successfully applied to the analysis of the cited drug in its pharmaceutical preparations as well as for content uniformity testing. The results showed excellent agreement with the reported method with respect to precision and accuracy. In addition, the drug concentration was determined in the spiked human plasma by the suggested method with % recovery in the range of 96.2-98.3% (SD; 0.76-0.93, n=5).

Precise assessment of noncompliance with the antihypertensive therapy in patients with resistant hypertension using toxicological serum analysis

BACKGROUND

The aim of our study was to assess the prevalence of pseudo-resistance caused by noncompliance with treatment among patients with severe resistant hypertension and to analyze the contributing factors.

METHOD

Three hundred and thirty-nine patients (195 men) with resistant essential hypertension were studied. The first group consisted of 176 patients admitted for hospitalization for exclusion of a secondary cause to our hypertension centre (103 men); the second one consisted of 163 out-patients (92 men) investigated for the first time in an out-patient hypertension clinic. Unplanned blood sampling for assessment of serum antihypertensive drug concentrations by means of liquid chromatography-mass spectrometry was performed in all patients.

RESULTS

Our main finding is a surprisingly low compliance with drug treatment in out-patients with resistant hypertension (23% partially noncompliant and 24% totally noncompliant - in total, 47% prevalence of noncompliance). Eighty-one percent of hospitalized patients were positive, in 10% the results were partially positive and in 9% of the patients, the drugs were all negative. The compliance among hospitalized patients was probably better due to lower numbers of prescribed drugs and expected thorough investigation. More frequently, noncompliance was found in nonworking (potential purpose-built behaviour), younger and less well educated patients. The most frequent noncompliance was to doxazosine, spironolactone and hydrochlorothiazide. We have observed a surprisingly low compliance with treatment among out-patients with severe hypertension.

CONCLUSION

We conclude that the evaluation of antihypertensive drugs concentrations is a useful and precise method for assessment of noncompliance in patients with resistant hypertension. This evaluation is useful before starting the diagnostic work-up of secondary forms of hypertension and before assignment patients into protocols with new therapy modalities such as renal denervation.

Acceleration of tuberculosis treatment by adjunctive therapy with verapamil as an efflux inhibitor

RATIONALE

A major priority in tuberculosis (TB) is to reduce effective treatment times and emergence of resistance. Recent studies in macrophages and zebrafish show that inhibition of mycobacterial efflux pumps with verapamil reduces the bacterial drug tolerance and may enhance drug efficacy.

OBJECTIVES

Using mice, a mammalian model known to predict human treatment responses, and selecting conservative human bioequivalent doses, we tested verapamil as an adjunctive drug together with standard TB chemotherapy. As verapamil is a substrate for CYP3A4, which is induced by rifampin, we evaluated the pharmacokinetic/pharmacodynamic relationships of verapamil and rifampin coadministration in mice.

METHODS

Using doses that achieve human bioequivalent levels matched to those of standard verapamil, but lower than those of extended release verapamil, we evaluated the activity of verapamil added to standard chemotherapy in both C3HeB/FeJ (which produce necrotic granulomas) and the wild-type background C3H/HeJ mouse strains. Relapse rates were assessed after 16, 20, and 24 weeks of treatment in mice.

MEASUREMENTS AND MAIN RESULTS

We determined that a dose adjustment of verapamil by 1.5-fold is required to compensate for concurrent use of rifampin during TB treatment. We found that standard TB chemotherapy plus verapamil accelerates bacterial clearance in C3HeB/FeJ mice with near sterilization, and significantly lowers relapse rates in just 4 months of treatment when compared with mice receiving standard therapy alone.

CONCLUSIONS

These data demonstrate treatment shortening by verapamil adjunctive therapy in mice, and strongly support further study of verapamil and other efflux pump inhibitors in human TB.

Clinical applications of fast liquid chromatography: a review on the analysis of cardiovascular drugs and their metabolites

One of the major challenges facing the medicine today is developing new therapies that enhance human health. To help address these challenges the utilization of analytical technologies and high-throughput automated platforms has been employed; in order to perform more experiments in a shorter time frame with increased data quality. In the last decade various analytical strategies have been established to enhance separation speed and efficiency in liquid chromatography applications. Liquid chromatography is an increasingly important tool for monitoring drugs and their metabolites. Furthermore, liquid chromatography has played an important role in pharmacokinetics and metabolism studies at these drug development stages since its introduction. This paper provides an overview of current trends in fast chromatography for the analysis of cardiovascular drugs and their metabolites in clinical applications. Current trends in fast liquid chromatographic separations involve monolith technologies, fused-core columns, high-temperature liquid chromatography (HTLC) and ultra-high performance liquid chromatography (UHPLC). The high specificity in combination with high sensitivity makes it an attractive complementary method to traditional methodology used for routine applications. The practical aspects of, recent developments in and the present status of fast chromatography for the analysis of biological fluids for therapeutic drug and metabolite monitoring, pharmacokinetic studies and bioequivalence studies are presented.