Rapid and sensitive liquid chromatography/tandem mass spectrometry method for simultaneous determination of enalapril and its major metabolite enalaprilat, in human plasma: Application to a bioequivalence study

Development of a novel integrated isothermal amplification system for detection of bacteria-spiked blood samples

Bloodstream infection (BSI) caused by bacteria is highly pathogenic and lethal, and easily develops whole-body inflammatory state. Immediate identification of disease-causing bacteria can improve patient prognosis. Traditional testing methods are not only time-consuming, but such tests are limited to laboratories. Recombinase polymerase amplification combined with lateral flow dipstick (RPA-LFD) holds great promise for rapid nucleic acid detection, but the uncapping operation after amplification easily contaminates laboratories. Therefore, the establishment of a more effective integrated isothermal amplification system has become an urgent problem to be solved. In this study, we designed and fabricated a hermetically sealed integrated isothermal amplification system. Combining with this system, a set of RPA-LFD assays for detecting S. aureus, K. peneumoniae, P. aeruginosa, and H. influenza in BSI were established and evaluated. The whole process could be completed in less than 15 min and the results can be visualized by the naked eye. The developed RPA-LFD assays displayed a good sensitivity, and no cross-reactivity was observed in seven similar bacterial genera. The results obtained with 60 clinical samples indicated that the developed RPA-LFD assays had high specifcity and sensitivity for identifying S. aureus, K. peneumoniae, P. aeruginosa, and H. influenza in BSI. In conclusion, our results showed that the developed RPA-LFD assay is an alternative to existing PCR-based methods for detection of S. aureus, K. peneumoniae, P. aeruginosa, and H. influenza in BSI in primary hospitals.

Low-volume LC-MS/MS method for the pharmacokinetic investigation of carvedilol, enalapril and their metabolites in whole blood and plasma: Application to a paediatric clinical trial

Evidence-based pharmacotherapy with carvedilol and enalapril in children suffering from heart failure is insufficient owing to limited pharmacokinetic data. Although a few data sets regarding enalapril, its metabolite enalaprilat and carvedilol in children have been published, pharmacokinetic data on carvedilol metabolites are missing. However, for both drug substances, their active metabolites contribute substantially to drug efficacy. As data can hardly be derived from adults owing to the unknown impacts of enzymatic maturation and ontogeny during childhood, customised assays are important to facilitate paediatric evidence-based pharmacotherapy. Considering ethical paediatric constraints, a low-volume liquid chromatography coupled to mass spectrometry (LC-MS/MS) assay was developed using whole blood or plasma for the quantification of enalapril, enalaprilat, carvedilol, O-desmethyl carvedilol, 4- and 5-hydroxyphenyl carvedilol as well as 3- and 8-hydroxy carvedilol. To facilitate broader applications in adults, the elderly and children, a wide calibration range-between 0.024/0.049 and 50.000 ng/ml-was achieved with good linearity (r ≥ 0.995 for all analytes). In compliance with international bioanalytical guidelines, accuracy, precision, sensitivity and internal standard normalised matrix effects were further successfully validated with the exception of those for 3-hydroxy carvedilol, which was therefore assessed semi-quantitatively. Distinct haematocrits did not impact matrix effects or recoveries when analysing whole blood. Blood-to-plasma ratios were determined for all analytes to form the basis for pharmacokinetic modelling. Finally, incurred sample reanalysis of paediatric samples confirmed the reproducibility of the developed low-volume LC-MS/MS method during study sample analysis. The assay facilitates the reliable generation of important data and contributes towards a safe drug therapy in children.

Validated LC-MS/MS method for the simultaneous determination of enalapril maleate, nitrendipine, hydrochlorothiazide, and their major metabolites in human plasma

Hypertension is a major risk factor for atherosclerosis and ischemic heart disease. Most hypertensive patients need a combination of antihypertensive agents to achieve therapeutic goals. A rapid, sensitive, and selective liquid chromatography-tandem mass spectrometric method was developed and validated for simultaneous determination of enalapril maleate (ENA) and its major metabolite enalaprilat (ENAT), nitrendipine (NIT) and its major metabolite dehydronitrendipine (DNIT), and hydrochlorothiazide (HCT) in human plasma using felodipine as an internal standard (IS). The drugs were extracted from plasma using one-step protein precipitation. Chromatographic separation was performed on a Symmetry C₁₈ column, with water and acetonitrile (10:90, v/v) as mobile phase. The detection was carried out using multiple reaction monitoring mode and coupled with electrospray ionization source. Multiple reaction monitoring transitions were m/z 377.1 → 234.1 for ENA, m/z 349.2 → 206.1 for ENAT, m/z 361.2 → 315.1 for NIT, m/z 359 → 331 for DNIT, m/z 295.9 → 205.1 for HCT, and m/z 384.1 → 338 for felodipine (IS). The method was linear over concentration ranges of 1-200, 20-500, 5-200, 2-100, and 5-200 ng/mL for ENA, ENAT, NIT, DNIT, and HCT, respectively, with r² ≥ 0.99. Method validation was performed according to U.S. Food and Drug Administration guidelines. The validated method showed good sensitivity and selectivity and could be applied for therapeutic drug monitoring and bioequivalence studies.

User-Friendly HPLC Method Development and Validation for Determination of Enalapril Maleate and Its Impurities in Enalapril Tablets

The official method for the determination of Enalapril Maleate and its related substances in European Pharmacopoeia (EP) is a gradient liquid chromatographic method. The method used styrene-divinylbenzene copolymer column, mobile phase buffer pH 6.8 and column oven temperature 70°C. In this method, the separation between main component Enalapril and Ph. Eur. Imp-A was not completed hence the achieving system suitability requirement is a tough task and it requires quite often adjustment in chromatographic parameters. Moreover, column oven temperature 70°C is not user friendly to HPLC instruments and users. In this study, several changes were introduced to the method in order to improve the separation, peak shapes and to overcome the column oven temperature. A new user-friendly stability-indicating RP-HPLC method was developed for Enalapril related substances analysis. The developed method uses a ZORBAX Eclipse XDB-C18 column with column oven temperature at 55°C and mobile phase containing acetonitrile and a phosphate buffer at pH 3.0. The method is capable of separating all the known impurities with resolution more than 3.5, which is much better than that obtained with the existing monograph methods. The optimized method was validated and demonstrated to have acceptable specificity, sensitivity, linearity, accuracy, precision, robustness, solution stability and equivalency to the EP method. The developed method proved to be applicable to a wide number of C18 reversed-phase columns. In addition, the Enalapril assay method also presented with 20 min run time.

Pharmacokinetics and drug-drug interaction between enalapril, enalaprilat and felodipine extended release (ER) in healthy subjects

Since angiotensin-converting enzyme (ACE) inhibitors and calcium antagonists have complimentary mechanisms of action, enalapril, an ACE inhibitor, is used in combination with felodipine, a vascular selective dihydropyridine calcium antagonist, for the treatment of hypertension. The present study was designed to investigate the possible drug-drug interaction between these two agents in Chinese healthy subjects. A randomized, open-label, multiple-dose, 3-treatment, 3-period, 6-sequence cross-over study enrolling 12 healthy subjects (six male and six female subjects) was performed. Plasma pharmacokinetic studies were performed after 5 mg of enalapril and 5 mg of felodipine were administered alone or concomitantly twice per day for six days, and once in the morning of day seven. All 12 healthy subjects (mean [SD] age, 24.3 [2.8] years; body weight, 57.3 [5.7] kg; height, 163.2 [5.2] cm) completed all scheduled pharmacokinetic studies. Geometric mean ratios (with 90% CIs) of AUC_τ,ss and C_max,ss for enalapril administered concomitantly with felodipine vs. enalapril administered alone were 1.025 (0.80-1.25) and 1.065 (0.70-1.43), respectively. Geometric mean ratios (with 90% CIs) of AUC_τ,ss and C_max,ss for felodipine administered concomitantly with enalapril vs. felodipine administered alone were 1.14 (0.97-1.31) and 0.80 (0.65-0.95), respectively. There were no severe or serious drug-related adverse events observed during the study. Our results revealed that the co-administration of enalapril and felodipine affected the pharmacokinetics of felodipine, but not that of enalapril. Although the difference in PK parameters was statistically significant, its clinical significance may be limited, considering safety profile observed in the present study.

A Liquid Chromatography-Tandem Mass Spectrometry Method for Evaluation of Two Brands of Enalapril 20 mg Tablets in Healthy Human Volunteers

Enalapril is an angiotensin-converting enzyme inhibitor used for treatment of hypertension and chronic heart disease. Enalaprilat is its active metabolite responsible for the activity. This study aimed to develop and validate a method for enalapril and enalaprilat analysis and to determine the bioequivalence of two tablet formulae of enalapril. LC-MS/MS bioanalytical method was developed and validated and then applied to evaluate the bioavailability of two enalapril formulae. Antihyperglycemic sitagliptin was used as internal standard (IS). The method was accurate for the within- and between-days analysis, and precise CV% was <5%, being linear over the calibration range 1.0-200.0 ng/ml. Stability was >85% and the LOD was 0.907 and 0.910 ng/ml for enalapril and enalaprilat, respectively, and LLOQ was 1 ng/ml. The pharmacokinetic parameters C_max, t_max, AUC_0-72, and AUC_0-∞ values of enalapril and enalaprilat of the two formulae were calculated and nonsignificant differences were found. A linearity, specific, accurate, and precise method was developed and applied for the analysis of enalapril and enalaprilat in human plasma after oral administration of two formulae of enalapril 20 mg tablets in healthy volunteers. Depending on the statistical analysis it was concluded that the two enalapril formulae were bioequivalent.

LC-MS/MS assay for quantitation of enalapril and enalaprilat in plasma for bioequivalence study in Indian subjects

Background:

Enalapril (EPL) is an angiotensin-converting enzyme inhibitor for the treatment of hypertension and chronic heart failure. Enalaprilat (EPLT) is an active metabolite that contributes to the overall activity of EPL.

Aim:

To quantitate EPL along with its metabolite EPLT using LC–MS/MS, a bioanalytical method was developed and validated with tolbutamide in human plasma using a protein precipitation technique.

Results:

The sensitive and selective method has an LLOQ of 1 ng/ml with a linearity range of 1–500 ng/ml for both EPL and EPLT using 300 µl of plasma without any matrix effect.

Conclusion:

Linearity, specificity, accuracy, precision and stability, as well as its application to the analysis of plasma samples after oral administration of 20 mg of EPL maleate in healthy volunteers demonstrate applicability to bioavailability/bioequivalence studies.

The present study describes a sensitive, selective, simple, accurate and reproducible LC–MS/MS method for the simultaneous determination of both enalapril (EPL) and enalaprilat (EPLT) in human plasma. The results obtained indicate the high sensitivity of the described method for analysis of EPL and EPLT, which render this method particularly useful for pharmacokinetic or bioequivalence studies. The proposed method has been applied for the analysis of EPL and EPLT in the plasma of healthy volunteers in a single-dose pharmacokinetic study.

Tailored Assays for Pharmacokinetic and Pharmacodynamic Investigations of Aliskiren and Enalapril in Children: An Application in Serum, Urine, and Saliva

OBJECTIVES

Drugs that are effectively used to treat hypertension in adults (e.g., enalapril) have not been sufficiently investigated in children. Studies required for pediatric approval require special consideration regarding ethics, study design, and conduct and are also associated with special demands for the bioanalytic method. Pediatric-appropriate assays can overcome these burdens and enable systematic investigations of pharmacokinetics and pharmacodynamic in all pediatric age groups.

METHODS

Tailored assays were developed for pharmacokinetic investigation of a drug in 100 μL of serum, saliva, and urine. All assays were applied in a proof-of-concept study to 22 healthy volunteers who had been given 300 mg aliskiren hemifumarate or 20 mg enalapril maleate and allowed for dense sampling. Changes in humoral parameters of the renin-angiotensin-aldosterone system were also evaluated with 6 parameters in 2.1 mL blood per time point.

RESULTS

The pharmacokinetic results of aliskiren and enalapril obtained by low-volume assays in serum and urine were comparable to that noted in the literature. The dense sampling enabled very detailed concentration-time profiles that showed high intersubject variability and biphasic absorption behavior of aliskiren. The replacement of invasive sampling by saliva collection appears inappropriate for both drugs because the correlations of drug concentrations in both fluids were low. A low-volume assay was also used to determine values for in the renin-angiotensin-aldosterone system and to compare those results with the published literature.

CONCLUSION

These results support both the use of low-volume assays in pediatric research and the systematic investigation of their use in neonates and infants. Use of this assay methodology will increase information about drug pharmacokinetics and pharmacodynamics in this vulnerable population and might contribute to safe and effective use of pharmacotherapy.

Sample Preparation and Extraction in Small Sample Volumes Suitable for Pediatric Clinical Studies: Challenges, Advances, and Experiences of a Bioanalytical HPLC-MS/MS Method Validation Using Enalapril and Enalaprilat

In USA and Europe, medicines agencies force the development of child-appropriate medications and intend to increase the availability of information on the pediatric use. This asks for bioanalytical methods which are able to deal with small sample volumes as the trial-related blood lost is very restricted in children. Broadly used HPLC-MS/MS, being able to cope with small volumes, is susceptible to matrix effects. The latter restrains the precise drug quantification through, for example, causing signal suppression. Sophisticated sample preparation and purification utilizing solid-phase extraction was applied to reduce and control matrix effects. A scale-up from vacuum manifold to positive pressure manifold was conducted to meet the demands of high-throughput within a clinical setting. Faced challenges, advances, and experiences in solid-phase extraction are exemplarily presented on the basis of the bioanalytical method development and validation of low-volume samples (50 μL serum). Enalapril, enalaprilat, and benazepril served as sample drugs. The applied sample preparation and extraction successfully reduced the absolute and relative matrix effect to comply with international guidelines. Recoveries ranged from 77 to 104% for enalapril and from 93 to 118% for enalaprilat. The bioanalytical method comprising sample extraction by solid-phase extraction was fully validated according to FDA and EMA bioanalytical guidelines and was used in a Phase I study in 24 volunteers.

Recent Advances in Mass Spectrometry for the Identification of Neuro-chemicals and their Metabolites in Biofluids

Recently, mass spectrometric related techniques have been widely applied for the identification and quantification of neurochemicals and their metabolites in biofluids. This article presents an overview of mass spectrometric techniques applied in the detection of neurological substances and their metabolites from biological samples. In addition, the advances of chromatographic methods (LC, GC and CE) coupled with mass spectrometric techniques for analysis of neurochemicals in pharmaceutical and biological samples are also discussed.