Preparation of Antihypertensive Drugs in Biological Matrix with Solvent Front Position Extraction for LC–MS/MS Analysis

Solvent front position extraction procedure was used to prepare biological samples containing selected antihypertensive drugs (ramipril, lercanidipine, indapamide, valsartan, hydrochlorothiazide, perindopril, and nebivolol). Substances separated from the biological matrix components (bovine serum albumin) were quantified by means of liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Sample preparation process was performed with the use of a prototype horizontal chamber with a moving pipette driven by a 3D printer mechanism enabling a controlled eluent flow velocity. Application of this device was advantageous for simultaneous preparation of several samples for further quantitative analysis, with a synchronized reduction of manual operations and solvent consumption. Quantitative results obtained for the majority of the investigated antihypertensive drugs in a complex biological matrix were satisfactory. The values of the %RSD were around 5% for six of the seven substances (with the exception of indapamide). The method exhibits a suitable accuracy (the relative error percentage was below 10% for most drugs). The values of LOD and LOQ were in the range of 1.19 µg/L–8.53 µg/L and 3.61 µg/L–25.8 µg/L, respectively.

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.

High-throughput quantification of 8 antihypertensive drugs and active metabolites in human plasma using UPLC-MS/MS

BACKGROUND

To assess drug adherence of patients with hypertension, an analytical method was developed and validated using ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). The method includes eight frequently prescribed antihypertensive drugs from four classes and their active metabolites: angiotensin converting enzyme inhibitors enalapril and perindopril (active metabolites respectively enalaprilate and perindoprilate), angiotensin II receptor blockers losartan (with the active metabolite losartan carboxylic acid) and valsartan, calcium channel blockers amlodipine and nifedipine and diuretics hydrochlorothiazide and spironolactone (with the active metabolite canrenone).

METHODS

The antihypertensive drugs were analyzed using a simple and fast sample preparation protocol with protein precipitation followed by chromatographic separation using a gradient elution on a reversed phase column. Mass spectrometric detection was conducted by applying both positive and negative electrospray ionization (ESI+/ESI-) and selected reaction monitoring mode (MS/MS). Only 50μl of plasma sample is needed for the simultaneous quantification of all 12 compounds within 6min run-to-run analysis time. Enalapril-d5 was applied as internal standard for all compounds except hydrochlorothiazide (internal standard: Hydrochlorothiazide-13C,d2).

RESULTS

The method was validated according to FDA guidelines. Matrix effects were examined using the method of Matuszewski. Correlation coefficients were higher than 0.995 for all compounds. Intra- and inter-day accuracies were <15% for all analytes except spironolactone (-16.8%) in the established linear range. Intra- and inter-day precision were <15% for all analytes. As a result of the lower sensitivity of hydrochlorothiazide, the lowest three calibration levels were excluded.

DISCUSSION/CONCLUSIONS

The described method is suitable for the simultaneous quantitative analysis of the most commonly used antihypertensive drugs and their corresponding active metabolites. Major advantages are minimal sample volume and clean up and a short runtime. The method is now available to monitor drug adherence of patients with resistant hypertension in our hospital.

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.