Column-switching high-performance liquid chromatographic (HPLC) determination of hydrochlorothiazide in rat, dog, and human plasma

An LC-MS/MS Method for Determination of Triple Drugs Combination of Valsartan, Amlodipine and Hydrochlorothiazide in Human Plasma for Bioequivalence Study

Background:

Current guidelines for the treatment of hypertension recommend combination therapy, which intends to control blood pressure and enhance cardiovascular protection.

Materials and Methods:

A sensitive, reliable and selective tandem mass spectrometry (LC-MS/MS) method has been developed for simultaneous quantification of amlodipine (AML), valsartan (VAL) and hydrochlorothiazide (HCTZ) in human plasma. The chromatographic system was equipped with ACE 5 C8 (50 X 2.1 mm) column and utilized a mobile phase composition of 0.5 mM Ammonium Chloride & 0.04% FA-Methanol (45:55% v/v). The method used three internal standards; AML-D4, HCTZ-D2 C13 and VAL-D3 with 10% intra- and inter-day precision, and 6% bias for all the analytes.

Results:

The assay was found to be linear with R-2 > 0.998, and the limits of quantification for AML, VAL and HCTZ were 0.2, 50.0 and 2.0 ng/mL, respectively. The analytes were found to be stable in plasma samples over short and long term storage.

:

The developed method is rapid with a run time of 3.5 min and cost-effective since the simple sample preparation method is adopted. This method was successfully applied for the bioequivalence study of AML, VAL, and HCTZ in human plasma after administration of the fixed-dose combination tablet of (10/160/25 mg). Pharmacokinetic parameters (Cmax and AUC0-72) for AML and (Cmax, AUC0-t, AUC0-∞) for VAL and HCTZ were used for bioequivalence assessment. These were determined by noncompartmental analysis of concentration data.

Conclusion:

The result showed 90% confidence intervals (obtained by ANOVA) which were within the predefined ranges. As a consequence, this method can be successfully applied for measuring and quantifying a large number of samples.

Determination of hydrochlorothiazide in human plasma by liquid chromatography/tandem mass spectrometry

In this study, a fast and sensitive liquid chromatography/tandem mass spectrometry method for determination of hydrochlorothiazide in human plasma was developed and validated. The analyte and irbesartan, used as the internal standard, were precipitated and extracted from plasma using methanol. Analysis was performed on a Phenomenex Kromasil C(8) column with water and methanol (27:73, v/v) as the mobile phase. Linearity was assessed from 0.78 to 200 ng/mL in plasma. The analytical method proved to be applicable in a pharmacokinetic study after oral administration of 12 mg hydrochlorothiazide tablets to 20 healthy volunteers.

Simultaneous determination of losartan, EXP-3174 and hydrochlorothiazide in plasma via fully automated 96-well-format-based solid-phase extraction and liquid chromatography–negative electrospray tandem mass spectrometry

An automated, sensitive and high-throughput liquid chromatographic/electrospray tandem mass spectrometric (LC-MS/MS) assay was developed for the simultaneous determination of losartan (LOS), its major circulating metabolite EXP-3174 and hydrochlorothiazide (HCTZ) in human plasma. LOS and HCTZ coexist in the same drug formulation, and this is the first method that enables the simultaneous determination of both drugs along with the active metabolite of LOS. Since these drugs have different physicochemical properties, the employment of a liquid-liquid extraction (LLE) protocol was precluded. A fully automated solid-phase extraction (SPE) protocol, based on 96-well format plates, was used to isolate these compounds and furosemide (internal standard, IS) from plasma. Washing and elution steps were amended accordingly in order to minimize any matrix effect from components of the plasma without reducing the elution of the molecules of interest. The compounds were eluted from a C18 column and detected with an API 3000 triple-quadrupole mass spectrometer using negative electrospray ionization and multiple reaction monitoring (MRM). The assay was linear over the range 1.00-400 ng/mL for LOS and EXP-3174 and 0.500-200 ng/mL for HCTZ, respectively, when 200 microl of plasma was used in the extraction. The overall intra- and interassay variations were within acceptance limits. The analysis time for each sample was 4 min, and more than 300 samples could be analyzed in one day by running the system overnight. The assay was simple, highly sensitive, selective, precise, fast, and it enables the reliable determination of LOS, EXP-3174 and HCTZ in pharmacokinetic or bioequivalence studies after per os administration of a single tablet containing both drugs.

Sensitive liquid chromatography-tandem mass spectrometry method for quantification of hydrochlorothiazide in human plasma

A simple, rapid, sensitive and specific liquid chromatography-tandem mass spectrometry method was developed and validated for quantification of hydrochlorothiazide (I), a common diuretic and anti-hypertensive agent. The analyte and internal standard, tamsulosin (II) were extracted by liquid-liquid extraction with diethyl ether-dichloromethane (70:30, v/v) using a Glas-Col Multi-Pulse Vortexer. The chromatographic separation was performed on a reversed-phase column (Waters symmetry C18) with a mobile phase of 10 mm ammonium acetate-methanol (15:85, v/v). The protonated analyte was quantitated in negative ionization by multiple reaction monitoring with a mass spectrometer. The mass transitions m/z 296.1 solidus in circle 205.0 and m/z 407.2 solidus in circle 184.9 were used to measure I and II, respectively. The assay exhibited a linear dynamic range of 0.5-200 ng/mL for hydrochlorothiazide in human plasma. The lower limit of quantitation was 500 pg/mL, with a relative standard deviation of less than 9%. Acceptable precision and accuracy were obtained for concentrations over the standard curve ranges. A run time of 2.5 min for each sample made it possible to analyze a throughput of more than 400 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability or bioequivalence studies.

Liquid extraction and HPLC-DAD assay of hydrochlorothiazide from plasma for a bioequivalence study at the lowest therapeutic dose

The main parameters considered in optimizing the liquid extraction and quantitative assay were the yield, precision, limit of quantification, time required for extraction and concentration, and quantity of solvent. The influence on these parameters of the following factors was examined: nature of the extracting solvent, quantity of solvent, co-extraction solvent, and duration of stirring. Instead of equilibrium parameters of the involved thermodynamic system, a kinetic approach was preferred in terms of the effective partition 'constant', which is not really constant but a function of time and extraction conditions. The final selected method, considered to be rapid and simple, was applied to determine the pharmacokinetics of hydrochlorotiazide (HCT) after administration of Capozide (Bristol-Myers Squibb) tablets containing 50 mg Captopril and 25 mg HCT, to 4 healthy volunteers. The results obtained were in accordance with the pharmacokinetic parameters of HCT reported in the literature.

3-Bromomethyl-propyphenazone as a new derivatization reagent for high performance liquid chromatography of captopril and hydrochlorothiazide with UV-detection

3-Bromomethyl-propyphenazone (BMP) was used as a derivatization reagent for the detection and quantification of captopril (CAP) and hydrochlorothiazide (HCT) by high performance liquid chromatography using Zorbax C8 column, and 0.05M sodium acetate, acetonitrile, methanol (14:17:4; pH 6.5) as mobile phase system with UV-detection at 254 nm. The cited reagent reacts with the mercapto and amino groups of CAP and HCT in acetone using anhydrous potassium carbonate as hydrobromide acceptor. The reaction was completed within 30 min for CAP and 60 min for HCT with heating at 105 +/- 5 degrees C in mini-reaction vial. The linear concentration ranges for both CAP and HCT were 8 to 160 and 6 to 140 ng per injection, respectively. The derivatized captopril was synthesized and confirmed with spectral analysis. This method was applied for determination of spiked captopril in human urine after extraction with Extrelut-20 column using ethyl acetate:isopropanol (85:15 v/v) as eluant.

Simultaneous determination of citalopram and its metabolites by high-performance liquid chromatography with column switching and fluorescence detection by direct plasma injection

High-performance liquid chromatography with a successive column-switching technique was developed for simultaneous determination of citalopram and its four metabolites in plasma. Plasma samples were injected directly, and the target compounds were purified and concentrated with an inexpensive commercial octadecyl guard column. Then, the six-port valve was switched, and the compounds retained in the column were eluted by the back-flush method using 20 mM phosphate buffer (pH 4.6)-acetonitrile (70:30, v/v) containing 0.1% diethylamine and separated with an ODS column. The compounds were assayed with a fluorescence detector at an excitation wavelength of 249 nm and an emission wavelength of 302 nm. At least 30 plasma samples could be treated with an octadecyl guard column. The limits of quantitation of this method were 2.0 ng/ml for citalopram, desmethylcitalopram, didesmethylcitalopram, citalopram propionic acid and citalopram N-oxide. This method was applied to a pharmacokinetic study in dogs and a toxicokinetic study in rats.

Determination of 2'-deoxy-3'-thiacytidine (3TC) in human urine by liquid chromatography: direct injection with column switching

3TC (GR109714X) is a cytidine dideoxynucleoside analogue which has been shown to have in vitro activity against a variety of strains of HIV-1 and is currently being investigated in clinical trials as a treatment for HIV infection. An HPLC method for the determination of 3TC in human urine has been developed and validated. The method allows direct injection of urine (10 microliters) using HPLC column switching followed by UV detection. On-line extraction is performed using a Spherisorb-SCX (5 microns, 20 x 4.0 mm) eluted with deionized water at 1 ml min-1. 3TC is retained while the bulk of urine constituents are eluted to waste. The SCX column is then backflushed to a BDS-Hypersil-C18 (5 microns, 250 x 4.6 mm) and eluted with 100 mM acetate pH 4.5-methanol (95:5, v/v) for final separation. 3TC is detected by UV absorbance at lambda = 285. The quantitation range of the assay was 0.5-500 micrograms ml-1. The method has demonstrated sufficient ruggedness to be used in support of 3TC clinical trials. Application to other cytidine analogues including DDC has been demonstrated.

Column-switching liquid chromatographic determination of ML-1035 sulphoxide and its sulphone and sulphide metabolites in rat urine

A fully automated column-switching LC assay has been developed for the simultaneous determination of a gastroprokinetic agent, ML-1035 sulphoxide, and its sulphone and sulphide metabolites in rat urine. ML-1035 Sulphoxide is a metoclopramide analogue. The method involved direct injection of a diluted urine sample into a CN extraction column for sample clean-up. Polar urine components, including proteins, were flushed to waste. The retained compounds were then eluted onto a C8 analytical column for further separation and analysis by fluorescence detection. After the subsequent washing and re-equilibration with a sequence of three solvent mixtures, the extraction column was ready for the next injection. The recovery of the compounds from the extraction column was 85-90%. The limit of quantitation for all compounds of interest was 25 ng ml-1 or lower, using a 100 microliters specimen of urine. Good inter-day precision (2.1-10.0%), accuracy (0.3-18.0%), and linearity were obtained for all compounds over a range of 25-1000 ng ml-1. The applicability of the LC method was validated with urine samples from rats that had received ML-1035 sulphoxide.