Plasma Trough Concentrations of Antihypertensive Drugs for the Assessment of Treatment Adherence: A Meta-Analysis.

Biochemical drug screening by liquid chromatography-tandem mass spectrometry in plasma is an accurate method for the quantification of plasma concentrations of antihypertensive medications in patients with hypertension. Trough concentrations could possibly be used as drug-specific cutoff values in the biochemical assessment of (non-)adherence. We performed a literature review and meta-analysis of pharmacokinetic studies to determine plasma trough concentrations of amlodipine, hydrochlorothiazide, and valsartan. PubMed was searched for pharmacokinetic studies up to September 2020. Eligible studies reported steady-state mean trough concentration and their variance. Pooled trough concentrations were estimated using a three-level random effects meta-analytic model. Moderator analyses were performed to explore sources of heterogeneity. One thousand three hundred eighteen potentially relevant articles were identified of which 45 were eligible for inclusion. The pooled mean trough concentration was 9.2 ng/mL (95% CI, 7.5-10.8) for amlodipine, 41.0 ng/mL (95% CI, 17.4-64.7) for hydrochlorothiazide, and 352.9 ng/mL (95% CI, 243.5-462.3) for valsartan. Substantial heterogeneity was present for all 3 pooled estimates. Moderator analyses identified dosage as a significant moderator for the pooled trough concentration of amlodipine (ß1=0.9; P<0.05), mean age, and mean body weight for the mean trough concentration of hydrochlorothiazide (ß1=2.2, P<0.05, respectively, ß1=-4.0, P<0.05) and no significant moderators for valsartan. Plasma trough concentrations of amlodipine, hydrochlorothiazide, and valsartan, measured with liquid chromatography-tandem mass spectrometry, are highly heterogeneous over the different studies. Use of the pooled trough concentration as a cutoff in the biochemical assessment of adherence can result in inaccurate diagnosis of (non-)adherence, which may seriously harm the patient-physician relationship, and is therefore not recommended.

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.

Applications of shun shell column and nanocomposite sorbent for analysis of eleven anti-hypertensive in human plasma.

High-performance liquid chromatography (HPLC) and solid phase micro membrane tip extraction (SPMMTE) methods are developed for the simultaneous analysis of eleven cardiovascular drugs in human plasma. Iron nanoparticles were obtained by the green method, characterized by XRD, FT-IR, TEM, and EDS and utilized in SPMMTE for sample preparation. The mobile phase used was ammonium acetate buffer-methanol-acetonitrile (65:18:17) with a 1.0 mL/min flow rate at 260 nm detection. Column used was Sunshell C18 150 × 4.6 mm, 2.6 µm. The values of k, α, and Rs were ranged from 040 to109.22, 1.20 to 2.67 and 1.0 to 26.18. SPMMTE and HPLC methods were fast, reproducible, precise, robust, economic and rugged for analysis of methyldopa, hydrochlorothiazide, prazosin hydrochloride, furosemide, labetalol, propranolol, valsartan, losartan potassium, diltiazem, irbesartan and spironolactone in human plasma. The recoveries (%) of methyldopa, hydrochlorothiazide, prazosin hydrochloride, furosemide, labetalol, propranolol, valsartan, losartan potassium, diltiazem, irbesartan, and spironolactone were 91.0, 85.2, 92.3, 90.4, 90.1, 85.6, 86.6, 86.2, 85.1, 86.6, and 85.7, respectively. These results showed that SPMMTE and HPLC methods can be applied to test the described drugs in several matrices.

A High Throughput HPLC-MS/MS Method for Antihypertensive Drugs Determination in Plasma and Its Application on Pharmacokinetic Interaction Study with Shuxuetong Injection in Rats.

A high-throughput HPLC-MS/MS method was developed and validated for the determination of four antihypertensive drugs including metoprolol tartrate, hydrochlorothiazide, nifedipine, and valsartan in rat plasma. The Sprague-Dawley rats were randomly divided into three groups: A Group: gastric-administration of metoprolol tartrate, hydrochlorothiazide, nifedipine, or valsartan; B Group: a single intravenous injection of SXT, then dosing as the A group; C Group: daily injection of SXT through the tail vein for 8 consecutive days and dosing as the A group on the eighth day. For metoprolol tartrate and valsartan, blood samples were collected before administration and at time points 0.03, 0.08, 0.17, 0.25, 0.5, 1, 2, 4, 6, 8, 10, 12, and 24 h from the fossa orbitalis vein. For hydrochlorothiazide and nifedipine, the time points were 0, 0.08, 0.17, 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 10, 12, and 24 h. The plasma samples containing different individual antihypertensive drug were mixed and prepared by protein precipitation with methanol. The chromatographic separation was performed on an Agilent Eclipse Plus C18 column (2.1 mm×100 mm, 3.5 µm) using gradient elution with mobile phase consisting of acetonitrile and water (containing 0.1% formic acid). The flow rate was 0.3 mL/min. The detection was accomplished on a tandem mass spectrometer with an electrospray ionization (ESI) source by multiple reaction monitoring (MRM) in both positive and negative modes. The method was successfully applied to a pharmacokinetic interaction study of Shuxuetong injection on the antihypertensive drugs. The results suggested that SXT could increase the total amount of metoprolol tartrate and nifedipine in plasma and showed little influence on the pharmacokinetic behaviors of hydrochlorothiazide and valsartan.

Reliable and easy-to-use LC-MS/MS-method for simultaneous determination of the antihypertensives metoprolol, amlodipine, canrenone and hydrochlorothiazide in patients with therapy-refractory arterial hypertension.

BACKGROUND: Therapy-refractory arterial hypertension is defined as a blood pressure (BP) in a subset of patients who fail to achieve BP control despite a three-drug regimen (including a diuretic). Various factors have impact on loss of therapy response. Drug-drug-interactions (DDIs) may cause altered pharmacokinetics (PK) of antihypertensive drugs. Upregulation of activity and expression of cytochrome P450 (CYP) enzymes can result in decreased plasma drug levels. Besides these PK considerations a significant problem could be nonadherence to drug therapy. In this regard Therapeutic Drug Monitoring (TDM) is a useful tool for detecting nonadherence. Therefore a LC-MS/MS-method for determination of Metoprolol (MET), Amlodipine (AML), Canrenone (CAN) and Hydrochlorothiazide (HCT) was developed. METHODS: An UHPLC-MS/MS method was developed and validated for simultaneous determination of MET, AML, CAN and HCT in plasma matrix. Extraction of serum samples consisted of simple protein precipitation using acetonitrile. Stable isotope labeled analogues for each antihypertensive were obtained for internal standardization and quantitative analysis ([2H7]-MET, ([13C6]-AML, [2H4]-CAN, [13C6]-HCT). Calibrators and quality controls were prepared in plasma matrix of normal individuals. Sample preparation: protein precipitation with acetonitrile and addition of internal standard-mix. RESULTS: All analytes were eluted within a runtime of 2.5 min. Linearity experiments were demonstrated in plasma over following concentration ranges: MET: 5-750 µg/l, AML: 1-50 µg/l, CAN: 10-500 µg/l, HCT: 5-500 µg/l (R2 > 0.993). Chromatographic separation was achieved using a C18 column (50 × 2.1 mm, 1.9 µm particle size) and an isocratic elution. LC-MS/MS analyses were performed on a triple quadrupole mass spectrometer using positive and negative electrospray ionization in selected reaction monitoring (SRM) mode. Ion transitions monitored for quantitation were m/z 268.2 → 74.1 for MET, m/z 409.1 → 238.0 for AML, m/z 341.2 → 91.0 for CAN and m/z 296.0 → 205.1 for HCT. For all analytes, inter- and intra-day precision (CV, %) varied between 1.7 and 14.0 and inter- and intra-day accuracy values ranged from -2.5 to 7.1%. The lower limits of detection and quantification were: 0.08 and 0.23; 0.05 and 0.15; 2.82 and 8.54; and 0.02 and 0.05 µg/l for MET, AML, CAN and HCT, respectively. Results of stability experiments were within the required range of +/- 15%. CONCLUSIONS: Although the level of recommendation of TDM of antihypertensive drugs in patients with refractory hypertension is not yet established, the present LC-MS/MS-method can serve as an effective tool for detection of PK-alterations/nonadherence and may help to monitor antihypertensive pharmacotherapy.

Simultaneous ultraperformance liquid chromatography/tandem mass spectrometry determination of four antihypertensive drugs in human plasma using hydrophilic-lipophilic balanced reversed-phase sorbents sample preparation protocol.

Therapeutic drug monitoring of angiotensin-converting enzyme inhibitors has a great impact on blood pressure control in patients with heart failure and hepatic and renal impairment. To provide an efficient tool for drug assessment in plasma, a UPLC-MS/MS method was developed for simultaneous determination of benazepril hydrochloride, fosinopril sodium, captopril and hydrochlorothiazide in human plasma samples. Solid phase extraction was applied for sample preparation using OASIS® hydrophilic-lipophilic balanced reversed-phase sorbents cartridges. Chromatographic separation was performed using an Agilent SB-C18 column and methanol-0.1% formic acid in water (95:5, v/v) as mobile phase, at flow rate 0.3 mL/min. Detection was accomplished using a tandem mass spectrometer. The method was validated according to US Food and Drug Administration guidelines. It showed good linearity over concentration ranges 5-400 ng/mL for benazepril hydrochloride, fosinopril sodium and hydrochlorothiazide and 100-3500 ng/mL for captopril. CV% values were <13.92% whereas the mean accuracy ranged from 94.50 to 113.82% for quality control samples and their extraction recoveries ranged from 90.60 to 99.38%. In conclusion, the present study revealed method selectivity and sensitivity; it can be applied for estimation of angiotensin converting enzyme inhibitors and hydrochlorothiazide in human plasma for dose adjustment and therapeutic drug monitoring.

Quantification of Hydrochlorothiazide and Ramipril/Ramiprilate in Blood Serum and Cerebrospinal Fluid: A Pharmacokinetic Assessment of Central Nervous System Adverse Effects.

BACKGROUND: A drug must reach the central nervous system (CNS) in order to directly cause CNS adverse effects (AEs). Our current study addressed the pharmacokinetic (PK) background of the assumption that CNS concentrations of hydrochlorothiazide (HCT) and ramiprilate may directly cause CNS AEs such as headache and drowsiness. METHODS: In neurological patients, paired serum and cerebrospinal fluid (CSF) samples were withdrawn simultaneously. Some of them were treated with HCT (n = 15, daily chronic doses 7.5-25 mg) or ramipril (n = 9, 2.5-10 mg). Total concentrations of HCT and ramiprilate were quantified in these samples. To this end, sensitive liquid chromatography/tandem mass spectrometry methods were developed. RESULTS: CSF reached 4.1% (interquartile ranges 2.5-5%) of total serum concentrations for HCT and 2.3% (1.7-5.7%) for ramiprilate, corresponding to about 11.3% and 5.5% of respective unbound serum concentrations. CONCLUSION: The PK/Pharmacodynamic characteristics of HCT and ramiprilate in the CNS are unknown. However, since the CSF levels of these agents, both free and bound, were much lower than the corresponding concentrations in serum, it is unlikely that the observed CNS AEs are mediated primarily via direct effects in the brain.

Challenges in Simultaneous Determination of Hydrochlorothiazide and Ramipril in Human Plasma: Application to a Bioequivalence Study.

An isotope dilution selective and sensitive high-performance liquid chromatography-tandem mass spectrometry (LC-ESI-MS/MS) method has been developed for the simultaneous determination of hydrochlorothiazide (HCTZ) and ramipril in human plasma through a new concept of periodical polarity switching. Extraction of HCTZ, ramipril and their deuterated analogs as internal standards (ISs) was carried out from 150 µL of human plasma by solid-phase extraction method. Chromatographic separation of analytes was performed on Hypurity C18 (150 mm × 4.6 mm, 5 µ) column under gradient conditions with methanol:0.2% (v/v) formic acid in water as the mobile phase. The method was validated over a concentration range of 0.750-300 ng/mL for HCTZ and 0.125-80.0 ng/mL for ramipril. The mean extraction recovery for analytes and ISs were >(86.0%), consistent across all four QC levels. The challenges to evaluate matrix effect and continuous reproducibility of method during long analytical run was studied and resolved. Processed samples, freeze-thaw, long-term and whole blood stability were evaluated for both the analytes. The method was applied to support a bioequivalence study of 25 mg of HCTZ and 5 mg of ramipril tablet formulation in nine healthy Indian subjects. Assay reproducibility was demonstrated by reanalysis of 42 incurred samples.

Green-modified micellar liquid chromatography for isocratic isolation of some cardiovascular drugs with different polarities through experimental design approach.

Bilayer pseudo-stationary phase micellar liquid chromatography (MLC) was developed for simultaneous isocratic isolation of hydrochlorothiazide, as a basic-polar (hydrophilic) cardiovascular drug, as well as triamterene and losartan potassium, as acidic-nonpolar (hydrophobic) cardiovascular drugs. Utilizing a deep eutectic solvent (DES), as a novel green mobile phase additive in combination with acetonitrile (ACN) and acetic acid (ACA), drastically improved the chromatographic behavior of the drugs. Concentration of sodium dodecyl sulphate (SDS), as well as volume percentages of ACN, DES, and ACA were optimized by using a central composite design. The optimal composition of the mobile phase (0.12 mol L-1 SDS, 5% ACN, 4% DES, and 2% ACA) was chosen through the desirability function. The chromatographic peaks of both hydrophilic and hydrophobic drugs, respectively, emerged at high and low retention time values in the shortest total analysis time of 20 min (at a flow rate of 2 mL min-1). Analytical characterization of the developed approach was investigated through Food and Drug Administration (FDA) guidelines. Applicability of the method was evaluated by analysing of human plasma samples which were directly injected into the system.

Hansen solubility parameters for assay method optimization of simvastatin, ramipril, atenolol, hydrochlorothiazide and aspirin in human plasma using liquid chromatography with tandem mass spectrometry.

A simple, specific, sensitive, validated method was developed using liquid chromatography with tandem mass spectrometry with electrospray ionization of human plasma for the simultaneous estimation of drugs (simvastatin, ramipril, atenolol, hydrochlorothiazide, and aspirin) of PolycapTM capsule used in cardiovascular therapy. The interaction of these actives including internal standards between the stationary and mobile phase were investigated using Hansen solubility parameters. Chromatographic separation was performed on Phenomenex Synergi Polar-RP (30 × 2 mm, 4 µm) column with a gradient mobile phase composition of acetonitrile and 5 mM ammonium formate for positive mode and 0.1% formic acid in both water and acetonitrile for negative mode. The flow rate and runtime were 1.0 mL/min and 3.5 min, respectively. Sample extraction was done by protein precipitation using acetonitrile, enabling a fast analysis. The calibration ranges from 0.1 to 100, 0.1 to 100, and 1 to 1000 ng/mL for simvastatin, ramipril, and atenolol using internal standard carbamazepine in positive mode, respectively, whereas it was 0.3-300 and 2-2000 ng/mL for hydrochlorothiazide and aspirin using internal standard 7-hydroxy coumarin in negative mode, respectively. Hansen solubility parameters can be used as a high-throughput optimizing tool for column and mobile phase selection in bioanalysis. This validated bioanalytical method has the potential for future fixed dose combination based preclinical and clinical studies that can save analysis time.

Bioequivalence study between a fixed-dose single-pill formulation of nebivolol plus hydrochlorothiazide and separate formulations in healthy subjects using high-performance liquid chromatography coupled to tandem mass spectrometry.

Systemic arterial hypertension is a major risk factor for cerebrovascular disease. Therefore, adequate control of blood pressure is of enormous importance. One of the many fixed-dose single-pill antihypertensive formulations available on the market is the combination of nebivolol and hydrochlorothiazide. The objective of this study was to develop two distinct high-performance liquid chromatography coupled to tandem mass spectrometry methods to simultaneously quantify nebivolol and hydrochlorothiazide in human plasma. The methods were employed in a bioequivalence study, the first assay involving a nebivolol fixed-dose single-pill formulation based on healthy Brazilian volunteers. Nebilet HCT™ (nebivolol 5 mg + hydrochlorothiazide 12.5 mg tablet, manufactured by Menarini) was the test formulation. The reference formulations were Nebilet™ (nebivolol 5 mg tablet, manufactured by Menarini) and Clorana™ (hydrochlorothiazide 25 mg tablet, manufactured by Sanofi). For both analytes, liquid-liquid extraction was employed for sample preparation and the chromatographic run time was 3.5 min. The limits of quantification validated were 0.02 ng/mL for nebivolol and 1 ng/mL for hydrochlorothiazide. Since the 90% CI for Cmax , AUC(0-last) and AUC(0-inf) individual test/reference ratios were within the 80-125% interval indicative of bioequivalence, it was concluded that Nebilet HCT™ is bioequivalent to Nebilet™ and Clorana™.

COMPARATIVE BIOAVAILABILITY OF A FIXED-DOSE COMBINATION TABLET OF OLMESARTAN MEDOXOMIL/HYDROCHLOROTHIAZIDE IN HEALTHY KOREAN VOLUNTEERS.

Combination therapy with diuretics and angiotensin II type 1 (AT1) receptor antagonist is frequently recommended for the control of blood pressure in hypertensive patients. This study was targeted to compare pharmacokinetic profiles of a new generic fixed-dose combination (FDC) tablet of olmesartan medoxomil/hydrochlorothiazide 20/12.5 mg and a reference formulation of Olmetec Plus 20/12.5 mg tablets in healthy volunteers. The study design was a randomized sequence and two-way crossover study in healthy subjects. They were to be randomly assigned to either one of the two sequence groups; each subject sequentially received a single oral dose of reference and test tablet with 7-day washout period. Blood sample was collected at pre-dose and at 0.33, 0.67, 1, 1.33, 1.67, 2, 2.5, 3, 4, 6, 8, 12, 24, 36 and 48 h post-dose. The blood concentrations were analyzed by LC-MS/MS. Both of the 90% CI for the treatment ratios (test/reference) of C(max) and AUC(last) were to be in the range of 0.800-1.250 with regards to olmesartan medoxomil and hydrochlorothiazide; the geometric mean ratios (test/reference) for olmesartan C(max) and AUC(last) were 0.979 (90% CI, 0.934-1.027) and 0.992 (0.946-1.041), respectively, and those for hydrochlorothiazide C(max) and AUC(last) were 0.966 (0.975-1.110) and 0.999 (0.963-1.038), respectively. No serious adverse events were reported during the study. The generic formulation of olmesartan medoxomil/hydrochlorothiazide 20/12.5 mg tablet was bioequivalent with the reference formulation of Olmetec Plus 20/12.5 mg tablet in regards to the pharmacokinetic parameters of olmesartan medoxomil and hydrochlorothiazide. Clinical Research Information Service (CRIS) Registration Number: KCT0001025. (https://cris.nih.go.kr/ Mar 18, 2014)

Development of Sustained Release "NanoFDC (Fixed Dose Combination)" for Hypertension - An Experimental Study.

OBJECTIVES: The present study was planned to formulate, characterize and evaluate the pharmacokinetics of a novel "NanoFDC" comprising three commonly prescribed anti-hypertensive drugs, hydrochlorothiazide (a diuretic), candesartan (ARB) and amlodipine (a calcium channel blocker). BASIC METHODS: The candidate drugs were loaded in Poly (DL-lactide-co-gycolide) (PLGA) by emulsion- diffusion-evaporation method. The formulations were evaluated for their size, morphology, drug loading and in vitro release individually. Single dose pharmacokinetic profiles of the nanoformulations alone and in combination, as a NanoFDC, were evaluated in Wistar rats. RESULTS: The candidate drugs encapsulated inside PLGA showed entrapment efficiencies ranging from 30%, 33.5% and 32% for hydrochlorothiazide, candesartan and amlodipine respectively. The nanoparticles ranged in size from 110 to 180 nm. In vitro release profile of the nanoformulation showed 100% release by day 6 in the physiological pH 7.4 set up with PBS (phosphate buffer saline) and by day 4-5 in the intestinal pH 1.2 and 8.0 set up SGF (simulated gastric fluid) and SIF (simulated intestinal fluid) respectively. In pharmacokinetic analysis a sustained-release for 6 days and significant increase in the mean residence time (MRT), as compared to the respective free drugs was noted [MRT of amlodipine, hydrochlorothiazide and candesartan changed from 8.9 to 80.59 hours, 11 to 69.20 hours and 9 to 101.49 hours respectively]. CONCLUSION: We have shown for the first time that encapsulating amlodipine, hydrochlorothiazide and candesartan into a single nanoformulation, to get the "NanoFDC (Fixed Dose Combination)" is a feasible strategy which aims to decrease pill burden.

Pharmacokinetic properties and bioequivalence of two irbesartan/ hydrochlorothiazide fixed-dose combination tablets in healthy male Chinese volunteers.

OBJECTIVES: The aim of the present study was to compare the pharmacokinetic profiles between a new generic and a branded reference formulation of irbesartan/ hydrochlorothiazide FDC tablets, and to assess the bioequivalence of the two products in healthy Chinese male volunteers. MATERIALS AND METHODS: 24 male healthy volunteers participated in the open-label, single-dose, randomized-sequence, 2-way crossover study. Eligible subjects were randomly assigned (1:1) to receive a single 300/12.5-mg dose of either the test or reference formulation followed by a 1-week washout. Blood samples were obtained before (0 hours) and 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, 24, 36, 48, and 72 hours after dosing. Plasma concentrations of irbesartan and hydrochlorothiazide were analyzed by two separate validated liquid chromatography/tandem mass spectrometric (LC-MS/MS) methods. RESULTS: For irbesartan, the 90% confidence intervals (CIs) of AUC0-t, AUC0-∞, and Cmax were 103.27-116.71%, 105.01-121.47%, and 84.15-96.88%, respectively. For hydrochlorothiazide, the 90% CIs of AUC0-t, AUC0-∞, and Cmax were 96.11-109.02%, 95.15-107.35%, and 91.66-101.40%, respectively. A total of 3 mild AEs were reported in 3 subjects (12.5%). CONCLUSION: In this study, a single dose (300/12.5-mg) of the test formulation of irbesartan and hydrochlorothiazide FDC tablet in fasting healthy Chinese male volunteers met WHO's and China's FDA regulatory criteria for assumption of bioequivalence to the reference formulation based on AUC and Cmax. Both formulations were well tolerated.

Simultaneous Determination of Aliskiren Hemifumarate, Amlodipine Besylate and Hydrochlorothiazide in Spiked Human Plasma Using UPLC-MS/MS.

A sensitive UPLC-MS/MS method was developed and validated for simultaneous estimation of aliskiren hemifumarate (ALS), amlodipine besylate (AML) and hydrochlorothiazide (HCZ) in spiked human plasma using valsartan as an internal standard (IS). Liquid-liquid extraction was used for purification and pre-concentration of analytes. The mobile phase consisted of 0.1% formic acid in ammonium acetate buffer (0.02 M, pH 3.5) and methanol (25:75, v/v), flowing through XBridge BEH (50 × 2.1 mm ID, 5 µm) C18 column, at a flow rate of 0.6 mL min(-1). Multiple reaction monitoring (MRM) transitions were measured using an electrospray source in the positive ion mode for ALS and AML, whereas HCZ and IS were measured in negative ion mode. Validation of the method was performed as per US-FDA guidelines with linearity in the range of 2.0-400.0, 0.3-25.0 and 5.0-400.0 ng mL(-1) for ALS, AML and HCZ, respectively. In human plasma, ALS, AML and HCZ were stable for at least 1 month at -70 ± 5°C and for at least 6 h at ambient temperature. After extraction from plasma, the reconstituted samples of ALS, AML and HCZ were stable in the autosampler at ambient temperature for 6 h. The LC-MS/MS method is suitable for bioequivalence and pharmacokinetic studies of this combination.

Pharmacokinetic drug-drug interaction assessment between LCZ696, an angiotensin receptor neprilysin inhibitor, and hydrochlorothiazide, amlodipine, or carvedilol.

LCZ696 is a first-in-class angiotensin receptor neprilysin inhibitor in development for treatments of hypertension and heart failure indications. In 3 separate studies, pharmacokinetic drug-drug interactions (DDIs) potential was assessed when LCZ696 was coadministered with hydrochlorothiazide (HCTZ), amlodipine, or carvedilol. The studies used a open-label, single-sequence, 3-period, crossover design in healthy subjects. Blood samples were collected to determine the pharmacokinetic parameters of LCZ696 analytes (AHU377, LBQ657, and valsartan), HCTZ, amlodipine, or carvedilol (R[+]- and S[-]-carvedilol) for statistical analysis. When coadministered LCZ696 with HCTZ, the 90% CIs of the geometric mean ratios of AUCtau,ss of HCTZ and that of LBQ657 were within a 0.80-1.25 interval, whereas HCTZ Cmax,ss decreased by 26%, LBQ657 Cmax,ss increased by 19%, and the AUCtau,ss and Cmax,ss of valsartan increased by 14% and 16%, respectively. Pharmacokinetics of amlodipine, R(+)- and S(-)-carvedilol, or LBQ657 were not altered after coadministration of LCZ696 with amlodipine or carvedilol. Coadministration of LCZ696 400 mg once daily (qd) with HCTZ 25 mg qd, amlodipine 10 mg qd, or carvedilol 25 mg twice a day (bid) had no clinically relevant pharmacokinetic drug-drug interactions. LCZ696, HCTZ, amlodipine, and carvedilol were safe and well tolerated when given alone or concomitantly in the investigated studies.

Development and validation of bioanalytical method for simultaneous estimation of ramipril and hydrochlorothiazide in human plasma using liquid chromatography-tandem mass spectrometry.

The present study describes a novel liquid chromatographic-tandem mass spectrometric (LC-MS/MS) method for the simultaneous estimation of ramipril (RAM) and hydrochlorothiazide (HCTZ) in human plasma using liquid-liquid extraction technique. This method made use of electrospray ionization in positive mode for RAM and in negative mode for HCTZ using triple quadrupole mass spectrometry where carbamazepine was used as an internal standard (IS). Analytes were recovered by methyl tertiary butyl ether:dichloromethane (85:15) subsequently separated on an Enable C18 G column (150 mm × 4.6 mm, 5 µm) using methanol:0.1% formic acid in water (85:15) as a mobile phase, at a flow rate of 0.5 mL/min. Quantification of RAM, HCTZ and IS was performed using multi-reaction monitoring mode (MRM) where transition of m/z 417.2→234.1 (RAM) and 237.0→194.0 (IS) in positive mode and 296.1→205.0 for HCTZ in negative mode. The calibration curve was linear (r(2)>0.99) over the concentration range of 2-170 ng/mL for RAM and 8-680 ng/mL for HCTZ. The intra-day and inter-day precisions were <15% and the accuracy was all within ±15% (at LLOQ level ±20%). Additionally, the LC-MS/MS method was fully validated for all the other parameters such as selectivity, matrix effect, recovery and stability as well. In conclusion, the findings of the present study revealed the selectivity and sensitivity of this method for the simultaneous estimation of RAM and HCTZ in human plasma.

[Troubleshooting of bioinequivalence of compound valsartan tablets].

The study aims to evaluate the bioequivalence of valsartan hydrochlorothiazide tablets, and to investigate the potential cause of bioinequivalence. This was a single-center study with an open, randomized double-way crossover design. Test and reference preparations containing 160 mg of valsartan and 25 mg of hydrochlorothiazide were given to 36 healthy male volunteers. Plasma concentrations of valsartan and hydrochlorothiazide were determined simultaneously by LC-MS/MS. The pharmacokinetic parameters and relative bioavailability were calculated, while the bioequivalence between test and reference preparations were evaluated. The dissolution profiles of test and reference preparations in four different mediums were determined via dissolution test and HPLC. The similarity was investigated according to the similarity factors (f2). The F(o-t) and F(0-infinity) were (139.4 +/- 65.2)% and (137.5 +/- 61.2)% for valsartan of test preparations. It led to get the conclusion that test and reference preparations were not bioequivalent for valsartan. A significant difference was observed between test and reference tablets in the valsartan dissolution test of pH 1.2 hydrochloric acid solution. The key factor of the bioinequivalence might be that dissolution of valsartan in acid medium has marked difference between two preparations.

Simultaneous determination of irbesartan and hydrochlorothiazide in human plasma by ultra high performance liquid chromatography tandem mass spectrometry and its application to a bioequivalence study.

An ultra high performance liquid chromatography tandem mass spectrometry (U-HPLC-MS/MS) method was developed and validated to determine irbesartan (IRB) and hydrochlorothiazide (HCTZ) in human plasma simultaneously. Plasma samples were prepared using protein precipitation with acetonitrile, the two analytes and the internal standard losartan were separated on an Acquity U-HPLC BEH C18 column and mass spectrometric analysis was performed using a QTrap5500 mass spectrometer coupled with an electro-spray ionization (ESI) source in the negative ion mode. The MRM transitions of m/z 427.2→206.9 and m/z 296.1→204.9 were used to quantify for IRB and HCTZ, respectively. The linearity of this method was found to be within the concentration range of 5-3000ng/mL for IRB, and 0.5-300ng/mL for HCTZ in human plasma, respectively. The lower limit of quantification (LLOQ) was 5ng/mL and 0.5ng/mL for IRB and HCTZ in human plasma, respectively. The relative standard deviations (RSD) of intra and inter precision were less than 12% for both IRB and HCTZ. The analysis time of per sample was 2.5min. The developed and validated method was successfully applied to a bioequivalence study of IRB (300mg) with HCTZ (12.5mg) tablet in Chinese healthy volunteers (N=20).

Pharmacokinetic interactions between topiramate and diltiazem, hydrochlorothiazide, or propranolol.

Drug-drug interactions between topiramate and diltiazem, hydrochlorothiazide, or propranolol were evaluated along with safety/tolerability in three open-label studies. Healthy participants (aged 18-45 years) received topiramate 75 mg every 12 hours (q12h) and diltiazem 240 mg/day (study 1); topiramate 96 mg q12h and hydrochlorothiazide 25 mg/day (study 2); topiramate 100 mg q12h and propranolol 40-80 mg q12h (study 3). The pharmacokinetic parameters for topiramate, diltiazem (and active metabolites, desacetyldiltiazem [DEA], N-demethyl diltiazem [DEM]), hydrochlorothiazide, and propranolol (and its active metabolite) were assessed at steady state. Results showed no effect of diltiazem on topiramate pharmacokinetics. However, a modest reduction in systemic exposures of diltiazem and DEA (10-27%) occurred during coadministration with topiramate. Systemic exposure of DEM was unaffected. Furthermore, oral and renal clearance of topiramate decreased (22-30%) significantly (P < 0.05) during coadministration with hydrochlorothiazide, while systemic exposure increased by 27-29%. Topiramate had no effect on hydrochlorothiazide pharmacokinetics. The results demonstrated lack of pharmacokinetic interaction between topiramate and propranolol. Overall, no new safety concerns emerged when topiramate was coadministered with diltiazem, hydrochlorothiazide, or propranolol.