Enhancing simultaneous determination of some angiotensin II receptor antagonists and amlodipine in plasma using HPTLC with fluorescence densitometry: Independent fluorescence detection of the co-administrative drugs in the mixture across various pH conditions.

A novel and highly sensitive high-performance thin-layer chromatographic (HPTLC) method was developed and validated to quantify a combination of five pharmaceutical mixtures spiked to human plasma. The compounds comprised Amlodipine (AML) along with five angiotensin II receptor antagonist drugs (AIIRAs), namely Olmesartan (OLM), Telmisartan (TLM), Candesartan (CAN), Losartan (LOS), and Irbesartan (IRB). HPTLC was performed on silica gel 60 F254 plates using a mobile phase of Toluene: ethyl acetate: methanol: acetone: acetic acid (6:1.5:1:0.5:1, v/v/v/v/v). In a pioneering move, a reflectance/fluorescence detection mode was employed to identify two concurrently administered drugs at different pH levels for the first time. This method utilized the same chromatographic system, incorporating a specific measurement for AML at a neutral medium to achieve its maximum fluorescence at a 360 nm excitation wavelength, and measuring emission using a 540 nm optical filter. The process involved obtaining a very low fluorescence response from AIIRA. Subsequently, to enhance AIIRA's fluorescence, the plate was sprayed with perchloric acid to transition to a strong acidic medium, ultimately attaining the maximum fluorescence of AIIRA using various excitation wavelengths and a 400 nm emission filter. Through this strategic process, we could optimize the fluorescence signals of both drugs, thereby elevating the sensitivity of detection for this drug combination. AML demonstrated a linear range of 18-300 ng/band, while AIIRAs drugs exhibited a linear range of 6-150 ng/band. The method satisfied the International Conference on Harmonization (ICH) criteria for recovery, precision, repeatability, and robustness, showcasing exceptional sensitivity. The approach was successfully applied to quantify AML and AIIRAs drugs in both bulk drug and plasma samples, achieving high recovery percentages and minimal standard deviations.

Bioanalytical Assessment of Plasma Concentrations of Angiotensin-Converting Enzyme II Inhibitors and Angiotensin Receptor Blockers: A Pilot Study Among Patients Hospitalized With Acute Heart Failure.

BACKGROUND: Although angiotensin-converting enzyme II inhibitors (ACEIs) and angiotensin II receptor blockers (ARBs) improve chronic heart failure (HF) outcomes, their potential harms and benefits in acute HF (AHF) is less clear. STUDY QUESTION: We explored the relationship between ACEI or ARB plasma concentrations among patients with AHF with in-hospital change in estimated glomerular filtration rate (eGFR). DATA SOURCES AND STUDY DESIGN: From August 2016-June 2017, patients with AHF prescribed an outpatient ACEI or ARB were enrolled before AHF treatment. All patients were given twice their home dose of diuretic intravenously and received clinical care at the discretion of the medical team. Of 61 patients in the parent study, saved plasma from 34 who were prescribed an outpatient ACEI or ARB was included in this substudy. MEASURES AND OUTCOMES: Liquid chromatography-tandem mass spectrometry was performed to assess ACEI or ARB plasma concentrations before AHF treatment. Change in eGFR was computed using the Chronic Kidney Disease Epidemiology Collaboration equation, which adjusts for age, sex, and race; diuretic dose and enrollment eGFR were used to adjust for HF severity. Multiple linear regression adjusting for enrollment eGFR and diuretic dose was performed to examine the relationship between drug concentration (undetectable/low vs. in/above-range) and in-hospital change in eGFR. RESULTS: Of 34 patients with AHF, median age was 63 years (interquartile range, 58-78 years), 19 (55.9%) were women, median eGFR at enrollment was 55.6 mL/min (interquartile range, 35.2-75.3 mL/min), and for 11 (32.4%), no ACEI or ARB was detectable in plasma. Medication concentrations in- or above-reference range were associated with in-hospital decrease in eGFR of 8.3 mL/min (95% confidence interval, 15.3-1.3 mL/min decrease), after adjusting for enrollment eGFR and diuretic treatment. CONCLUSIONS: Bioanalytical assessment of medication levels may be useful to guide in-hospital ACEI and ARB therapy for patients with AHF.

Polyaniline immobilized on polycaprolactam nanofibers as a sorbent in electrochemically controlled solid-phase microextraction coupled with HPLC for the determination of angiotensin II receptor antagonists in human blood plasma.

In this research, electrospun polycaprolactam nanofibers were collected on a fine stainless steel mesh sheet without a binder, and a layer of conductive polyaniline was chemically deposited on the nanofibers. The polyaniline immobilized on the polycaprolactam nanofibers provided high electrical conductivity, acceptable mechanical stability, and a large surface area. This assembly was then used as a working electrode in electrochemically controlled solid-phase microextraction (EC-SPME), a fast and environmentally friendly method. The polymer layers were characterized by SEM and FTIR techniques. Significant factors affecting the EC-SPME efficiency were investigated, including the desorption conditions, the sorbent used, the pH of the sample solution, the extraction voltage, the extraction time, and the ionic strength. Under the optimum conditions, the limits of detection and quantification for the target analytes were 0.9-1.8 µg L-1 and 3.0-6.1 µg L-1, respectively. The linear dynamic range was 5-2000 µg L-1, with R2 > 0.993. The method was coupled with HPLC analysis and applied to the determination of angiotensin ΙΙ receptor antagonists (ARA-ΙΙs) in human plasma, and relative recoveries of 91.1-104.3% with RSDs of ≤8.3% were obtained.

Functional autoantibodies against Endothelin-1 receptor type A and Angiotensin II receptor type 1 in patients with preeclampsia.

OBJECTIVES: Functional autoantibodies against Angiotensin II Receptor type 1 (AT1-AA) and Endothelin-1 Receptor type A (ETA-AA), which belong to the class of functional autoantibodies, have been discovered in patients with preeclampsia and in rodent models of pregnancy-induced hypertension. The aim of the study was to investigate the expression of these autoantibodies in relation to disease progression. STUDY DESIGN: We included 10 controls and 41 cases defined as patients with gestational-induced hypertension, preeclampsia or HELLP syndrome. MAIN OUTCOME: Serum obtained in the first trimester as well as at the time of disease development were analyzed by means of a biological assay of beating cardiomyocytes. We also measured the protein expression of IL-17A in these samples. RESULTS: 100% of samples from patients with gestational induced hypertension, preeclampsia or HELLP syndrome expressed AT1-AA when they presented with clinical symptoms but not in samples from the first trimester. 44% of samples from patients with severe preeclampsia or HELLP syndrome expressed ETA-AA but only when they presented with clinical symptoms. The controls expressed neither AT1-AA nor ETA-AA. Approximately 40% of patients with severe preeclampsia or HELLP syndrome expressed IL-17A, both at the time of the onset of symptoms and in the first trimester. CONCLUSION: Autoantibodies against the Angiotensin II receptor 1 and Endothelin receptor are developed in relation to pregnancy-induced hypertension and not present at the start of the pregnancy in these patients. IL-17A is increased in some patients with severe preeclampsia, but the expression is not related to the development of clinical symptoms.

Quantification of 21 antihypertensive drugs in serum using UHPLC-MS/MS.

BACKGROUND: Poor drug adherence in hypertensive patients can lead to treatment failure and increased cardiovascular morbidity, as well as increased costs to society. An analytical method based on ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MSMS) was developed and validated for use in routine therapeutic drug monitoring (TDM). The method includes 21 antihypertensive drugs or active metabolites from the groups beta blockers (n=5), calcium antagonists (n=5), angiotensin II receptor antagonists (n=4), angiotensin converting enzyme (ACE) inhibitors (n=3) and diuretics (n = 3), in addition to one α1-selective alpha blocker. METHOD: A 200 µL serum sample was handled automatically using a pipetting robot. Protein precipitation was performed with 600 µL of 1% formic acid in acetonitrile (v:v) and phospholipid removal was carried out using a Waters OSTRO™ 96-well plate. After evaporation and reconstitution the eluent was injected thrice with different inlet and mass spectrometric methods to cover the different physico-chemical properties of the drugs and the variations in therapeutic concentration ranges between drugs. Acquity UPLC BEH C18 (2.1x50mm, 1.7 µm) column equipped with a corresponding pre-column was used for chromatographic separation. For every analyte an isotopically labelled analogue served as internal standard, except for lisinopril where enalaprilat-d5 was used. RESULTS: Accuracies were in the range of -13.7 to 13.2% and intra-day and inter-day precisions in the range of 1.1 to 10.5%. The linearity within the calibration ranges expressed as coefficient of determination was higher than 0.995 for all compounds. Matrix effects and recovery efficiencies were within acceptable limits. The limits of quantitation varied from 0.02 to 10.7 µg/L. The stability of the drugs in serum at different conditions was tested. Diltiazem was not stable at 4-8 °C with up to 23.5 % loss after six days. Degradation of atenolol, irbesartan, bendroflumethiazide, hydrochlorothiazide and diltiazem was observed when stored at 30 °C. The suitability of the method was demonstrated in a routine TDM setting, analysing samples from 127 patients undergoing antihypertensive drug treatment.

Effect of the angiotensin receptor-neprilysin inhibitor sacubitril/valsartan on the pharmacokinetics and pharmacodynamics of a single dose of furosemide.

AIMS: Sacubitril/valsartan is indicated for the treatment of heart failure and reduced ejection fraction (HFrEF). Furosemide, a loop diuretic commonly used for the treatment of HFrEF, may be coadministered with sacubitril/valsartan in clinical practice. The effect of sacubitril/valsartan on the pharmacokinetics and pharmacodynamics of furosemide was evaluated in this open label, two-period, single-sequence study in healthy subjects. METHODS: All subjects (n = 28) received 40 mg oral single-dose furosemide during period 1, followed by a washout of 2 days. In period 2, sacubitril/valsartan 200 mg (97/103 mg) was administered twice daily for 5 days and a single dose of 40 mg furosemide was coadministered on day 6. Serial plasma and urine samples were collected to determine the pharmacokinetics of furosemide and sacubitril/valsartan and the pharmacodynamics of furosemide. The point estimates and the associated 90% confidence intervals for pharmacokinetic parameters were evaluated. RESULTS: Coadministration of furosemide with sacubitril/valsartan decreased the maximum observed plasma concentration (Cmax ) [estimated geometric mean ratio (90% confidence interval): 0.50 (0.44, 0.56)], area under the plasma concentration-time curve (AUC) from time 0 to infinity [0.72 (0.67, 0.77)] and 24-h urinary excretion of furosemide [0.74 (0.69, 0.79)]. When coadministered with sacubitril/valsartan, 0-4-h, 4-8-h and 0-24-h diuresis in response to furosemide was reduced by ~7%, 21% and 0.2%, respectively, while natriuresis was reduced by ~ 28.5%, 7% and 15%, respectively. Post hoc analysis of the pivotal phase III Prospective comparison of ARNI with ACEI to Determine Impact on Global Mortality and morbidity in Heart Failure trial (PARADIGM-HF) indicated that the median furosemide dose was similar at baseline and at the end of the study in the sacubitril/valsartan group. CONCLUSIONS: Sacubitril/valsartan reduced plasma Cmax and AUC and 24-h urinary excretion of furosemide, while not significantly affecting its pharmacodynamic effects in healthy subjects.

Placental transfer and mammary excretion of a novel angiotensin receptor blocker fimasartan in rats.

BACKGROUND: Fimasartan (FMS) is a potent angiotensin receptor blocker for the treatment of mild to moderate hypertension. This study aimed to evaluate the transfer of FMS to fetus and breast milk in rats. METHODS: In order to study the transfer to the fetus and nursing pup, pregnant and nursing maternal rats were administered with FMS by a constant intravenous infusion to reach target plasma concentrations of 200 ng/mL and 100 ng/mL. The concentrations of FMS in plasma, placenta, amniotic fluid, fetus, and milk were determined by a validated LC-MS/MS assay. RESULTS: Upon constant intravenous infusion, the plasma FMS concentration reached the target steady state concentrations (Css = 200 ng/mL and 100 ng/mL) in 24 h. The tissue-to-plasma partition coefficients (Kp) for placenta, amniotic fluid, and milk were obtained based on the observed FMS concentrations in the tissues and Css. The Kp values for all tissues were not different between high (Css = 200 ng/mL) and low (Css = 100 ng/mL) dose groups. While the mean Kp of the placenta was 44.6-59.0 %, the mean Kp was 1.3-1.7 % for the amniotic fluid and 14.9-17.0 % for fetus. The mean Kp of milk was 10.4-15.2 %. CONCLUSIONS: Placental transfer and milk excretion of FMS was relatively lower compared to other angiotensin receptor blockers.

Effect of renal function on the pharmacokinetics of LCZ696 (sacubitril/valsartan), an angiotensin receptor neprilysin inhibitor.

PURPOSE: LCZ696 (sacubitril/valsartan), an angiotensin receptor neprilysin inhibitor, is indicated for chronic heart failure (HF) and reduced ejection fraction (HFrEF) to reduce the risk of cardiovascular death and hospitalization for HF. Following oral administration, LCZ696 provides systemic exposure to valsartan and sacubitril (a prodrug), and its metabolite sacubitrilat (the active neprilysin inhibitor, formerly named as LBQ657), which is eliminated primarily via renal route. Since renal dysfunction is a common comorbidity in patients with HF, two open-label studies assessing the effect of mild, moderate, and severe renal impairment were conducted. METHODS: Patients with mild (N = 8; creatinine clearance [CrCl] 50 to ≤80 mL/min), moderate (N = 8; CrCl 30 to <50 mL/min), and severe (N = 6; CrCl <30 mL/min) renal impairment and matching healthy subjects (CrCl >80 mL/min) for each severity group were enrolled to assess the pharmacokinetics of LCZ696 analytes following administration of LCZ696 400 mg once daily (QD) on days 1 and 5. RESULTS: The steady-state Cmax and AUC0-24h of sacubitril and valsartan were unchanged in patients with renal impairment compared with healthy subjects. However, the steady-state Cmax of sacubitrilat was increased by ∼60 % in patients irrespective of degree of renal impairment; half-life increased from 12 h (in healthy subjects) to 21.1, 23.7, and 38.5 h, respectively; and AUC0-24h was increased 2.10-, 2.24-, and 2.70-fold, respectively, in patients with mild, moderate, and severe renal impairment. CONCLUSION: Renal dysfunction increases exposure to sacubitrilat while not impacting sacubitril and valsartan exposure. LCZ696 was generally well tolerated in patients with renal impairment.

Pharmacodynamic and Pharmacokinetic Profiles of Sacubitril/Valsartan (LCZ696) in Patients with Heart Failure and Reduced Ejection Fraction.

AIMS: Concomitant renin-angiotensin-aldosterone system blockade and natriuretic peptide system enhancement may provide unique therapeutic benefits to patients with heart failure and reduced ejection fraction (HFrEF). This study assessed the pharmacodynamics and pharmacokinetics of LCZ696 in patients with HFrEF. METHODS: This was an open-label, noncontrolled single-sequence study. After a 24-h run-in period, patients (n = 30) with HFrEF (EF ≤ 40%; NYHA class II-IV) received LCZ696 100 mg twice daily (bid) for 7 days and 200 mg bid for 14 days, along with standard treatment for heart failure (HF) (except angiotensin-converting enzyme inhibitors [ACEIs] or angiotensin receptor blockers [ARBs]). RESULTS: On Day 21, significant increases were observed in the plasma biomarkers indicative of neprilysin and RAAS inhibition (ratio-to-baseline: cyclic guanosine monophosphate [cGMP], 1.38; renin concentration and activity, 3.50 and 2.27, respectively; all, P < 0.05). Plasma NT-proBNP levels significantly decreased at all the time points on Days 7 and 21; plasma aldosterone and endothelin-1 levels significantly decreased on Day 21 (all, P < 0.05). Following administration of LCZ696, the Cmax of sacubitril (neprilysin inhibitor prodrug), LBQ657 (active neprilysin inhibitor), and valsartan were reached within 0.5, 2.5, and 2 h. Between 100- and 200-mg doses, the Cmax and AUC0-12 h for sacubitril and LBQ657 were approximately dose-proportional while that of valsartan was less than dose-proportional. CONCLUSIONS: Treatment with LCZ696 for 21 days was well tolerated and resulted in plasma biomarker changes indicative of neprilysin and RAAS inhibition in patients with HF. The pharmacokinetic exposure of the LCZ696 analytes in patients with HF observed in this study is comparable to that observed in the pivotal Phase III study.

Development and validation of a reliable and rapid LC-MS/MS method for simultaneous quantification of sacubitril and valsartan in rat plasma and its application to a pharmacokinetic study.

A selective, sensitive and rapid liquid chromatographic method with electrospray ionization tandem mass spectrometric detection has been developed and validated for simultaneous quantification of sacubitril and valsartan in rat plasma using telmisartan as internal standard (IS). The analytes were extracted by deprotenization of 50 µL of plasma sample using 200 µL of acetonitrile. In a short chromatographic run of 1.50 min run time, separation was achieved on a Hypersil Gold C18 column using a mobile phase composed of 0.1% formic acid in Milli-Q water-0.1% formic acid in acetonitrile in gradient elution mode. The quantification of target compounds was performed in a positive electrospray ionization mode and multiple reaction monitoring. Response was a linear function of concentration in the ranges of 0.5-20,000 ng/mL for both analytes, with r(2) > 0.9997. The intra- and inter-day precision and accuracy results were <15% and acceptable as per US Food and Drug Administration guidelines. Stability of compounds were established in a battery of stability studies, i.e. bench-top, autosampler and long-term storage stability as well as freeze-thaw cycles. The validated method can be used as a routine method to support pharmacokinetic studies. Copyright © 2016 John Wiley & Sons, Ltd.

Absolute bioavailability and pharmacokinetics of the angiotensin II receptor antagonist fimasartan in healthy subjects.

The present study was conducted to determine the absolute bioavailability of fimasartan (FMS; Kanarb(®) ) after the single oral administration of a 60-mg tablet or a single 30-mg intravenous (IV) infusion. This investigation was a randomized, single-dose, open-labeled, two-way crossover study of 16 healthy Korean male subjects. The subjects were divided into two groups (n = 8) and each received either the oral or IV formulation followed by one-week washout period. The Cmax (ng/ml) and AUC∞ (h · ng/ml) following oral and IV administration were 62.4 ± 48.6 and 291.1 ± 121.7; and 683.3 ± 104.3 and 782.3 ± 112.7 (mean ± SD), respectively. The Tmax (h) were 3.0 h (range: 0.5-5.0 h) and 1.0 h (range: 0.8-1.0 h) in the test and reference groups, respectively. The terminal elimination half-lives (t1/2 , h) were similar (5.8 and 5.5 h, respectively) indicating that the route of administration did not influence the absorption or elimination of FMS. The systemic clearance (CL, L/h) and the volume of distribution at steady-state (Vdss , L) were 331.3 ± 444.5 L/h and 403.3 ± 710.4 L following oral administration and 39.1 ± 5.3 L/h and 42.4 ± 25.5 L following IV administration. The absolute bioavailability of the FMS tablet was 18.6%.

Effects of age and sex on the pharmacokinetics of LCZ696, an angiotensin receptor neprilysin inhibitor.

LCZ696, a novel angiotensin receptor neprilysin inhibitor, is in development for the treatment of heart failure. Administration of LCZ696 results in systemic exposure to sacubitril (inactive prodrug of LBQ657), LBQ657 (neprilysin inhibitor), and valsartan (angiotensin II receptor blocker). We investigated the potential effects of age and sex on the pharmacokinetics of LCZ696 analytes (LBQ657 and valsartan) in an open-label, single oral dose (400 mg), parallel-group study in healthy subjects. Among 36 enrolled subjects, there were 19 male and 17 female subjects; 18 subjects were 18-45 years old (young), and 18 subjects were 65 years of age or older (elderly). Compared with young subjects, the AUCinf and T1/2 for LBQ657 were 42% and 30% greater, respectively, in elderly subjects. The Cmax for LBQ657 was similar between age groups. The AUCinf, Cmax, and T1/2 for valsartan were 30%, 24% greater, and 3.35 hours longer, respectively, in the elderly when compared with young subjects. All pharmacokinetic parameters of LCZ696 analytes (LBQ657 and valsartan) were similar between male and female subjects, indicating no effect on the pharmacokinetics of LCZ696 analytes based on sex. Considering the magnitude of change and its clinical significance, dose adjustment based on age or sex is not considered necessary.

Fully Validated Ultra-performance Liquid Chromatography-Tandem Mass Spectrometry Method for the Determination of Fimasartan in Human Plasma.

Fimasartan is a novel angiotensin II receptor blocker with strong anti-hypertensive activity. In this study, a more rapid and sensitive ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method to determine fimasartan in human plasma was developed and fully validated. The quantification of analytes was conducted by MS/MS in a multiple reaction monitoring mode at m/z 502.2 → 207.1 for fimasartan and m/z 526.3 → 207.1 for the internal standard (IS, BR-A-563). The method showed a linear response from 3 to 1000 ng/mL (r > 0.9950). The intra- and inter-day accuracy values were 86.9 - 98.2 and 93.3 - 100.1%, respectively. The intra- and inter-day precision values were 2.0 - 3.1 and 0.8 - 8.0%, respectively. This UPLC-MS/MS method was validated for specificity, linearity, precision, accuracy, recovery, system suitability, and stability, and was found to be acceptable for bioanalytical applications. Finally, this fully validated method was successfully applied to a pharmacokinetic study of fimasartan in healthy volunteers following oral administration.

HPTLC with fluorescence densitometry for simultaneous determination of some angiotensin II receptor blockers in tablets and plasma.

A selective, accurate, precise, and highly sensitive HPTLC assay with reflectance/fluorescence densitometry was developed to separate and quantify some angiotensin II receptor blockers (ARBs), namely, losartan potassium, irbesartan, valsartan, and olmesartan medoxomil, in tablets and plasma. Separation of the target ARBs was performed on precoated silica gel HPTLC plates developed using chloroform-glacial acetic acid (7.5 + 2.5, v/v) mobile phase. The drugs were adequately resolved. After the exposure of the chromatograms to concentrated hydrochloric acid vapor for 10 min, the scanner was set in the reflectance/fluorescence mode with 255 nm excitation wavelength and >400 nm emission filter. The linear regression analysis data for the calibration curves of all studied drugs produced a good linear relationship with correlation coefficients ranging from 0.9991 to 0.9999 over the concentration range of 2-20 ng/band. LOD and LOQ values of all studied drugs ranged from 0.6 to 0.8 and from 1.7 to 2.4 ng/band, respectively. The developed method was successfully applied for analysis of the target ARBs in tablets and spiked human plasma samples with good precision and accuracy.

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.

Pre-treatment with curcumin enhances plasma concentrations of losartan and its metabolite EXP3174 in rats.

The study was carried out in the Wistar rats to investigate the effect of curcumin pre-treatment on the pharmacokinetics of the hypertension-treating drug losartan and its metabolite EXP3174 following single oral administration. In the treatment group, rats were gavaged with losartan 10 mg/kg after repeat oral doses of curcumin (100 mg/kg, for 7 d), while rats in the control group were administrated only with the same dose losartan. The results showed that curcumin significantly increased the plasma concentrations of losartan and its metabolite EXP3174. The present study implicated the existence of herb-drug interaction between curcumin and losartan, and further evaluation of the possible interaction during curcumin administration needs to be considered.

Effect of age on the pharmacokinetics of fimasartan (BR-A-657).

OBJECTIVES: The aim of this study was to compare the pharmacokinetics (PK) and safety of fimasartan (BR-A-657), an angiotensin II receptor antagonist, between healthy young (19 - 45 years) and older (≥ 65 years) male subjects. METHODS: To assess the effect of age on PK and safety, fimasartan was administered as a single 240 mg tablet to 12 young and 10 older male subjects, followed by serial blood sampling over 48 h. Plasma concentrations of fimasartan were analyzed using validated HPLC-MS/MS. Clinical and laboratory adverse events were assessed. RESULTS: After oral administration of 240 mg fimasartan, the mean area under the plasma concentration-time curve from time zero to infinity (AUC(0→∞)) was 2899.0 ng/ml/h in the older, which was significantly greater than in young subjects (1767.4 ng/ml/h; p = 0.03). The geometric mean AUC(0→∞) was 69.4% higher in older than in young subjects. The maximum plasma concentration (C(max)), time to reach C(max) and elimination half-life for fimasartan did not differ significantly between the older and young groups. Importantly, fimasartan was well tolerated during this study. CONCLUSIONS: While some PK parameters were statistically different between the two groups, the effect of age on the PK was modest (e.g., AUC increase < twofold in older subjects).

Chronopharmacology of angiotensin II-receptor blockers in stroke-prone spontaneously hypertensive rats.

Protective effect of valsartan (Val), an angiotensin II (AII)-receptor blocker (ARB), against organ damage is reported to depend on the dosing time in hypertensive patients. Dosing-time-dependent effect of Val on survival of stroke-prone spontaneously hypertensive rats (SHRSP) under a 12-h lighting cycle was examined. Val (4 mg/kg per day) and olmesartan medoxomil (OM) (1 mg/kg per day), another ARB with a slower dissociation from the AII receptor, were given once daily at 2, 8, 14, or 20 HALO (hours after lights on). Dosing-time-dependent differences in plasma drug concentrations and effect on blood pressure (BP) were also evaluated. Survival of SHRSP showed a dosing-time-dependent change during Val therapy, with a peak at 2 HALO and a trough at 14 HALO. OM equally prolonged survival in all groups. The BP-lowering effect persisted for more than 24 h after dosing of Val at 2 HALO and of OM at 2 and 14 HALO, but disappeared at 5.5-h after Val dosing at 14 HALO. Plasma concentrations of Val and OM were higher after dosing at 2 HALO than at 14 HALO. These results suggest that the chronopharmacological phenomenon of Val was partly due to the dosing-time-dependent difference in plasma concentration and subsequent duration of the antihypertensive effect. Slower dissociation of OM from AII receptors might have blunted a potential dosing-time-dependent event.

Quantitation of irbesartan and major proteins in human plasma by mass spectrometry with time-of-flight analyzer.

A simple matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) method was developed to analyze irbesartan in human plasma. Irbesartan is a kind of angiotensin II receptor blocker (ARB) and is used as an antihypertensive drug. MALDI-TOF MS is a rare application for clinical drug analysis in human plasma. After simple micro-liquid-liquid extraction, irbesartan-containing supernatant was spotted on a target plate, mixed with matrix and then detected by MALDI-TOF MS within the clinically therapeutic range. Furthermore, we used cheaper chemical analogues to label the major proteins in human plasma for protein quantitation. After enzyme digestion, peptide mixtures were injected into nanoliquid chromatography (nanoLC) coupled with tandem mass spectrometry (MS-MS). Protein identification could be carried out simultaneously by peptide sequencing and database searching. Chemical analogue labeling method is an alternative way for expensive isotope reagents. Quantity change of proteins before and after administration of irbesartan could be detected by this method. Application of these methods in human plasma demonstrated that these two micro-scale MS methods used for clinical drug monitoring, protein quantitation and identification are successful.

One-year serum albumin is an independent predictor of outcomes in kidney transplant recipients.

OBJECTIVE: This research study was conducted to investigate whether serum albumin levels predict allograft/patient outcomes in the new era of transplant medicine and immunology. METHODS: The association of 1-year post-transplant serum albumin, and patient and graft outcomes was retrospectively analyzed in 500 kidney transplant recipients between 1998 and 2005. Albumin was used as a categorical and a continuous variable in univariate and multivariate Cox regression and Kaplan-Meier survival analyses. RESULTS: The average (±SE) age at transplant was 47 ± 12 years. Patients were followed up for 63.4 ± 28 months after transplant. There were 56 graft losses and 38 patient deaths. In univariate analysis, the following variables were associated with the composite endpoint of patient death or allograft loss: 1-year serum albumin (hazard ratio [HR] = 0.52, P = .0009), 1-year serum albumin <4.0 g/dL (HR = 1.81, P = .02), 1-year serum creatinine (HR = 3.55, P < .00001), angiotensin converting enzyme inhibitors or angiotensin receptor blockers use (HR = 1.61, P = .03), a history of previous transplant (HR = 1.54, P = .04), months of dialysis before transplant (HR = 1.01, P = .00003), type of transplant (deceased donor HR = 1.64, P = .02), and acute rejection (HR = 1.52, P = .0000003). Of these, multivariable Cox regression analyses retained 1-year serum albumin (HR = 1.4, P < .0001), serum creatinine (HR = 2.7, P < .0001), and acute rejection (HR = 1.7, P = .02) as significant predictors of patient/graft loss. CONCLUSION: One-year serum albumin is an independent predictor of poor outcomes in the contemporary era of transplant medicine and immunosuppression. Further studies are needed to separate the role of this biomarker in inflammation and nutrition in kidney transplant recipients.