Evaluation of Drug Dissolution Rate in Co-amorphous and Co-crystal Binary Drug Delivery Systems by Thermodynamic and Kinetic Methods.

In order to better explain and predict the dissolution characteristics of binary drug delivery systems (BDDSs), the dissolution behaviors of co-crystal (CC) and co-amorphous (CA) systems of sacubitril (SCB) and valsartan (VST) were evaluated in vitro and in vivo by thermodynamic and kinetic methods. The CCs of SCB and VST were prepared into a CA state through rotary evaporation. Solid-state properties were systematically evaluated. Herein, based on the results from previous studies of single-phase systems, we used thermodynamic methods to evaluate the increase in drug dissolution rate after BDDSs change from the crystalline to the amorphous state. After comparing the predicted and measured dissolution rate enhancement of the CC and CA systems, this paper attempts to explain the dissolution rate characteristics of the BDDSs. We then evaluated the bioavailability of two BDDSs in beagle dogs to confirm that there was no discrepancy in vivo with the results obtained in vitro. The results exhibited that there is strong intermolecular interaction between SCB and VST and good physical stability for the CA system. Compared with the CC, the bioavailability of SCB and VST in the CA system increased by 313.9% and 130.5%, respectively. The predicted dissolution rate ratio between CC and CA systems and their actual intrinsic dissolution rates differed by only a factor of 2.5, demonstrating the good correlation between the predicted and measured values. In the future, this method could be expanded to a variety of new samples and exciting drug prospects.

Pharmacogenetic study of ACE, AGT, CYP11B1, CYP11B2 and eNOS gene variants in hypertensive patients from Faisalabad, Pakistan.

OBJECTIVE: To investigate the association of genetic variants of renin angiotensin aldosterone system, endothelial nitric oxide synthase and 11-beta-hydroxylase genes, and the drug efficacy of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker. METHODS: This two time-point study was conducted from April to November 2016 at Allied Hospital, Faisalabad and National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, and comprised of hypertensive patients taking angiotensin-converting enzyme inhibitor and angiotensin receptor blocker who were followed up for 12 weeks. Baseline and follow-up clinical and biochemical parameters were measured for all patients. Total 11 polymorphisms were genotyped by polymerase chain reaction, polymerase chain reaction-restriction fragment length polymorphism and amplification-refractory mutation system-polymerase chain reaction assays. Data was divided into baseline and follow-up groups, while the latter group was further divided into responding and non-responding subgroups on the basis of patient response to angiotensin-converting enzyme inhibitor and angiotensin receptor blocker drugs. Data was analysed using SPSS 20. RESULTS: Of the 45 patients, 25(55.5%) were females and 20(44.5%) were males. There was a significant reduction in the systolic blood pressure (p=0.004) and low-density lipoprotein cholesterol (p<0.001) from the baseline to the follow-up. Systolic blood pressure was significantly reduced in the responding group (p=0.003), while diastolic blood pressure (p=0.121) was not significantly different. There was no effect of angiotensin-converting enzyme, angiotensinogen, 11-beta-hydroxylase, aldosterone synthase and endothelial nitric oxide synthase gene polymorphisms on angiotensin converting enzyme inhibitor and angiotensin receptor blocker efficacy. CONCLUSIONS: Inter-individual response to angiotensin converting enzyme inhibitor and angiotensin receptor blocker was found to be independent of genetic polymorphisms in renin angiotensin aldosterone system, endothelial nitric oxide synthase and 11-beta-hydroxylase genes.

Antihypertensive Agents in the Dialysis Patient.

PURPOSE OF REVIEW: Hypertension and antihypertensive drug utilization are remarkably prevalent in ESRD patients. Management of blood pressure elevation in this population is complicated by many factors, including a multidimensional etiology, challenges in obtaining accurate and appropriately timed blood pressure measurements, highly specific drug dosing requirements, and a paucity of outcomes-based evidence to guide management decisions. The purpose of this review is to summarize and apply knowledge from existing clinical trials to enhance safe and effective use of antihypertensive agents in dialysis patients. RECENT FINDINGS: Two meta-analyses have established the benefit of antihypertensive therapy in ESRD. Data supporting the use of one antihypertensive class over another is less robust; however, beta-blockers have more clearly demonstrated improved cardiovascular outcomes in prospective randomized trials. Interdialytic home blood pressure monitoring has been demonstrated to be better associated with cardiovascular outcomes than clinic pre- or post-dialysis readings and should ideally be considered as a routine part of blood pressure management in this population. As data from small trials provides limited guidance for the management of hypertension in ESRD, more research is needed to guide medication selection and utilization. Specifically, large prospective randomized trails comparing cardiovascular outcomes of various medication classes and differing blood pressure targets are needed.

Sacubitril/Valsartan and Mexiletine: A Proarrhythmic Combination?

The uptake of sacubitril/valsartan since the PARADIGM study confirmed its beneficial effects on outcomes over enalapril in chronic systolic heart failure has inevitably led to potential interactions with co-prescribed medications in real-world patients. We report two cases that raise the possibility of an interaction between sacubitril/valsartan and the class Ib anti-arrhythmic mexiletine resulting in proarrhythmic effects. We discuss the pharmacokinetics of both agents and posit potential mechanistic interactions that suggest caution should be used and careful monitoring for (ventricular) arrhythmias applied in patients receiving sacubitril/valsartan and mexiletine.

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.

The effect of angiotensin receptor neprilysin inhibitor, sacubitril/valsartan, on central nervous system amyloid-ß concentrations and clearance in the cynomolgus monkey.

Sacubitril/valsartan (LCZ696) is the first angiotensin receptor neprilysin inhibitor approved to reduce cardiovascular mortality and hospitalization in patients with heart failure with reduced ejection fraction. As neprilysin (NEP) is one of several enzymes known to degrade amyloid-ß (Aß), there is a theoretical risk of Aß accumulation following long-term NEP inhibition. The primary objective of this study was to evaluate the potential effects of sacubitril/valsartan on central nervous system clearance of Aß isoforms in cynomolgus monkeys using the sensitive Stable Isotope Labeling Kinetics (SILK™)-Aß methodology. The in vitro selectivity of valsartan, sacubitril, and its active metabolite sacubitrilat was established; sacubitrilat did not inhibit other human Aß-degrading metalloproteases. In a 2-week study, sacubitril/valsartan (50mg/kg/day) or vehicle was orally administered to female cynomolgus monkeys in conjunction with SILK™-Aß. Despite low cerebrospinal fluid (CSF) and brain penetration, CSF exposure to sacubitril was sufficient to inhibit NEP and resulted in an increase in the elimination half-life of Aß1-42 (65.3%; p=0.026), Aß1-40 (35.2%; p=0.04) and Aßtotal (29.8%; p=0.04) acutely; this returned to normal as expected with repeated dosing for 15days. CSF concentrations of newly generated Aß (AUC(0-24h)) indicated elevations in the more aggregable form Aß1-42 on day 1 (20.4%; p=0.039) and day 15 (34.7%; p=0.0003) and in shorter forms Aß1-40 (23.4%; p=0.009), Aß1-38 (64.1%; p=0.0001) and Aßtotal (50.45%; p=0.00002) on day 15. However, there were no elevations in any Aß isoforms in the brains of these monkeys on day 16. In a second study cynomolgus monkeys were administered sacubitril/valsartan (300mg/kg) or vehicle control for 39weeks; no microscopic brain changes or Aß deposition, as assessed by immunohistochemical staining, were present. Further clinical studies are planned to address the relevance of these findings.

The effect of LCZ696 (sacubitril/valsartan) on amyloid-ß concentrations in cerebrospinal fluid in healthy subjects.

AIMS: LCZ696 (angiotensin receptor neprilysin inhibitor) is a novel drug developed for the treatment of heart failure with reduced ejection fraction. Neprilysin is one of multiple enzymes degrading amyloid-ß (Aß). Its inhibition may increase Aß levels. The potential exists that treatment of LCZ696, through the inhibition of neprilysin by LBQ657 (an LCZ696 metabolite), may result in accumulation of Aß. The aim of this study was to assess the blood-brain-barrier penetration of LBQ657 and the potential effects of LCZ696 on cerebrospinal fluid (CSF) concentrations of Aß isoforms in healthy human volunteers. METHODS: In a double-blind, randomized, parallel group, placebo-controlled study, healthy subjects received once daily LCZ696 (400 mg, n = 21) or placebo (n = 22) for 14 days. RESULTS: LCZ696 had no significant effect on CSF AUEC(0,36 h) of the aggregable Aß species 1-42 or 1-40 compared with placebo (estimated treatment ratios 0.98 [95% CI 0.73, 1.34; P = 0.919] and 1.05 [95% CI 0.82, 1.34; P = 0.702], respectively). A 42% increase in CSF AUEC(0,36 h) of soluble Aß 1-38 was observed (estimated treatment ratio 1.42 [95% CI 1.05, 1.91; P = 0.023]). CSF levels of LBQ657 and CSF Aß 1-42, 1-40, and 1-38 concentrations were not related (r(2) values 0.022, 0.010, and 0.008, respectively). CONCLUSIONS: LCZ696 did not cause changes in CSF levels of aggregable Aß isoforms (1-42 and 1-40) compared with placebo, despite achieving CSF concentrations of LBQ657 sufficient to inhibit neprilysin. The clinical relevance of the increase in soluble CSF Aß 1-38 is currently unknown.

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.

Single therapeutic and supratherapeutic doses of sacubitril/valsartan (LCZ696) do not affect cardiac repolarization.

PURPOSE: Sacubitril/valsartan (LCZ696) is a first-in-class angiotensin receptor neprilysin inhibitor (ARNI) indicated to reduce the risk of cardiovascular death and hospitalization for heart failure in patients with chronic heart failure (NYHA class II-IV) and reduced ejection fraction. This study was aimed to evaluate the effect of single oral therapeutic (400 mg) and supratherapeutic (1200 mg) doses of LCZ696 on cardiac repolarization. METHOD: This randomized double-blind crossover study in healthy male subjects compared the effect of therapeutic and supratherapeutic doses of LCZ696 with placebo and moxifloxacin 400 mg (open-label treatment) as positive control. The primary assessment was mean baseline- and placebo-corrected QTcF (∆∆QTcF; Fridericia correction). Additional assessments included the ∆∆QTcB (Bazett's correction), PR interval, QRS duration, heart rate (HR), LCZ696 pharmacokinetics, pharmacokinetic/pharmacodynamic relationships, and safety. RESULTS: Of the 84 subjects enrolled, 81 completed the study. The maximum upper bound of the two-sided 90 % confidence interval for ∆∆QTcF for LCZ696 400 mg and 1200 mg were <10 ms, and assay sensitivity was confirmed with moxifloxacin. No relevant treatment-emergent changes were observed in any of the ECG-derived parameters with LCZ696 or placebo, and the incidence of adverse events was comparable among the treatment groups. CONCLUSION: Single therapeutic and supratherapeutic doses of LCZ696 did not affect cardiac repolarization as defined by the E14 ICH guidelines.

Effect of food on the oral bioavailability of the angiotensin receptor - neprilysin inhibitor sacubitril/valsartan (LCZ696) in healthy subjects
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OBJECTIVE: Sacubitril/valsartan (LCZ696) provides a novel therapeutic approach of neurohormonal modulation in heart failure via simultaneous inhibition of neprilysin and blockade of the angiotensin II type-1 receptor. This study was conducted to evaluate the effect of food on the oral bioavailability of LCZ696 analytes. MATERIALS AND METHODS: This was an open-label, randomized, 3-period crossover study in healthy subjects. Eligible subjects (N = 36) were randomized to 6 treatment sequences, each comprising 3 treatment periods during which subjects received a single oral dose of 400 mg LCZ696 under fasting condition and following a low- and high-fat meal. RESULTS: Following administration of LCZ696 after low- and high-fat meals, the mean Cmax of sacubitril and sacubitrilat (the active neprilysin inhibitor) decreased by 42 - 54% and 19 - 28%, respectively, while the tmax values increased. However, systemic exposure (AUCinf and AUClast) of sacubitril was slightly decreased (by 16% with low-fat meal) and that of sacubitrilat was unchanged in the presence of food. For valsartan, the Cmax decreased by ~ 40% when LCZ696 was administered after low- and high-fat meals. The systemic exposure of valsartan decreased by ~ 33% with a low-fat meal; however, it was unchanged with a high-fat meal. LCZ696 was generally safe and well tolerated in healthy subjects when administered under fasting or fed condition. CONCLUSION: Overall, administration of LCZ696 with meals decreased the rate and extent of absorption of sacubitril with little impact on the systemic exposure to sacubitrilat, its active metabolite. The systemic exposure to valsartan was decreased in the presence of food.
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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.

A case of lithium intoxication induced by an antihypertensive angiotensin 1 subtype-specific angiotensin II receptor blocker in an elderly patient with bipolar disorder and hypertension.

Lithium carbonate is considered to be a first-line treatment for bipolar disorder; however, this drug has a narrow therapeutic window, and lithium intoxication is commonly induced by various drugs interaction and situations. We herein report a case of lithium intoxication induced by the administration of an antihypertensive agent targeting the angiotensin 1 (AT1) subtype of the angiotensin II receptor in a 65-year-old woman with a 40-year history of bipolar disorder type 1, and 1-year history of essential hypertension. Her bipolar disorder had been well-controlled with 600 mg/day of lithium carbonate for more than 10 years. She was later diagnosed with hypertension and the AT1 receptor blocker, azilsartan was thereafter administrated on a daily basis. After 3 weeks of azilsartan administration, she presented with progressive action tremor and showed a gradual deterioration of her physical state. Four months after the start of azilsartan administration, she presented with alternating episodes of diarrhea and constipation. Two weeks before admission to our hospital, she presented with mild consciousness disturbances, myoclonus, truncal ataxia, and appetite loss. She was diagnosed to have lithium intoxication based on an elevated serum lithium concentration of 3.28 mEq/l.It is therefore important to evaluate the serum lithium concentration after the administration of antihypertensive agents, and consider lithium-antihypertensive agent interactions when selecting antihypertensive agents in elderly patients receiving long-term lithium carbonate treatment.

Differences in 24-h blood pressure profile of Japanese hypertensive patients under ARB treatment.

Blood pressure (BP) control throughout the entire day is recommended for cardiovascular protection. Angiotensin-II receptor blockers (ARBs) are widely used in hypertensive patients because of beneficial class effects. It is uncertain, however, whether are there any differences in 24-h BP profiles among ARBs. We examined ambulatory blood pressure monitoring (ABPM) among 211 Japanese hypertensive patients (age, 69.4 ± 9.6 years; female, 59.2%) under treatment with five different ARBs. Patients were divided into five groups according to ARBs prescribed. Patient backgrounds were almost identical in all the groups and there were no differences in office, 24-h and daytime BP; however, nighttime BP with olmesartan was significantly lower than with other ARBs. Office BPs with candesartan and telmisartan, but not other ARBs, correlated well with 24-h BP (p < 0.01). Also, there were higher correlations between daytime and nighttime BP with candesartan and telmisartan. In all patients, pulse pressure with office BP was significantly correlated with ambulatory arterial stiffness index (p = 0.001) and fluctuation of systolic BP on ABPM (p = 0.002). In conclusion, different ARB treatments produced meaningful differences in 24-h profiles.

Evaluation of the relationship between sex, polymorphisms in CYP2C8 and CYP2C9, and pharmacokinetics of angiotensin receptor blockers.

Angiotensin II receptor blockers (ARBs) are used to treat hypertension. Most ARBs are metabolized by CYP2C9. The aim of this study is to evaluate the possible association between sex, polymorphisms in the CYP2C8 and CYP2C9 genes, and the pharmacokinetics of losartan, valsartan, candesartan, and telmisartan. The study population comprised 246 healthy volunteers from seven single-dose clinical trials: 64 from two candesartan studies, 43 from a telmisartan study, 36 from a losartan study, and 103 from three valsartan studies. DNA was extracted from blood samples and single-nucleotide polymorphisms in the CYP2C8 (CYP2C8*2, CYP2C8*3, CYP2C8*4, CYP2C8*5) and CYP2C9 (CYP2C9*2, CYP2C9*3) genes were evaluated using real-time polymerase chain reaction. Sex only affected telmisartan pharmacokinetics, since women showed a higher telmisartan C(max) than men (590.5 ± 75.8 ng/ml versus 282.1 ± 30.8 ng/ml; P ≤ 0.01). CYP2C9 variants were associated only with losartan pharmacokinetics: the half-life of losartan was higher in CYP2C9*3 allele carriers (3.1 ± 0.4 hours) than in volunteers with the wild-type genotype (2.3 ± 0.1 hours) (P ≤ 0.05). CYP2C8 polymorphisms were associated only with valsartan pharmacokinetics, since *2 allele carriers showed faster clearance (1.07 ± 0.57 l/h·kg) than those with the wild-type genotype (0.48 ± 0.72 l/h·kg; P ≤ 0.01) and carriers of the *3 allele (0.35 ± 0.49 l/h·kg; P ≤ 0.001). These results suggest that genotypes for CYP2C9 and CYP2C8 are relevant to the pharmacokinetics of losartan and valsartan, respectively, but not the pharmacokinetics of candesartan or telmisartan.

Estimation in AB/BA crossover trials with application to bioequivalence studies with incomplete and complete data designs.

Crossover studies are frequently used in clinical research as they allow within-subject comparisons instead of the between-subject evaluation of parallel group designs. Estimation of interesting parameters from such designs is, however, not trivial. We provide three methods for estimating treatment effects and associated standard errors from an AB/BA crossover trial. Assuming at least asymptotic normality, we can obtain the confidence intervals for single parameters as well as for differences or ratios of treatment effects. The latter is particularly useful in a pharmacokinetic context to establish bioequivalence using area under the concentration versus time curves (AUCs). In this work, we will illustrate how Fieller-type confidence intervals can be constructed for the ratio of AUCs estimated using a noncompartmental approach in a sparse sampling setting from a two-treatment, two-period, two-sequence crossover trial. In particular, we will discuss a flexible batch design, which includes traditional serial sampling and complete data designs as special cases. Via simulation, we show that the proposed intervals have nominal coverage and keep the type I error even for small sample sizes. Moreover, we illustrate the methodology in a real data example.

In vivo biliary clearance should be predicted by intrinsic biliary clearance in sandwich-cultured hepatocytes.

It has been reported that in vivo biliary clearance can be predicted using sandwich-cultured rat and human hepatocytes. The predicted apparent biliary clearance (CL(bile, app)) from sandwich- cultured rat hepatocytes (SCRH) based on medium concentrations correlates to in vivo CL(bile, app) based on plasma concentrations of angiotensin II receptor blockers (ARBs), HMG-CoA reductase inhibitors (statins), ß-lactam antibiotics, and topotecan. However, the predicted biliary clearance from SCRH was 7- to 300-fold lower than in vivo biliary clearance. We speculated that the process of biliary excretion might not have been evaluated using sandwich-cultured hepatocytes. To evaluate this issue, intrinsic biliary clearance (CL(bile, int)) based on intracellular compound concentrations was evaluated to investigate the in vitro-in vivo correlation of this process among ARBs, statins, ß-lactam antibiotics, and topotecan. Intrinsic biliary clearance in SCRH correlated to in vivo values obtained by constant intravenous infusion of six compounds, but not rosuvastatin and cefmetazole, to rats. Moreover, differences between SCRH and in vivo CL(bile, int) (0.7-6-fold) were much smaller than those of CL(bile, app) (7-300-fold). Therefore, in vivo CL(bile, int) is more accurately reflected using SCRH than CL(bile, app). In conclusion, to predict in vivo biliary clearance more accurately, CL(bile, int) should be evaluated instead of CL(bile, app) between SCRH and in vivo.

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.

The evolution of the OATP hepatic uptake transport protein family in DMPK sciences: from obscure liver transporters to key determinants of hepatobiliary clearance.

Over the last two decades the impact on drug pharmacokinetics of the organic anion transporting polypeptides (OATPs: OATP-1B1, 1B3 and 2B1), expressed on the sinusoidal membrane of the hepatocyte, has been increasingly recognized. OATP-mediated uptake into the hepatocyte coupled with subsequent excretion into bile via efflux proteins, such as MRP2, is often referred to as hepatobiliary excretion. OATP transporter proteins can impact some drugs in several ways including pharmacokinetic variability, pharmacodynamic response and drug-drug interactions (DDIs). The impact of transporter mediated hepatic clearance is illustrated with case examples, from the literature and also from the Pfizer portfolio. The currently available in vitro techniques to study the hepatic transporter proteins involved in the hepatobiliary clearance of drugs are reviewed herein along with recent advances in using these in vitro data to predict the human clearance of compounds recognized by hepatic uptake transporters.

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.

[Hypertension, obesity, erectile dysfunction. What kind of drug to choose].

Hypertension is one of the most common cardiovascular diseases. The development and progression of hypertension is associated with prolonged hyper activation of the renin-angiotensin-aldosterone system. ACE inhibitors and angiotensin receptor blockers (ARBs) are highly effective medicines and are widely used in the treatment of cardiovascular diseases: hypertension, congestive heart failure, coronary heart disease. The main pharmacological effects of ACE inhibitors and ARBs are hypotensive, neurohumoral, antiproliferative, cardio- and nefroprotective functions, as well as constantly improving endothelial function. In accordance with the article, hypertensive effectiveness, tolerability and organ-protective properties of valsartan are noticeable among patients with hypertension, obesity and erectile dysfunction, taking this medicine.