Elucidating nonlinear pharmacokinetics of telmisartan: Integration of target-mediated drug disposition and OATP1B3-mediated hepatic uptake in a physiologically based model.

Telmisartan, a selective inhibitor of angiotensin II receptor type 1 (AT1), demonstrates nonlinear pharmacokinetics (PK) when orally administered in ascending doses to healthy volunteers, but the underlying mechanisms remain unclear. This study presents a physiologically based pharmacokinetic model integrated with target-mediated drug disposition (TMDD-PBPK model) to explore the mechanism of its nonlinear PK. We employed the Cluster-Gauss Newton method for top-down analysis, estimating the in vivo Km,OATP1B3 (Michaelis-Menten constant for telmisartan hepatic uptake via Organic Anion Transporting Polypeptide 1B3) to be 2.0-5.7 nM. This range is significantly lower than the reported in vitro value of 810 nM, obtained in 0.3% human serum albumin (HSA) conditions. Further validation was achieved through in vitro assessment in plated human hepatocytes with 4.5% HSA, showing a Km of 4.5 nM. These results underscore the importance of albumin-mediated uptake effect for the hepatic uptake of telmisartan. Our TMDD-PBPK model, developed through a "middle-out" approach, underwent sensitivity analysis to identify key factors in the nonlinear PK of telmisartan. We found that the nonlinearity in the area under the concentration-time curve (AUC) and/or maximum concentration (Cmax) of telmisartan is sensitive to Km,OATP1B3 across all dosages. Additionally, the dissociation constant (Kd) for telmisartan binding to the AT1 receptor, along with its receptor abundance, notably influences PK at lower doses (below 20 mg). In conclusion, the nonlinear PK of telmisartan appears primarily driven by hepatic uptake saturation across all dose ranges and by AT1-receptor binding saturation, notably at lower doses.

Pharmacokinetic Comparison of a Fixed-Dose Combination of Candesartan Cilexetil/Amlodipine/Atorvastatin Versus Co-administration of Individual Formulations in Healthy Participants.

INTRODUCTION: Fixed-dose combinations (FDCs) of angiotensin II receptor blockers, calcium channel blockers, and statins are conventional therapeutic interventions prescribed for cardiovascular diseases. This study aimed at drawing a comparison between the pharmacokinetics and safety of an FDC and the corresponding individual formulations in healthy subjects. METHODS: A randomized, open-label, single-dose, three-sequence, three-period, partially repeated crossover study was conducted with a cohort of healthy volunteers. A 14-day washout period was maintained between each of the three periods. In this study, candesartan cilexetil, amlodipine, and atorvastatin was administered orally as FDCs of 16/10/40 mg in study 1 and 16/5/20 mg in study 2. The maximum plasma concentration (Cmax) and area under the plasma concentration-time curve from time zero to the time of the last quantifiable concentration (AUClast) of candesartan, amlodipine, and atorvastatin were estimated as the geometric mean ratios (GMRs) and 90% confidence intervals (CIs) of the FDC to individual formulations. If the within-subject coefficient of variation (CVwr) of Cmax was greater than 0.3, the bioequivalence (BE) range calculated using the reference-scaled average bioequivalence was used to assess whether the 90% CI was within the BE range. RESULTS: The GMRs (90% CIs) for the AUClast for candesartan and amlodipine were 0.9612 (0.9158-1.0089)/0.9965 (0.9550-1.0397) and 1.0033 (0.9800-1.0271)/1.0067 (0.9798-1.0344), and the GMRs (90% CIs) for Cmax were 0.9600 (0.8953-1.0294)/0.9851 (0.9368-1.0359) and 1.0198 (0.9950-1.0453)/1.0003 (0.9694-1.0321) in studies 1 and 2, respectively. The extended BE ranges calculated from the CVwr of the Cmax of atorvastatin were 0.7814-1.2797 and 0.7415-1.3485, respectively. The GMRs (90% CIs) for the AUClast of atorvastatin were 1.0532 (1.0082-1.1003)/1.0252 (0.9841-1.0680), and the GMRs (90% CIs) for Cmax were 1.0630 (0.9418-1.1997)/0.9888 (0.8792-1.1120) in studies 1 and 2, respectively. CONCLUSION: The Cmax and AUClast values of candesartan cilexetil/amlodipine/atorvastatin 16/10/40 mg and 16/5/20 mg, respectively, were within the BE ranges. There were no clinically significant differences in safety between the two formulations. TRIAL REGISTRATION: ClinicalTrials.gov identifier, study 1: NCT04478097; study 2: NCT04627207.

Conversion of Olmesartan to Olmesartan Medoxomil, A Prodrug that Improves Intestinal Absorption, Confers Substrate Recognition by OATP2B1.

PURPOSE: Olmesartan medoxomil (olmesartan-MX), an ester-type prodrug of the angiotensin II receptor blocker (ARB) olmesartan, is predominantly anionic at intestinal pH. Human organic anion transporting polypeptide 2B1 (OATP2B1) is expressed in the small intestine and is involved in the absorption of various acidic drugs. This study was designed to test the hypothesis that OATP2B1-mediated uptake contributes to the enhanced intestinal absorption of olmesartan-MX, even though olmesartan itself is not a substrate of OATP2B1. METHODS: Tetracycline-inducible human OATP2B1- and rat Oatp2b1-overexpressing HEK 293 cell lines (hOATP2B1/T-REx-293 and rOatp2b1/T-REx-293, respectively) were established to characterize OATP2B1-mediated uptake. Rat jejunal permeability was measured using Ussing chambers. ARBs were quantified by liquid chromatography-tandem mass spectrometry. RESULTS: Significant olmesartan-MX uptake was observed in hOATP2B1/T-REx-293 and rOatp2b1/T-REx-293 cells, whereas olmesartan uptake was undetectable or much lower than olmesartan-MX uptake, respectively. Furthermore, olmesartan-MX exhibited several-fold higher uptake in Caco-2 cells and greater permeability in rat jejunum compared to olmesartan. Olmesartan-MX uptake in hOATP2B1/T-REx-293 cells and in Caco-2 cells was significantly decreased by OATP2B1 substrates/inhibitors such as 1 mM estrone-3-sulfate, 100 µM rifamycin SV, and 100 µM fluvastatin. Rat Oatp2b1-mediated uptake and rat jejunal permeability of olmesartan-MX were significantly decreased by 50 µM naringin, an OATP2B1 inhibitor. Oral administration of olmesartan-MX with 50 µM naringin to rats significantly reduced the area under the plasma concentration-time curve of olmesartan to 76.9%. CONCLUSION: Olmesartan-MX is a substrate for OATP2B1, and the naringin-sensitive transport system contributes to the improved intestinal absorption of olmesartan-MX compared with its parent drug, olmesartan.

Olmesartan niosomes ameliorates the Indomethacin-induced gastric ulcer in rats: Insights on MAPK and Nrf2/HO-1 signaling pathway.

AIMS: Gastric ulcer is a continuous worldwide threat that inquires protective agents. Olmesartan (OLM) has potent anti-oxidant and anti-inflammatory characters, yet having limited bioavailability. We targeted the gastro-protective potential and probable mechanism of OLM and its niosomal form against indomethacin (IND) induced-gastric ulcer in rats. MAIN METHODS: we prepared OLM niosomes (OLM-NIO) with different surfactant: cholesterol molar ratios. We evaluated particle size, zeta-potential, polydispersity, and entrapment efficiency. In-vitro release study, Fourier transform infrared spectroscopy, differential scanning calorimetry, and transmission electron microscopy were performed for selected niosomes. In-vivo, we used oral Omeprazole (30 mg/kg), OLM or OLM-NIO (10 mg/kg) for 3 days before IND (25 mg/kg) ingestion. We assessed gastric lesions, oxidative and inflammatory markers. KEY FINDINGS: OLM-NIO prepared with span 60:cholesterol ratio (1:1) showed high entrapment efficiency 93 ± 2%, small particle size 159.3 ± 6.8 nm, low polydispersity 0.229 ± 0.009, and high zeta-potential -35.3 ± 1.2 mV, with sustained release mechanism by release data. In-vivo macroscopical and histological results showed gastro-protective effects of OLM pretreatment, which improved oxidative stress parameters and enhanced the gastric mucosal cyclooxygenase-1 (COX-1) and prostaglandin E2 (PGE2) contents. OLM pretreatment suppressed interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) contents and translocation of p38 mitogen-activated protein kinase (p38-MAPK). Besides, OLM substantially promoted the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) protective pathway. OLM-NIO furtherly improved all previous outcomes. SIGNIFICANCE: We explored OLM anti-ulcerative effects, implicating oxidative stress and inflammation improvement, mediated by the Nrf2/HO-1 signaling pathway and p38-MAPK translocation. Meanwhile, the more bioavailable OLM-NIO achieved better gastro-protective effects compared to conventional OLM form.

Physiologically based pharmacokinetic modeling of candesartan related to CYP2C9 genetic polymorphism in adult and pediatric patients.

Candesartan cilexetil is an angiotensin II receptor blocker and it is widely used to treat hypertension and heart failure. This drug is a prodrug that rapidly converts to candesartan after oral administration. Candesartan is metabolized by cytochrome P450 2C9 (CYP2C9) enzyme or uridine diphosphate glucurinosyltransferase 1A3, or excreted in an unchanged form through urine, biliary tract and feces. We investigated the effect of genetic polymorphism of CYP2C9 enzyme on drug pharmacokinetics using physiologically based pharmacokinetic (PBPK) modeling. In addition, by introducing the age and ethnicity into the model, we developed a model that can propose an appropriate dosage regimen taking into account the individual characteristics of each patient. To evaluate the suitability of the model, the results of a clinical trial on twenty-two healthy Korean subjects and their CYP2C9 genetic polymorphism data was applied. In this study, PK-Sim® was used to develop the PBPK model of candesartan.

Pharmacokinetic study on the interaction between succinic acid and irbesartan in rats and its potential mechanism.

CONTEXT: Succinic acid and irbesartan are commonly used drugs in cardiovascular disease treatment. The interaction might occur during their co-administration, which was still unclear. OBJECTIVE: To reveal the effect of succinic acid on the metabolism of irbesartan and its potential mechanism. MATERIALS AND METHODS: The Sprague-Dawley rats (n = 6) were treated with a single dose of 30 mg/kg irbesartan (control) or the co-administration with the pre-treatment of 200 mg/kg succinic acid for 7 d. The effect of succinic acid on the metabolic stability and the activity of CYP2C9 was evaluated in rat liver microsomes. RESULTS: Succinic acid increased the AUC (5328.71 ± 959.31 µg/L × h vs. 3340.23 ± 737.75 µg/L × h) and prolonged the half-life of irbesartan (from 12.79 ± 0.73 h to 20.59 ± 6.35 h). The Tmax (2.83 ± 0.75 h vs. 3.83 ± 1.10 h) and clearance rate (3.46 ± 1.13 L/h/kg vs. 6.91 ± 1.65 L/h/kg) of irbesartan was reduced by succinic acid. Consistently, succinic acid improved the metabolic stability (half-life from 23.32 ± 3.46 to 27.35 ± 2.15 min, intrinsic clearance rate from 59.43 ± 6.12 to 50.68 ± 5.64 µL/min/mg protein). Succinic acid was also found to inhibit the activity of CYP2C9 with the IC50 value of 13.87 µM. DISCUSSION AND CONCLUSIONS: Succinic acid increased the system exposure of irbesartan via inhibiting CYP2C9. The experiment design of this study also provides a reference for the further validation of this interaction in humans.

Pharmacokinetic Interaction Among Ezetimibe, Rosuvastatin, and Telmisartan.

To evaluate the pharmacokinetic interactions among rosuvastatin, ezetimibe, and telmisartan, a randomized, open-label, 3-period, 6-sequence crossover study was conducted in healthy subjects. Subjects received one of the following treatments once daily for 7 days in each period with a 1-week washout: a fixed-dose combination of ezetimibe/rosuvastatin 10/20 mg, telmisartan 80 mg, combination therapy of ezetimibe/rosuvastatin 10/20 mg, or telmisartan 80 mg. Blood samples were collected up to 24 hours postdose at steady state. Geometric mean ratios (GMRs) and their 90% confidence intervals (CIs) of the combination therapy to monotherapy for the maximum plasma concentration (Cmax,ss ), and the area under the time-concentration curve within a dosing interval at steady state (AUCtau,ss ) were estimated. Among the 36 randomized subjects, 31 subjects completed the study. The GMRs and 90%CIs of Cmax,ss and AUCtau,ss of total ezetimibe were not significantly altered. The Cmax,ss of free ezetimibe was increased (GMR, 1.85; 90%CI, 1.56-2.19) but not for the AUCtau,ss (GMR, 1.16; 90%CI, 1.06-1.26). Similarly, the Cmax,ss of rosuvastatin was increased (GMR, 2.13; 90%CI, 1.88-2.43) without a change in the AUCtau,ss (GMR, 1.09; 90%CI, 1.03-1.15). The Cmax,ss (GMR, 1.16; 90%CI, 1.01-1.32) and AUCtau,ss (GMR, 1.26; 90%CI, 1.17-1.37) of telmisartan were slightly increased. Considering the therapeutic range of the components, the interaction would have limited clinical impact.

Molecular Dynamics Protocols for the Study of Cyclodextrin Drug Delivery Systems.

Hypertension treatment is a current therapeutic priority as there is a constantly increasing part of the population that suffers from this risk factor, which may lead to cardiovascular and encephalic episodes and eventually to death. A number of marketed medicines consist of active ingredients that may be relatively potent; however, there is plenty of room to enhance their pharmacological profile and therapeutic index by improving specific physicochemical properties. In this work, we focus on a class of blood pressure regulators, called sartans, and we present the computational scheme for the pharmacological improvement of irbesartan (IRB) as a representative example. IRB has been shown to exert increased pharmacological action compared with other sartans, but it appears to be highly lipophilic and violates Lipinski rule (MLogP >4.15). To circumvent this drawback, proper hydrophilic molecules, such as cyclodextrins, can be used as drug carriers. This chapter describes the combinatory use of computational methods, namely molecular docking, quantum mechanics, molecular dynamics, and free energy calculations, to study the interactions and the energetic contributions that govern the IRB:cyclodextrin association. We provide a detailed computational protocol, which aims to assist the improvement of the pharmacological properties of sartans. This protocol can also be applied to any other drug molecule with diminished hydrophilic character.

Population Pharmacokinetics of Candesartan in Patients with Chronic Heart Failure.

Heart failure (HF) causes pathological changes in multiple organs, thus affecting the pharmacokinetics (PK) of drugs. The aim of this study was to investigate the PK of candesartan in patients with HF while examining significant covariates and their related impact on estimated clearance using a population PK (Pop-PK) modeling approach. Data from a prospective, multicenter study were used. Modeling and simulations were conducted using Nonlinear Mixed-Effects Modeling (NONMEM) and R software. A total of 281 white patients were included to develop the Pop-PK model. The final model developed for apparent oral clearance (CL/F) included weight, estimated glomerular filtration rate (eGFR), and diabetes, which partly explained its interindividual variability. The mean CL/F value estimated was 7.6 L/h (1.7-22.6 L/h). Simulations revealed that an important decrease in CL/F (> 25%) is obtained with the combination of the factors retained in the final model. Considering these factors, a more individualized approach of candesartan dosing should be investigated in patients with HF.

Study protocol for a multicentre, prospective cohort study of the association of angiotensin II type 1 receptor blockers on outcomes of coronavirus infection.

INTRODUCTION: The COVID-19 epidemic grows and there are clinical trials of antivirals. There is an opportunity to complement these trials with investigation of angiotensin II type 1 receptor blockers (ARBs) because an ARB (losartan) was effective in murine influenza pneumonia. METHODS AND ANALYSIS: Our innovative design includes: ARBs; alignment with the WHO Ordinal Scale (primary endpoint) to align with other COVID-19 trials; joint longitudinal analysis; and predictive biomarkers (angiotensins I, 1-7, II and ACE1 and ACE2). Our hypothesis is: ARBs decrease the need for hospitalisation, severity (need for ventilation, vasopressors, extracorporeal membrane oxygenation or renal replacement therapy) or mortality of hospitalised COVID-19 infected adults. Our two-pronged multicentre pragmatic observational cohort study examines safety and effectiveness of ARBs in (1) hospitalised adult patients with COVID-19 and (2) out-patients already on or not on ARBs. The primary outcome will be evaluated by ordinal logistic regression and main secondary outcomes by both joint longitudinal modelling analyses. We will compare rates of hospitalisation of ARB-exposed versus not ARB-exposed patients. We will also determine whether continuing ARBs or not decreases the primary outcome. Based on published COVID-19 cohorts, assuming 15% of patients are ARB-exposed, a total sample size of 497 patients can detect a proportional OR of 0.5 (alpha=0.05, 80% power) comparing WHO scale of ARB-exposed versus non-ARB-exposed patients. ETHICS AND DISSEMINATION: This study has core institution approval (UBC Providence Healthcare Research Ethics Board) and site institution approvals (Health Research Ethics Board, University of Alberta; Comite d'etique de la recerche, CHU Sainte Justine (for McGill University and University of Sherbrook); Conjoint Health Research Ethics Board, University of Calgary; Queen's University Health Sciences & Affiliated Hospitals Research Ethics Board; Research Ethics Board, Sunnybrook Health Sciences Centre; Veritas Independent Research Board (for Humber River Hospital); Mount Sinai Hospital Research Ethics Board; Unity Health Toronto Research Ethics Board, St. Michael's Hospital). Results will be disseminated by peer-review publication and social media releases. TRIAL REGISTRATION NUMBER: NCT04510623.

ABCB1 c.2677G>T/c.3435C>T diplotype increases the early-phase oral absorption of losartan.

Losartan has been shown to be a substrate of the drug-efflux transporter MDR1, encoded by the ABCB1 gene. ABCB1 c.2677G>T and c.3435C>T variants are known to be associated with reduced expression and function of P-glycoprotein (P-gp). We investigated the effects of ABCB1 diplotype on the pharmacokinetics of losartan. Thirty-eight healthy Korean volunteers with different ABCB1 diplotypes [c.2677G> T and c.3435C>T; carriers of GG/CC (n = 13), GT/CT (n = 12) and TT/TT (n = 13) diplotype] were recruited and administered a single 50 mg oral dose of losartan potassium. Losartan and its active metabolite E-3174 samples in plasma and urine were collected up to 10 and 8 h after drug administration, respectively, and the concentrations of both samples were determined by HPLC method. Significant differences were observed in Cmax of losartan and losartan plus E-3174 (Lo + E) among the three diplotype groups (both P < 0.01). However, the power of the performed test is less than the desired power (0.800). The tmax of losartan and E-3174 in three diplotype groups were also significantly different (both P < 0.01). The AUC values of Lo + E were significantly different among the three diplotype groups until 6 h after losartan administration (P < 0.01). On the contrary, AUC at the periods of 8-10 h and 10 h-infinity of Lo + E were significantly lower in the TT/TT group than in the GG/CC group. Urinary excretion of losartan until 4 h after losartan administration in the TT/TT group was higher than that of the GG/CC group. These results suggest that c.2677G>T/c.3435C>T diplotypes of ABCB1 may significantly increase the early-phase absorption of losartan, but not the total absorption.

Pharmacokinetics and Bioequivalence of Two Formulations of Valsartan 80 mg Capsules: A Randomized, Single Dose, 4-Period Crossover Study in Healthy Chinese Volunteers Under Fasting and Fed Conditions.

PURPOSE: To compare the bioequivalence of two formulations of valsartan (80 mg capsules) under fasting and fed conditions in healthy Chinese volunteers using a full-replicate study design. METHODS: A total of 78 Subjects were randomly assigned to fasting cohort (n = 48) or fed cohort (n = 30). Each cohort includes 4 single-dose observation periods and 3-day washout periods. Blood samples were collected at designed time point. Plasma concentration of valsartan was analyzed by a validated LC-MS/MS method. Noncompartmental analysis method was employed to determine the pharmacokinetic parameters. Based on the within-subject standard deviation (SWR) of the reference formulation, either reference-scaled average bioequivalence (RSABE) or average bioequivalence (ABE) method was used to evaluate the bioequivalence of the two formulations. RESULTS: Under fasting conditions, the RSABE method was used to evaluate the bioequivalence of Cmax (SWR>0.294), while ABE method was used to evaluate the bioequivalence of AUC0-t and AUC0-∞. The geometric mean ratio (GMR) of the test/reference for Cmax was 99.52%, and the 95% upper confidence bound was <0. For AUC0-t and AUC0-∞ comparisons, GMRs were 102.07% and 101.92%, and the 90% CIs of the test/reference were 96.28%-108.21%, 96.28%-107.88%, respectively. Under fed conditions, the SWR value of Cmax, AUC0-t and AUC0-∞ all exceeded the cutoff value of 0.294 and therefore, the RSABE method was used. The GMRs for Cmax, AUC0-t and AUC0-∞ were 98.78%, 103.33% and 103.08%, respectively, while the 95% upper confidence bound values were all <0. These results all met the bioequivalence criteria for highly variable drugs. All adverse events were mild and transient. CONCLUSION: In this study, the generic formulation of valsartan 80 mg capsule was considered to be bioequivalent to the reference product under both fasting and fed conditions, and satisfied the requirements for marketing in China. NMPA REGISTRATION NO: CTR20181422.

UGT1A3 and Sex Are Major Determinants of Telmisartan Pharmacokinetics-A Comprehensive Pharmacogenomic Study.

To investigate how variability in multiple pharmacokinetic genes associates with telmisartan exposure, we determined telmisartan single-dose (40 mg) pharmacokinetics and sequenced 379 genes in 188 healthy volunteers. Intronic UGT1A variants showed the strongest associations with the area under the plasma concentration-time curve from zero hours to infinity (AUC0-∞ ) and peak plasma concentration (Cmax ) of telmisartan. These variants were strongly linked with the increased function UGT1A3*2 allele, suggesting that it is the causative allele underlying these associations. In addition, telmisartan plasma concentrations were lower in men than in women. The UGT1A3*2 was associated with a 64% and 63% reduced AUC0-∞ of telmisartan in UGT1A3*2 heterozygous and homozygous men, respectively (P = 1.21 × 10-16 and 5.21 × 10-8 ). In women, UGT1A3*2 heterozygosity and homozygosity were associated with 57% (P = 1.54 × 10-11 ) and 72% (P = 3.31 × 10-15 ) reduced AUC0-∞ , respectively. Furthermore, a candidate gene analysis suggested an association of UGT1A3*3 and the SLCO1B3 c.767G>C missense variant with telmisartan pharmacokinetics. A genotype score, which reflects the effects of sex and genetic variants on telmisartan AUC0-∞ , associated with the effect of telmisartan on diastolic blood pressure. These data indicate that sex and UGT1A3 are major determinants and suggest a role for OATP1B3 in telmisartan pharmacokinetics.

The anti-Alzheimer effect of telmisartan in a hyperglycemic ovariectomized rat model; role of central angiotensin and estrogen receptors.

The central renin angiotensin system (RAS) is implicated in Alzheimer's disease (AD). Here, induction of experimental AD simulation was performed by D-galactose (D-Gal) injection to ovariectomized (OVX) rats fed on high fat high fructose diet (HFFD). Telmisartan administration to OVX/HFFD/D-Gal rats lowered the expression of hippocampal angiotensin 1 and 2 receptors and glucose transporter 2 in addition to lowering of the peripheral and central glucose levels. Furthermore, it improved cognitive impairment and suppressed hippocampal amyloidogenic markers including amyloid-beta level, phosphorylated tau protein and beta site amyloid precursor protein cleaving enzyme 1 expression, while elevated levels of insulin degrading enzyme and recovered permeability of blood brain barrier (BBB). In addition, it inhibited hippocampal oxido-nitrosative stress as well as neuroinflammatory and apoptotic biomarkers. Telmisartan improved memory and cognitive impairment as shown in the behavioral Morris water maze, Y-maze, novel object recognition and open field tests in addition to amelioration of depressive like behavior as shown in forced swimming test. Histopathological examination of brain and immune expression of glial fibrillary acidic protein were also improved together with astrogliosis improvement. In conclusion, telmisartan improved memory and cognitive impairment, recovered amyloidogenesis-hyperglycemic axis, astrogliosis, integrity of BBB, memory deficit and oxidonitrosative stress induced in OVX/HFFD/D-Gal rats.

Blood Pressure-Lowering Profiles and Clinical Effects of Angiotensin Receptor Blockers Versus Calcium Channel Blockers.

Blood pressure-lowering drugs have different blood pressure-lowering profiles. We studied if differences in blood pressure mean and variability can explain the differences in risks of cardiovascular events and death among 15 245 high-risk hypertensive patients randomized to valsartan or amlodipine and followed for 4.2 years in the VALUE trial (Valsartan Antihypertensive Long-Term Use Evaluation). We selected patients with ≥3 visits and performed Cox regression analyses, defining mean blood pressure as a time-dependent covariate and visit-to-visit and within-visit blood pressure variability as the SD. Of 14 996 eligible patients, participants in the valsartan group had higher systolic mean blood pressure by 2.2 mm Hg, higher visit-to-visit systolic variability by 1.4 mm Hg, and higher within-visit systolic variability by 0.2 mm Hg (P values <0.0001). The higher risks of myocardial infarction and stroke in the valsartan group was attenuated after adjustment for mean and variability of systolic blood pressure, from HR 1.19 (95% CI, 1.02-1.39) to 1.11 (0.96-1.30) and from HR 1.13 (0.96-1.33) to 1.00 (0.85-1.18), respectively. The lower risk of congestive heart failure in the valsartan group was accentuated after adjustment, from HR 0.86 (0.74-1.00) to 0.76 (0.65-0.89). A smaller effect was seen on risk of death, from 1.01 (0.92-1.12) to 0.94 (0.85-1.04). In conclusion, the higher risks of myocardial infarction and stroke in patients randomized to valsartan versus amlodipine were related to the drugs' different blood pressure modulating profiles. The risk of congestive heart failure with valsartan was lower, independent of the less favorable blood pressure modulating profile.

Modelling gastric emptying: A pharmacokinetic model simultaneously describing distribution of losartan and its active metabolite EXP-3174.

Losartan presents multiple peaks in the concentration-time profile. This characteristic can be attributed to gastric emptying, which is known to significantly affect the disposition of highly soluble and permeable compounds. The aim of this study was to develop a population pharmacokinetic model for losartan and its active metabolite (EXP-3174) in order to describe the effect of gastric emptying on their disposition. Population pharmacokinetic analysis was performed using concentration-time data derived from a crossover bioequivalence study in 31 volunteers after a single oral dose of 100 mg losartan potassium in the fasted state. Delay differential equations (DDEs) were explored for the description of losartan absorption and EXP-3174 formation, since when solved they result in oscillatory behaviour. A two-compartment model preceded by a pre-absorption compartment (referring to small intestine) adequately described the observed concentration-time profiles of losartan. In the final model, a sinusoidal equation was used for the description of gastric emptying in view of its simplicity, leading to enhanced stability of the model and its capacity to describe periodicity. In case of EXP-3174, a one-compartment model, with a delayed first-order formation rate from losartan's central compartment, best described its disposition. Using the model developed, it was shown through simulations that changes in gastric emptying parameters lead to changes in the C-t profiles of both compounds. In particular, plasma oscillations can be enhanced or completely suppressed, simply by changing parameters affecting gastric emptying.

Co amorphous valsartan nifedipine system: Preparation, characterization, in vitro and in vivo evaluation.

Co amorphous systems are supersaturated drug delivery systems which offer a basic platform for delivery of multicomponent adducts (combination of more than one active pharmaceutical ingredient (API)) and/or as a fixed dose combination therapy, in addition to their potential to improve the apparent solubility, dissolution rate and ultimately bioavailability of poorly water soluble APIs. In the present work, a new drug-drug co amorphous system namely valsartan-nifedipine was prepared by quench cooling technique. Prepared co amorphous system was characterized for its solid state behavior with the help of Fourier Transform Infrared spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and Powder X Ray Diffractometry (PXRD). The optimized co amorphous system was stable for 1 month when exposed to accelerated stability condition (40 ±â€¯2 °C and 75 ±â€¯5% RH). The improved stability of amorphous nifedipine in co amorphous system was attributed to improved miscibility and intra and intermolecular non-covalent interactions mainly due to presence of hydrogen bonding between valsartan and nifedipine which was studied by FTIR analysis. Co amorphous systems were evaluated by mainly in vitro dissolution and in vivo benefit. In vitro dissolution study showed nearly 5.66 folds and 1.61 folds improvement which was translated to 3.63 and 2.19 times enhancement in vivo Cmax for nifedipine and valsartan respectively.

Effects of UGT1A1 Polymorphism, Gender and Triglyceride on the Pharmacokinetics of Telmisartan in Chinese Patients with Hypertension: A Population Pharmacokinetic Analysis.

BACKGROUND AND OBJECTIVE: Telmisartan is an angiotensin receptor blocker used for the treatment of hypertension. The effects of gender and uridine diphosphate-glycosytransferase 1A1 (UGT1A1) genetic polymorphisms (rs4124874, rs4148323, and rs6742078) on telmisartan plasma concentration and blood pressure in Chinese patients with hypertension have been reported previously. In this study, we aimed to develop a population pharmacokinetic (PopPK) model to quantify the effects of gender and UGT1A1 polymorphisms on the pharmacokinetics of telmisartan. METHODS: Population pharmacokinetic analyses were performed using data collected prospectively from 58 Chinese patients with mild to moderate essential hypertension (aged 45-72 years; 36 men, 22 women) receiving 80 mg/day telmisartan orally for 4 weeks. Blood samples were collected in heparinized tubes at 0, 0.5, 1, and 6 h on day 28 after telmisartan administration. The plasma concentrations and UGT1A1 genetic variants were determined by high-performance liquid chromatography-mass spectrometry and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, respectively. RESULTS: A two-compartment pharmacokinetic structural model with first-order elimination and absorption best described the pharmacokinetic characteristics of telmisartan. Gender and triglyceride influenced the apparent oral clearance (CL) of telmisartan. UGT1A1 (rs4124874) affected the bioavailability (F1) of telmisartan. Lower CL and bioavailability resulted in higher plasma concentrations being observed in female subjects with UGT1A1 CC or CA genotype and high triglyceride. CONCLUSION: A PopPK model of telmisartan was established to confirm that UGT1A1 genotype, gender and triglyceride can affect the pharmacokinetics of telmisartan in Chinese patients with hypertension. Our findings can provide relevant pharmacokinetic parameters for further study of telmisartan.

Development and validation of reverse phase HPLC method for determination of angiotensin receptor blocking agent irbesartan in plasma.

A sensitive, reproducible and modest analytical procedure was developed and validated for evaluation of irbesartan in human plasma. LLE (Liquid-Liquid extraction) of the drug was carried out with acetonitrile (1:1 v/v). Chromatographic separation of irbesartan was conducted by the help of 4.0mm × 25cm column having L1 packing from plasma and mobile phase utilizing HPLC. The mobile phase comprise of phosphate buffer and acetonitrile in a ratio of 67:33 v/v. The flow rate was set at 1ml/minute and the detector at a wavelength of 220 nm. The resolution of irbesartan was well performed from plasma components. This method was validated and demonstrated linearity with a concentration range of 0.1to 6µg/ml of irbesartan in plasma. Intra-day, inter-day accuracy was found 89.33% to 96.37% while intra-day, inter-day precision was found within the limit of 0.02 and 2.15 respectively. The mean recovery of irbesartan was 97.28%. The efficacy of extraction was proved by above-mentioned results. In plasma, the 0.05 and 0.1µg/ml dilutions were exhibited as the LOD and LOQ of irbesartan. Stability studies disclosed that irbesartan showed stability at -20°C storage.

Analysis of the Complicated Nonlinear Pharmacokinetics of Orally Administered Telmisartan in Rats Using a Stable Isotope-IV Method.

This study aimed to kinetically analyze the nonlinear absorption and systemic exposure of telmisartan (TEL) after oral administration to rats by using a stable isotope-IV method. Rats were orally administered different dose of TEL, followed by the intravenous injection of 0.005 mg/kg of deuterium-labeled TEL (TEL-d3). Assuming that TEL-d3 shows same pharmacokinetic properties with TEL, systemic clearance (CLtot), oral bioavailability (Foral), and intestinal and hepatic availability (Fa*Fg, Fh) of TEL were calculated in each individual rat. AUCpo of TEL increased disproportionately with dose and showed a sigmoid-type relation, indicating the involvement of multi-nonlinear processes in oral absorption of TEL. Fa*Fg of TEL increased with dose at the low-dose range while decreased at the high-dose range. In contrast, Fh increased and CLtot decreased significantly in the middle range (2 to 6 mg/kg). As main factors of nonlinearity, saturations of solubility, efflux transport in the intestine, and the hepatic uptake of TEL were indicated. In conclusion, this study demonstrated a high possibility of a stable isotope-IV method to characterize complicated pharmacokinetic properties of oral drugs in animals, which can help to consider the future risks in their clinical use.