Assessment of drug-drug interaction of dapagliflozin with LCZ696 based on an LC-MS/MS method.

The co-administration of dapagliflozin (DPF) and sacubitril/valsartan (LCZ696) has emerged as a promising therapeutic approach for managing heart failure. Given that DPF and LCZ696 are substrates for P-glycoprotein, there is a plausible potential for drug-drug interactions when administered concomitantly. To investigate the pharmacokinetic changes when these drugs are co-administered, we have established and validated a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method capable of simultaneously detecting DPF, LBQ657 (the active metabolite of sacubitril) and valsartan in rat plasma. This method has demonstrated selectivity, sensitivity, and accuracy. Drug-drug interactions were examined by the LC-MS/MS method. The mechanisms were investigated using everted intestinal sac models and Caco-2 cells. The results showed that DPF significantly increased the area under the curve (AUC(0-t)) (3,563.3 ± 651.7 vs. 7,146.5 ± 1,714.9 h µg/L) of LBQ657 (the active metabolite of sacubitril) and the AUC(0-t) (24,022.4 ± 6,774.3 vs. 55,728.3 ± 32,446.3 h µg/L) of valsartan after oral co-administration. Dapagliflozin significantly increased the amount of LBQ657 and valsartan in intestinal sacs by 1- and 1.25-fold at 2.25 h. Caco-2 cell uptake studies confirmed that P-glycoprotein is the transporter involved in this interaction. This finding enhances the understanding of drug-drug interactions in the treatment of heart failure and provides a guidence for clinical therapy.

Multivariate Assessment for Bioequivalence Based on the Correlation of Random Effect.

BACKGROUND AND OBJECTIVE: Bioequivalence tests are fundamental step in assessing the equivalence in bioavailability between a test and reference product. In practice, two separate linear mixed models (LMMs) with random subject effects, which have an area under the concentration-time curve (AUC) and the peak concentration (Cmax) as the responses, have become the gold standard for evaluating bioequivalence. Recently, Lee et al developed a multivariate hierarchical generalized linear model (HGLM) for several responses that modeled correlations among multivariate responses via correlated random effects. The objective of this study was to apply this multivariate analysis to the bioequivalence test in practice and to compare the performance of multivariate HGLM and separate LMMs. METHODS: Three pharmacokinetic datasets, fixed-dose combination (naproxen and esomeprazole), tramadol and fimasartan data were analyzed. We compared the 90% confidence interval (CI) for the geometric mean ratio (GMR) of a test product to a reference product using the multivariate HGLM and two conventional separate LMMs. RESULTS: We found that the 90% CIs for the GMRs of both AUC and Cmax from the multivariate HGLM were narrower than those from the separate LMMs: (0.843, 1.152) vs (0.825, 1.177) for Cmax of esomeprazole in fixed-dose combination data; (0.805, 0.931) vs (0.797, 0.941) for Cmax in tramadol data; (0.801, 1.501) vs (0.762, 1.578) for Cmax and (1.163, 1.332) vs (1.009, 1.341) for AUC in fimasartan data, consistent with the random subject effects from two separate LMMs being highly correlated in the three datasets (correlation coefficient r = 0.883; r = 0.966; r = 0.832). CONCLUSION: This multivariate HGLM had good performance in the bioequivalence test with multiple endpoints. This method would provide a more reasonable option to reduce the 90% CI by adding correlation parameters and thus an advantage especially in evaluating the bioequivalence of highly variable drugs with broad 90% CIs.

Quantitative bio-analysis of pitavastatin and candesartan in rat plasma by HPLC-UV: Assessment of pharmacokinetic drug-drug interaction.

A novel, precise, accurate and rapid HPLC-UV method was developed, optimised and fully validated for simultaneous estimation of pitavastatin (PIT) and candesartan (CAN) in rat plasma using telmisartan as an internal standard. Following liquid-liquid extraction of the analytes from plasma, chromatographic separation was accomplished on a Waters Reliant C18 column (4.6 × 250 mm, 5 µm) using ACN-5 mM Sodium acetate buffer (80:20, v/v; pH adjusted to 3.5 with acetic acid) as mobile phase at a flow rate of 0.8 mL/min and wavelength of 234 nm. The calibration curves were linear over the concentration ranges of 2-400 ng/mL and 3-400 ng/mL for pitavastatin and candesartan respectively. The method when validated as per US-FDA guidelines was found to be precise as well as accurate. Extraction recovery observed for both analytes was above 90% as well as reproducible and consistent. Stability studies showed the samples to be stable over a long period covering from sample collection to final analysis. The method was successfully applied to investigate pharmacokinetic interaction between PIT and CAN in wistar rats. The mean plasma concentration-time curves of PIT and CAN showed that single PIT as well as CAN show similar pharmacokinetic properties to those obtained when co-administrated with each other (P value >0.05). Hence, there is no evidence for a potential drug-drug interaction between PIT and CAN. This information provides evidence for clinical rational use of CAN and PIT in cardiovascular patients.

Reduced loop diuretic use in patients taking sacubitril/valsartan compared with enalapril: the PARADIGM-HF trial.

AIMS: To assess differences in diuretic dose requirements in patients treated with sacubitril/valsartan compared with enalapril in the Prospective comparison of ARNI with ACEI to Determine Impact on Global Mortality and morbidity in Heart Failure (PARADIGM-HF) trial. METHODS AND RESULTS: Overall, 8399 patients with New York Heart Association class II-IV heart failure and reduced LVEF were randomized to sacubitril/valsartan 200 mg bid or enalapril 10 mg twice daily. Loop diuretic doses were assessed at baseline, 6, 12, and 24 months, and furosemide dose equivalents were calculated via multiplication factors (2x for torsemide and 40x for bumetanide). Percentages of participants with reductions or increases in loop diuretic dose were determined. At baseline, 80.8% of participants were taking any diuretics (n = 6290 for loop diuretics, n = 496 for other diuretics); of those, recorded dosage data for loop diuretics were available on 5487 participants. Mean baseline furosemide equivalent doses were 48.2 mg for sacubitril/valsartan and 49.6 mg for enalapril (P = 0.25). Patients treated with sacubitril/valsartan were more likely to reduce diuretic dose and less likely to increase diuretic dose relative to those randomized to enalapril at 6, 12, 24 months post-randomization, with an overall decreased diuretic use of 2.0% (P = 0.02), 4.1% (P < 0.001), and 6.1% (P < 0.001) at 6, 12, and 24 months, respectively, with similar findings in an on-treatment analysis. CONCLUSION: Treatment with sacubitril/valsartan was associated with more loop diuretic dose reductions and fewer dose increases compared with enalapril, suggesting that treatment with sacubitril/valsartan may reduce the requirement for loop diuretics relative to enalapril in patients with heart failure with reduced ejection fraction.

The Sterilizing Effect of Intermittent Tedizolid for Pulmonary Tuberculosis.

Background: Linezolid exhibits remarkable sterilizing effect in tuberculosis; however, a large proportion of patients develop serious adverse events. The congener tedizolid could have a better side-effect profile, but its sterilizing effect potential is unknown. Methods: We performed a 42-day tedizolid exposure-effect and dose-fractionation study in the hollow fiber system model of tuberculosis for sterilizing effect, using human-like intrapulmonary pharmacokinetics. Bacterial burden was examined using time to positivity (TTP) and colony-forming units (CFUs). Exposure-effect was examined using the inhibitory sigmoid maximal kill model. The exposure mediating 80% of maximal kill (EC80) was defined as the target exposure, and the lowest dose to achieve EC80 was identified in 10000-patient Monte Carlo experiments. The dose was also examined for probability of attaining concentrations associated with mitochondrial enzyme inhibition. Results: At maximal effect, tedizolid monotherapy totally eliminated 7.1 log10 CFU/mL Mycobacterium tuberculosis over 42 days; however, TTP still demonstrated some growth. Once-weekly tedizolid regimens killed as effectively as daily regimens, with an EC80 free drug 0- to 24-hour area under the concentration-time curve-to-minimum inhibitory concentration (MIC) ratio of 200. An oral tedizolid of 200 mg/day achieved the EC80 in 92% of 10000 patients. The susceptibility breakpoint was an MIC of 0.5 mg/L. The 200 mg/day dose did not achieve concentrations associated with mitochondrial enzyme inhibition. Conclusions: Tedizolid exhibits dramatic sterilizing effect and should be examined for pulmonary tuberculosis. A tedizolid dose of 200 mg/day or 700 mg twice a week is recommended for testing in patients; the intermittent tedizolid dosing schedule could be much safer than daily linezolid.

Assessment of Drug-Drug Interaction Potential Between Atorvastatin and LCZ696, A Novel Angiotensin Receptor Neprilysin Inhibitor, in Healthy Chinese Male Subjects.

BACKGROUND AND OBJECTIVE: LCZ696 (sacubitril/valsartan), a novel angiotensin receptor neprilysin inhibitor has been recently approved for the treatment of patients with heart failure (HF) and reduced ejection fraction. As several HF patients are likely to use statins as co-medications, the potential for a pharmacokinetic drug-drug interaction between atorvastatin and LCZ696 was evaluated. METHODS: This was an open-label, three-period, single-sequence study in 28 healthy Chinese male subjects wherein LCZ696 200 mg was administered twice daily for 5 days in period 1. Following a washout period, atorvastatin 80 mg was administered once daily for 4 days (period 2) and subsequently co-administered with LCZ696 200 mg for 5 days (period 3). Serial plasma samples were collected to determine pharmacokinetic parameters of LCZ696 analytes (sacubitril, LBQ657, and valsartan) and atorvastatin and its metabolites. RESULTS: Atorvastatin co-administration had no effect on the pharmacokinetics of LBQ657, while the AUCτ,ss and C max,ss of sacubitril increased by 30 and 19 %, respectively, and the corresponding values for valsartan decreased by 19 and 9 %, respectively. Co-administration with LCZ696 increased C max,ss of atorvastatin, o-hydroxyatorvastatin, and p-hydroxyatorvastatin by 74, 68, and 108 %, respectively, and the AUCτ,ss of corresponding analytes increased by 34, 22, and 26 %, respectively. CONCLUSIONS: While atorvastatin had no significant impact on the pharmacokinetics of LCZ696 analytes upon co-administration, the C max of atorvastatin and its metabolites increased twofold, with a marginal increase in AUC (<1.3-fold). Multiple-dose administration of LCZ696 200 mg twice daily and atorvastatin 80 mg once daily either alone or in combination was generally safe and well tolerated in healthy subjects.

Pharmacokinetic drug-drug interaction assessment of LCZ696 (an angiotensin receptor neprilysin inhibitor) with omeprazole, metformin or levonorgestrel-ethinyl estradiol in healthy subjects.

LCZ696 is a novel angiotensin receptor neprilysin inhibitor in development for the treatment of cardiovascular diseases. Here, we assessed the potential for pharmacokinetic drug-drug interaction of LCZ696 (400 mg, single dose or once daily [q.d.]) when co-administered with omeprazole 40 mg q.d. (n = 28) or metformin 1000 mg q.d. (n = 27) or levonorgestrel-ethinyl estradiol 150/30 µg single dose (n = 24) in three separate open-label, single-sequence studies in healthy subjects. Pharmacokinetic parameters of LCZ696 analytes (sacubitril, LBQ657, and valsartan), metformin, and levonorgestrel-ethinyl estradiol were assessed. Omeprazole did not alter the AUCinf of sacubitril and pharmacokinetics of LBQ657; however, 7% decrease in the Cmax of sacubitril, and 11% and 13% decreases in AUCinf and Cmax of valsartan were observed. Co-administration of LCZ696 with metformin had no significant effect on the pharmacokinetics of LBQ657 and valsartan; however, AUCtau,ss and Cmax,ss of metformin were decreased by 23%. Co-administration of LCZ696 with levonorgestrel-ethinyl estradiol had no effect on the pharmacokinetics of ethinyl estradiol and LBQ657 or AUCinf of levonorgestrel. The Cmax of levonorgestrel decreased by 15%, and AUCtau,ss and Cmax,ss of valsartan decreased by 14% and 16%, respectively. Co-administration of LCZ696 with omeprazole, metformin, or levonorgestrel-ethinyl estradiol was not associated with any clinically relevant pharmacokinetic drug interactions.

Combined Angiotensin Receptor Antagonism and Neprilysin Inhibition.

Heart failure affects ≈5.7 million people in the United States alone. Angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, ß-blockers, and aldosterone antagonists have improved mortality in patients with heart failure and reduced ejection fraction, but mortality remains high. In July 2015, the US Food and Drug Administration approved the first of a new class of drugs for the treatment of heart failure: Valsartan/sacubitril (formerly known as LCZ696 and currently marketed by Novartis as Entresto) combines the angiotensin receptor blocker valsartan and the neprilysin inhibitor prodrug sacubitril in a 1:1 ratio in a sodium supramolecular complex. Sacubitril is converted by esterases to LBQ657, which inhibits neprilysin, the enzyme responsible for the degradation of the natriuretic peptides and many other vasoactive peptides. Thus, this combined angiotensin receptor antagonist and neprilysin inhibitor addresses 2 of the pathophysiological mechanisms of heart failure: activation of the renin-angiotensin-aldosterone system and decreased sensitivity to natriuretic peptides. In the Prospective Comparison of ARNI With ACEI to Determine Impact on Global Mortality and Morbidity in Heart Failure (PARADIGM-HF) trial, valsartan/sacubitril significantly reduced mortality and hospitalization for heart failure, as well as blood pressure, compared with enalapril in patients with heart failure, reduced ejection fraction, and an elevated circulating level of brain natriuretic peptide or N-terminal pro-brain natriuretic peptide. Ongoing clinical trials are evaluating the role of valsartan/sacubitril in the treatment of heart failure with preserved ejection fraction and hypertension. We review here the mechanisms of action of valsartan/sacubitril, the pharmacological properties of the drug, and its efficacy and safety in the treatment of heart failure and hypertension.

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.

Nonclinical and pharmacokinetic assessments to evaluate the potential of tedizolid and linezolid to affect mitochondrial function.

Prolonged treatment with the oxazolidinone linezolid is associated with myelosuppression, lactic acidosis, and neuropathies, toxicities likely caused by impairment of mitochondrial protein synthesis (MPS). To evaluate the potential of the novel oxazolidinone tedizolid to cause similar side effects, nonclinical and pharmacokinetic assessments were conducted. In isolated rat heart mitochondria, tedizolid inhibited MPS more potently than did linezolid (average [± standard error of the mean] 50% inhibitory concentration [IC50] for MPS of 0.31 ± 0.02 µM versus 6.4 ± 1.2 µM). However, a rigorous 9-month rat study comparing placebo and high-dose tedizolid (resulting in steady-state area under the plasma concentration-time curve values about 8-fold greater than those with the standard therapeutic dose in humans) showed no evidence of neuropathy. Additional studies explored why prolonged, high-dose tedizolid did not cause these mitochondriopathic side effects despite potent MPS inhibition by tedizolid. Murine macrophage (J774) cell fractionation studies found no evidence of a stable association of tedizolid with eukaryotic mitochondria. Monte Carlo simulations based on population pharmacokinetic models showed that over the course of a dosing interval using standard therapeutic doses, free plasma concentrations fell below the respective MPS IC50 in 84% of tedizolid-treated patients (for a median duration of 7.94 h) and 38% of linezolid-treated patients (for a median duration of 0 h). Therapeutic doses of tedizolid, but not linezolid, may therefore allow for mitochondrial recovery during antibacterial therapy. The overall results suggest that tedizolid has less potential to cause myelosuppression and neuropathy than that of linezolid during prolonged treatment courses. This, however, remains a hypothesis that must be confirmed in clinical studies.

Design, formulation and optimization of valsartan transdermal gel containing iso-eucalyptol as novel permeation enhancer: preclinical assessment of pharmacokinetics in Wistar albino rats.

OBJECTIVE: The aim of this study was to develop and optimize a transdermal gel formulation of valsartan using Box-Behnken design and to evaluate it for pharmacokinetic study. METHODS: The independent variables were Carbopol 940 (X1), PEG 400 (X2) and ethanol (X3) while valsartan flux (Y1), Tlag (Y2) and gel viscosity (Y3) were the dependent variables. Iso-eucalyptol was added in all gel formulations as permeation enhancer except for control gel. RESULTS: It was observed that the permeation rate of valsartan significantly increased in direct proportion to the ethanol concentration, but significantly decreased in direct proportion to polymer concentration. Lag time and viscosity decreased in reverse proportion to ethanol concentration. The optimized valsartan gel formulation (VGF-OPT) yielded flux of 143.27 ± 7.11 µg/cm(2)/h and 27.55 ± 2.51 µg/cm(2)/h across rat and human cadaver skin, respectively. In vivo pharmacokinetic study of VGF-OPT-transdermal therapeutic system containing iso-eucalyptol showed a significant increase in the bioavailability (2.52 times) compared with oral formulation of valsartan by virtue of better permeation through Wistar rat skin. CONCLUSION: It was concluded that the developed transdermal gel accentuates the flux of valsartan and could be used as an antihypertensive dosage form for effective transdermal delivery of valsartan.

Antihypertensive response to combination of olmesartan and amlodipine does not depend on method and time of drug administration.

Fixed combinations of antihypertensive drugs have the potentiality to improve blood pressure (BP) control. However, when pharmacokinetic parameters of the two drugs are different, both method and time of administration of the two drugs may modify the antihypertensive response. In an open-label, single-blind, randomized study we compared antihypertensive effect of four administration schemes of a combination therapy of olmesartan and amlodipine in the same group of hypertensive patients, using ambulatory blood pressure monitoring (ABPM). The olmesartan + amlodipine combination has demonstrated to provide a good control of BP, with systolic and diastolic BP constantly below 130 and 85 mmHg over the 24 h. The simultaneous or separate administration of the 2 drugs fully overlapped, suggesting that the fixed combination and the separate administration induce a similar and sustained BP control.

Inhibitors of HIV-1 attachment. Part 9: an assessment of oral prodrug approaches to improve the plasma exposure of a tetrazole-containing derivative.

7-(2H-Tetrazol-5-yl)-1H-indole 3 was found to be a potent inhibitor of HIV-1 attachment but the compound lacked oral bioavailability in rats. The cause of the low exposure was believed to be poor absorption attributed to the acidic nature of the tetrazole moiety and, in an effort to address this liability, three more lipohilic tetrazole analogs, N-acetoxymethyl 4, N-pivaloyloxymethyl 5, and N-methyl 6, were evaluated as potential oral prodrugs in rats. Prodrug 5 was ineffective in improving the plasma concentration of 3 in vivo but compound 4 provided a 15-fold enhancement of the plasma concentration of 3. Most interestingly, oral dosing of analog 6 afforded a substantial increase in the plasma concentration of the parent in rats when compared to dosing of parent. This represents a novel example of a methyl tetrazole that acts as a prodrug for a free NH tetrazole-containing compound.

The role of irbesartan in the treatment of patients with hypertension: a comprehensive and practical review.

Irbesartan is an orally active angiotensin II type 1 receptor antagonist (angiotensin receptor blocker [ARB]) whose pharmacological profile differs significantly from those of many other compounds of the same class. In particular, according to its pharmacokinetic and pharmacodynamic profile, irbesartan has a high bioavailability, a long duration of action and a small potential for pharmacological interactions due to the nature of the enzymatic pathway involved in its metabolic process. Morbidity data with irbesartan have been mainly accumulated in patients with renal impairment where the drug has demonstrated the most remarkable evidence of efficacy among the ARBs class, regardless of the stage of the renal disease (from early to late) and the length of the observational period. The efficacy of irbesartan has also been demonstrated in patients with left ventricular hypertrophy and congestive heart failure. The drug is indicated for the treatment of hypertension and renal impairment in patients with type 2 diabetes mellitus (T2D) and hypertension, and its tolerability and safety profile have been extensively investigated and reported to be similar to placebo. From the pharmacoeconomic point of view, treating patients with T2D, hypertension and overt nephropathy using irbesartan was both a cost- and life-saving procedure compared with the use of amlodipine and standard antihypertensive treatment in an Italian setting. The role of irbesartan in the management of hypertension with or without T2D and renal impairment is clearly recognized by national and international guidelines and largely acknowledged by the medical community according to the efficacy of the drug in the prevention of cardiovascular risk in addition to and beyond kidney prevention.

Assessment of the drug-drug interactions between fimasartan and hydrochlorothiazide in healthy volunteers.

AIM: Fimasartan is a selective angiotensin II receptor blocker. Hydrochlorothiazide (HCTZ), which is used to treat hypertension and edematous conditions, is coadministered with many antihypertensive agents. METHODS: An open-label, randomized, multiple-dosing, 2-arm, 1-sequence, 2-period study was conducted to assess the effects of fimasartan (240 mg) on HCTZ (25 mg) or vice versa in 18 and 14 healthy male volunteers, respectively. During each drug administration period, drugs were given once daily for 7 days, with a 7-day washout period between the 2 administration periods. RESULTS: The respective geometric mean ratios of fimasartan for AUC τ,ss and C max,ss with HCTZ were 1.30 [90% confidence interval (CI), 0.84-2.01] and 1.17 (90% CI, 0.93-1.47) compared with fimasartan alone. The respective geometric mean ratios of HCTZ for AUC τ,ss and C max,ss with fimasartan were 0.94 (90% CI, 0.84-1.04) and 0.88 (90% CI, 0.80-0.97) compared with HCTZ alone. Plasma renin activity indicated no significant differences between fimasartan monotherapy and coadministered treatment. CONCLUSIONS: Fimasartan administered alone or in combination with HCTZ was well tolerated at the described dosages. Coadministration of fimasartan increased the urinary excretion of HCTZ and urine volume, but these observations are unlikely to have any clinical relevance.

Challenges of therapeutic substitution of drugs for economic reasons: focus on CVD prevention.

BACKGROUND: Healthcare systems throughout the world are under increasing pressure to control and minimise costs. The substitution of initially-prescribed drugs with cheaper equivalents is an obvious option which presents a rapid and visible means to reduce these costs. Whether the substitution improves patient and/or population outcomes must be appraised and this paper highlights the conditions under which therapeutic substitution may require additional thought and consideration. SCOPE: In this paper, some of the medical evidence and the regulatory environment for and against the three types of therapeutic substitution - generic, within-class and between-class - are discussed. This article is not an exhaustive review of the literature, but captures some of the key clinical, pharmacological, economic, policy and ethical issues regarding generic and therapeutic substitution. Search criteria of the most commonly used terms, i.e. therapeutic substitution, switching, interchange, and bioequivalence, were applied to Embase, PubMed and Google Scholar to identify relevant publications. FINDINGS: Although population studies support therapeutic substitution in principle, there is evidence that substitution may not always result in therapeutic equivalence in individual patients, with the consequent potential for greater risks of decreased efficacy and/or increased safety concerns. Factors such as patient choice and therapeutic equivalence also play an important role in the effectiveness of the treatment and overall management of the patient. The pan-European regulatory environment provides another contradiction, encouraging widespread cost containment through reduction in drug acquisition costs, while simultaneously promoting an increased role for patients in defining and managing their own treatment. CONCLUSIONS: There is a strong rationale for careful management in some patients with cardiovascular disease. Treatment decisions should be transparent and based on strong clinical evidence. If not, drug substitution on economic grounds alone cannot be considered to be in the individual patient's interest and is therefore unethical.

Differences in pharmacology and their translation into differences in clinical efficacy--a comparison of the renin angiotensin blocking agents irbesartan and losartan.

IMPORTANCE OF THE FIELD: Guidelines recommend five antihypertensive drug classes, but which particular drug to choose is up to the treating physician. We aimed at an in-depth comparison of two frequently used angiotensin receptor blockers to provide evidence for this decision. AREAS COVERED IN THIS REVIEW: Pharmacology of irbesartan and losartan, their blood-pressure-lowering efficacy, their tolerability/safety, end-organ protective effects and economic evaluation. WHAT THE READER WILL GAIN: Both drugs differ in their oral bioavailability, potential for food interactions, degree of metabolism, dosing interval, time to peak, volume of distribution and terminal half-life. Irbesartan provides a greater and longer-lasting antihypertensive effect and was determined to be cost effective over losartan in Denmark and Sweden. Irbesartan was more effective in preventing deterioration of kidney function in patients with diabetic nephropathy, being cost effective from a German perspective. There is only one end point trial for either drug in patients with left ventricular hypertrophy, heart failure and atrial fibrillation, but no direct comparison. TAKE HOME MESSAGE: There is an incremental clinical benefit of irbesartan over losartan in the treatment of hypertension and diabetic nephropathy which can be substantiated by corresponding preclinical study evidence. This has translated into an economic benefit in a number of country-specific evaluations.

HPLC determination of irbesartan in human plasma: its application to pharmacokinetic studies.

A simple and rapid HPLC method using fluorescence detection was developed for determination of irbesartan in human plasma. Sample preparation was accomplished through a simple deproteinization procedure with 0.4 mL of acetonitrile containing 800 ng/mL of losartan (internal standard), and to a 0.1 mL plasma sample. Chromatographic separation was performed on a Zorbax Xclipse XDB C18 column (150 x 4.6 mm, i.d., 5 microm) at 40 degrees C. An isocratic mobile phase, acetonitrile:0.1% formic acid (37:63, v/v), was run at a flow-rate of 1.0 mL/min, and the column eluent was monitored using a fluorescence detector set at excitation and emission wavelengths of 250 and 370 nm, respectively. The retention times of irbesartan and losartan were 4.4 and 5.9 min, respectively. This assay was linear over a concentration range of 10-5000 ng/mL with a lower limit of quantification of 10 ng/mL. The coefficient of variation for this assay precision was less than 8.48%, and the accuracy exceeded 94.4%. The mean relative recoveries of irbesartan and losartan were 98.4 and 99.1%, respectively. This method was successfully applied for pharmacokinetic study after oral administration of irbesartan (300 mg) to 23 Korean healthy male volunteers.

Development and validation of a highly sensitive and robust LC-ESI-MS/MS method for simultaneous quantitation of simvastatin acid, amlodipine and valsartan in human plasma: application to a clinical pharmacokinetic study.

A high-throughput, simple, highly sensitive and specific LC-MS/MS method has been developed for simultaneous estimation of simvastatin acid (SA), amlodipine (AD) and valsartan (VS) with 500 microL of human plasma using deuterated simvastatin acid as an internal standard (IS). The API-4000 LC-MS/MS was operated under the multiple reaction-monitoring mode (MRM) using electrospray ionization. The assay procedure involved precipitation of SA, AD, VS and IS from plasma with acetonitrile. The total run time was 2.8 min and the elution of SA, AD, VS and IS occurred at 1.81, 1.12, 1.14 and 1.81 min, respectively; this was achieved with a mobile phase consisting of 0.02 M ammonium formate (pH 4.5):acetonitrile (20:80, v/v) at a flow rate of 0.50 mL/min on an X-Terra C18 column. A linear response function was established for the range of concentrations 0.5-50 ng/mL (r > 0.994) for VS and 0.2-50 ng/mL (r > 0.996) for SA and AD. The method validation parameters for all three analytes met the acceptance as per FDA guidelines. This novel method has been applied to human pharmacokinetic study.