Combination therapy with AT(1)-receptor blockers

Simultaneous Determination and Pharmacokinetic Study of Losartan, Losartan Carboxylic Acid, Ramipril, Ramiprilat, and Hydrochlorothiazide in Rat Plasma by a Liquid Chromatography/Tandem Mass Spectrometry Method

The monitoring of the plasmatic concentrations of cardiovascular drugs is crucial for understanding their pharmacokinetics and pharmacodynamics. A simple, sensitive, specific, and high-throughput liquid chromatography/tandem mass spectrometry (LC–MS/MS) method was developed and validated for the simultaneous estimation and pharmacokinetic study of losartan (LOS), losartan carboxylic acid (LCA), ramipril (RAM), ramiprilate (RPT), and hydrochlorothiazide (HCZ) in rat plasma using irbesartan (IBS) and metolazone (MET) as internal standards (ISs). After solid phase extraction (SPE), analytes and ISs were separated on an Agilent Poroshell 120, EC-C18 (50 mm × 4.6 mm, i.d., 2.7 μm) column with a mobile phase consisting of methanol/water (85:15, v/v) containing 5 mmol/L ammonium formate and 0.1% formic acid at a flow rate of 0.4 mL/min. The precursor → product ion transitions for the analytes and ISs were monitored on a triple quadrupole mass spectrometer, operating in the multiple reaction monitoring (MRM) mode and switching the electrospray ionization (ESI) mode during chromatography from positive (to detect LOS, LCA, RAM, RPT, and IBS) to negative (to detect HCZ and MET). The method was validated as per the FDA guidelines and it exhibited sufficient specificity, accuracy, and precision. The method was found to be linear in the range of 3–3000 ng/mL for LOS and LCA, 0.1–200 ng/mL for RAM and RPT, and 1–1500 ng/mL for HCZ. The described method was successfully applied to the preclinical pharmacokinetic study of analytes after oral administration of a mixture of LOS (10 mg/kg), RAM (1 mg/kg), and HCZ (2.5 mg/kg) in rats.

Enhanced proliferation and altered calcium handling in RGS2-deficient vascular smooth muscle cells

CONTEXT

Regulator of G-protein signaling-2 (RGS2) inhibits Gq-mediated regulation of Ca(2+) signalling in vascular smooth muscle cells (VSMC).

OBJECTIVE

RGS2 knockout (RGS2KO) mice are hypertensive and show arteriolar remodeling. VSMC proliferation modulates intracellular Ca(2+) concentration [Ca(2+)]i. RGS2 involvement in VSMC proliferation had not been examined.

METHODS

Thymidine incorporation and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) conversion assays measured cell proliferation. Fura-2 ratiometric imaging quantified [Ca(2+)]i before and after UTP and thapsigargin. [(3)H]-labeled inositol was used for phosphoinositide hydrolysis. Quantitative RT-PCR and confocal immunofluorescence of select Ca(2+) transporters was performed in primary aortic VSMC.

RESULTS AND DISCUSSION

Platelet-derived growth factor (PDGF) increased S-phase entry and proliferation in VSMC from RGS2KO mice to a greater extent than in VSMC from wild-type (WT) controls. Consistent with differential PDGF-induced changes in Ca(2+) homeostasis, RGS2KO VSMC showed lower resting [Ca(2+)]i but higher thapsigargin-induced [Ca(2+)]i as compared with WT. RGS2KO VSMC expressed lower mRNA levels of plasma membrane Ca(2+) ATPase-4 (PMCA4) and Na(+) Ca(2+) Exchanger (NCX), but higher levels of sarco-endoplasmic reticulum Ca(2+) ATPase-2 (SERCA2). Western blot and immunofluorescence revealed similar differences in PMCA4 and SERCA2 protein, while levels of NCX protein were not reduced in RGS2KO VSMC. Consistent with decreased Ca(2+) efflux activity, (45)Ca-extrusion rates were lower in RGS2KO VSMC. These differences were reversed by the PMCA inhibitor La(3+), but not by replacing extracellular Na(+) with choline, implicating differences in the activity of PMCA and not NCX.

CONCLUSION

RGS2-deficient VSMC exhibit higher rates of proliferation and coordinate plasticity of Ca(2+)-handling mechanisms in response to PDGF stimulation.

Improving outcomes in hypertensive patients: focus on adherence and persistence with antihypertensive therapy

Although effective control of blood pressure (BP) reduces the risk of cardiovascular events in patients with hypertension, BP control rates among treated patients in actual clinical practice are less than optimal. Although the costs of medicines and medical care (which are difficult to estimate both in clinical trials and general clinical practice) are important, medication-taking behavior--adherence and persistence with antihypertensive regimens--influences BP control rates. Many factors affect adherence and persistence with medications, including efficacy and tolerability of drugs prescribed, such that rates vary greatly among antihypertensive classes. In general, medications with fewer adverse effects (in registration trials or large outcomes studies) are associated with increased adherence and lower discontinuation rates. More widespread use of such agents, particularly those available in generic formulations or in low-cost formularies, may lead to better long-term BP control and fewer cardiovascular events.

Efficacy and Safety of Valsartan/Hydrochlorothiazide Fixed-dose Combination Compared with Amlodipine Monotherapy as First-line Therapy for Mild to Moderate Hypertension

This double-blind, active- and randomized-controlled study compared the efficacy and safety of a fixed-dose combination of valsartan/hydrochlorothiazide 80 mg/12.5 mg once daily ( n = 32) with amlodipine monotherapy 5 mg once daily ( n = 33) for 8 weeks in patients with mild to moderate hypertension. Non-inferiority of valsartan/hydrochlorothiazide to amlodipine was demonstrated by comparable reductions in sitting systolic blood pressure (SBP), sitting diastolic blood pressure (DBP), and daytime, night-time and 24-h SBP and DBP on ambulatory blood pressure monitoring. Between-group comparisons of adverse events and changes in laboratory parameters did not reach statistical significance, except for uric acid which showed a significant increase in the valsartan/hydrochlorothiazide group compared with the amlodipine group, but was still below the laboratory's upper limit of normal. In conclusion, the use of the fixed-dose combination of valsartan/hydrochlorothiazide 80 mg/12.5 mg once daily as a starting regimen in patients with mild to moderate hypertension was shown to have non-inferior efficacy and comparable safety for daily practice compared with amlodipine 5 mg once daily monotherapy.

High performance liquid chromatography/negative ion electrospray tandem mass spectrometry method for the measurement of hydrochlorothiazide in human plasma: application to a comparative bioavailability study

A sensitive, selective and rapid liquid chromatography/tandem mass spectrometric (LC-MS/MS) method was developed and validated for the determination of hydrochlorothiazide (HCTZ) in human plasma. The plasma samples were prepared by solid phase extraction using Oasis HLB 30 mg 1CC cartridges. Chromatographic separation was accomplished on a Thermo Hypurity Advance (50 mm x 4.6mm i.d., 5 microm) column. The mobile phase consisted of HPLC Grade Acetonitrile: 2 mM Ammonium acetate (90 : 10 v / v) at a flow rate of 0.5 mL min(-1). Detection of hydrochlorothiazide and the internal standard (IS) zidovudine was achieved by ESI MS/MS in the negative ion mode. The total chromatographic runtime was 2.5 minutes. The linear range of the method was from 2.036-203.621 ng mL(-1). The mass transition ion pair has been followed as m/z 296.10/205.00 for HCTZ and 266.10/223.10 for Zidovudine. The mean overall recovery of HCTZ was 66.40% with a precision of 2.44%. The mean recovery of internal standard (Zidovudine) was 63.62% with a precision ranging from 2.06% to 5.40%. The method was successfully applied for the evaluation of pharmacokinetics of hydrochlorothiazide after single oral dose of 25 mg hydrochlorothiazide to healthy volunteers.

Dihydropyridine calcium channel antagonists in the management of hypertension

Dihydropyridine calcium channel antagonists have been maligned in recent years because of concerns regarding their cardiovascular and overall safety profile. Specifically, it was widely publicised in the mid-1990s that these agents might increase the risk of myocardial infarction, gastrointestinal bleeding and cancer. Data linking these agents with increased cardiovascular risk were based on nonrandomised studies and implicated short-acting, immediate-release agents. These results were inappropriately extrapolated to longer-acting compounds, extended-release products, and to the non-dihydropyridine class. Fortunately, recent studies have vindicated the class from safety allegations. These studies are reviewed herein. Compared with both diuretics and contemporary agents, amlodipine decreases cardiovascular events to a similar or greater extent without evidence for increased coronary heart disease, gastrointestinal bleeding or cancer. Despite these data, initial concerns have had lasting repercussions, as the use of dihydropyridine calcium channel antagonists appears to lag behind what emerging data would support. Dihydropyridine calcium channel antagonists have several noteworthy attributes that merit consideration in the management of hypertension. The blood pressure response to this class of drugs is less contingent on patient factors such as age and race compared with other antihypertensive agents (e.g. ACE inhibitors). Dihydropyridine calcium channel antagonists may exert effects that protect against stroke that are independent of their blood pressure-lowering mechanism. Unlike diuretics and beta-adrenoceptor anatagonists (beta-blockers), dihydropyridine calcium channel antagonists are lipid neutral and do not disturb glucose homeostasis. Dihydropyridine calcium channel antagonists demonstrate a highly desirable profile when administered as part of combination therapy. Combinations of dihydropyridine calcium channel antagonists and ACE inhibitors or angiotensin receptor antagonists display additive efficacy and an enviable adverse-effect profile. Collectively, the cardiovascular benefit, metabolic neutrality and homogeneous blood pressure response illuminated in recent studies, and reviewed here, represent a reaffirmation of the benefit of long-acting dihydropyridine calcium channel antagonists and should serve to help reinforce the critical importance of these agents in the therapeutic armamentarium against cardiovascular disease.

Lowering blood pressure for cardiovascular risk reduction

The association between blood pressure and cardiovascular risk is continuous, with no known lower threshold; epidemiologically, the lower the blood pressure, the better. In reality, the relationship must be J- or U-shaped, as a blood pressure of zero is associated with 100% mortality. However, the level of blood pressure control below which risk increases is well below that achieved in clinical practice, and reducing blood pressure is a cornerstone of strategies to reduce cardiovascular risk. Even relatively small reductions in blood pressure (systolic blood pressure 10-12 mmHg, diastolic blood pressure 5-6 mmHg) substantially reduce cardiovascular risk. Optimal cardiovascular protection is achievable through early and aggressive blood pressure control, but precisely which agents confer the greatest benefits for cardiovascular protection remains widely debated. Angiotensin II receptor blockers (ARBs) appear to be unique in providing additional protection beyond blood pressure control, whereas similar claims for other agents do not withstand close scrutiny. Nearly all patients with hypertension require several antihypertensive treatments to reach their target blood pressure, and it is important to choose treatments that are well tolerated and have complementary modes of action. For this reason, ARBs such as telmisartan emerge as logical choices for combination therapy, particularly when combined with a diuretic, as they fulfil all the essential requirements for combination therapy and are effective in a wide range of different types of patient. Regrettably, a rigorous approach to blood pressure control using multiple agents is still rare in general practice, partly because of a lack of understanding and partly because of 'professional non-compliance'. Prescribing habits must change, and soon, if we are to avoid an upsurge in cardiovascular complications.