Effect of conivaptan, a combined vasopressin V(1a) and V(2) receptor antagonist, on vasopressin-induced cardiac and haemodynamic changes in anaesthetised dogs

Effect of Low-Dose Vasopressin Infusion on Vital Organ Blood Flow in the Conscious Normal and Septic Sheep

The effect of low-dose vasopressin (AVP) on vital regional circulations may be clinically relevant but has not been fully described. We sought to determine the effect of low-dose AVP on systemic haemodynamics, coronary, mesenteric and renal circulations in the conscious normal and septic mammal.

We studied seven Merino sheep using a prospective randomized cross-over double-blind placebo-controlled animal design. We inserted flow probes around aorta, coronary, mesenteric and renal arteries and, three weeks later, we infused low-dose AVP (0.02 IU/min) or placebo in the normal and septic state induced by intravenous E.coli. In normal sheep, AVP (0.02 IU/min) induced a 17% decrease in mesenteric blood flow (393.0±134.9 vs 472.1± 163.8 ml/min, P<0.05) and a 14% decrease in mesenteric conductance (P<0.05). In septic sheep, AVP decreased heart rate and cardiac output by 28% and 22%, respectively (P<0.05). It also decreased mesenteric blood flow and mesenteric conductance by 23% (flow: 468.5±159.7 vs 611.3±136.3 ml/min, P<0.05; conductance: 6.3±2.7 vs 8.2±2.7 ml/min/mmHg; P<0.05). Renal blood flow was unchanged but urine output and creatinine clearance increased (P<0.05). We conclude that low-dose AVP infusion has similar effects in the normal and septic mammalian circulation: bradycardia, decreased cardiac output, decreased mesenteric blood flow and conductance and increased urine output and creatinine clearance. This information is important to clinicians considering its administration in humans.

Assessment of the Anti-anginal Effect of Tetramethylpyrazine Using Vasopressin-Induced Angina Model Rats

Intravenous tetramethylpyrazine has been widely used in China as a complementary and/or alternative medicine to treat patients with ischemic heart disease. We assessed the anti-anginal effect of tetramethylpyrazine (10 mg/kg, intravenously (i.v.), n=6) in comparison with that of its vehicle, saline (1 mL/kg, i.v., n=6), using vasopressin-induced angina model rats. First, Donryu rats were anesthetized with pentobarbital sodium (60 mg/kg, intraperitoneally (i.p.)), and the surface lead I electrocardiogram was continuously monitored. Administration of vasopressin (0.5 IU/kg, i.v.) to the rats depressed the S-wave level of the electrocardiogram, indicating the onset of subendocardial ischemia. However, pretreatment with tetramethylpyrazine suppressed the vasopressin-induced depression of the S-wave level, which was not observed following pretreatment with its vehicle alone (saline), suggesting that tetramethylpyrazine ameliorated the vasopressin-induced subendocardial ischemia in vivo. These results may provide experimental evidence for the empirically known clinical efficacy of tetramethylpyrazine against ischemic heart disease, and could provide clues to better understanding its in vivo mechanism of action.

Danhong injection attenuates cardiac injury induced by ischemic and reperfused neuronal cells through regulating arginine vasopressin expression and secretion

Ischemic stroke is associated with cardiac myocyte vulnerability through some unknown mechanisms. Arginine vasopressin (AVP) may exert considerable function in the relationship of brain damage and heart failure. Danhong injection (DHI) can protect both stroke and heart failure patients with good efficacy in clinics. The aim of this study is to investigate the mechanism of DHI in heart and brain co-protection effects to determine whether AVP plays key role in this course. In the present study, we found that both the supernatant from oxygen-glucose deprivation (OGD) and reperfused primary rat neuronal cells (PRNCs) and AVP treatment caused significant reduction in cell viability and mitochondrial activity in primary rat cardiac myocytes (RCMs). Besides, DHI had the same protective effects with conivaptan, a dual vasopressin V1A and V2 receptor antagonist, in reducing the RCM damage induced by overdose AVP. DHI significantly decreased the injury of both PRNCs and RCMs. Meanwhile, the AVP level was elevated dramatically in OGD and reperfusion PRNCs, and DHI was able to decrease the AVP expression in the injured PRNCs. Therefore, our present results suggested that OGD and reperfusion PRNCs might induce myocyte injury by elevating the AVP expression in PRNCs. The ability of DHI to reinstate AVP level may be one of the mechanisms of its brain and heart co-protection effects.

Arginine vasopressin as a target in the treatment of acute heart failure

Congestive heart failure (CHF) is one of the most common reasons for hospitalization in the United States. Despite multiple different beneficial medications for the treatment of chronic CHF, there are no therapies with a demonstrated mortality benefit in the treatment of acute decompensated heart failure. In fact, studies of inotropes used in this setting have demonstrated more harm than good. Arginine vasopressin has been shown to be up regulated in CHF. When bound to the V1a and/or V2 receptors, vasopressin causes vasoconstriction, left ventricular remodeling and free water reabsorption. Recently, two drugs have been approved for use that antagonize these receptors. Studies thus far have indicated that these medications, while effective at aquaresis (free water removal), are safe and not associated with increased morbidity such as renal failure and arrhythmias. Both conivaptan and tolvaptan have been approved for the treatment of euvolemic and hypervolemic hyponatremia. We review the results of these studies in patients with heart failure.

β-adrenergic receptor-mediated cardiac contractility is inhibited via vasopressin type 1A-receptor-dependent signaling

BACKGROUND

Enhanced arginine vasopressin levels are associated with increased mortality during end-stage human heart failure, and cardiac arginine vasopressin type 1A receptor (V1AR) expression becomes increased. Additionally, mice with cardiac-restricted V1AR overexpression develop cardiomyopathy and decreased β-adrenergic receptor (βAR) responsiveness. This led us to hypothesize that V1AR signaling regulates βAR responsiveness and in doing so contributes to development of heart failure.

METHODS AND RESULTS

Transaortic constriction resulted in decreased cardiac function and βAR density and increased cardiac V1AR expression, effects reversed by a V1AR-selective antagonist. Molecularly, V1AR stimulation led to decreased βAR ligand affinity, as well as βAR-induced Ca(2+) mobilization and cAMP generation in isolated adult cardiomyocytes, effects recapitulated via ex vivo Langendorff analysis. V1AR-mediated regulation of βAR responsiveness was demonstrated to occur in a previously unrecognized Gq protein-independent/G protein receptor kinase-dependent manner.

CONCLUSIONS

This newly discovered relationship between cardiac V1AR and βAR may be informative for the treatment of patients with acute decompensated heart failure and elevated arginine vasopressin.

Arginine vasopressin receptor antagonists (vaptans): pharmacological tools and potential therapeutic agents

Arginine vasopressin (AVP) attracted attention as a potentially important neurohormonal mediator of the heart failure (HF) syndrome and hyponatremic states in humans because AVP influences renal handling of free water, vasoconstriction and myocyte biology through activation of V₂ and V₁(a) receptors. Current research is exploring V₂- and dual V₁(a)/V₂ receptor antagonism for the treatment of hyponatremia, as well as for the congestion and edema associated with chronic HF, because vasopressin receptor antagonists might offer benefits in comparison with conventional loop diuretics. The purpose of this review is to update the current status of experimental and clinical studies with available vasopressin receptor antagonists (conivaptan and tolvaptan) and their potential role in the treatment of HF and hyponatremia of multiple causes.

Conivaptan and its role in the treatment of hyponatremia

Hyponatremia is the most common electrolyte abnormality in hospitalized patients and is associated with increased morbidity and mortality. The recognition of the central role that arginin vasopressin plays in the pathogenesis of hyponatremia and the discovery that its actions are mediated by stimulation of V(1A) and V(2) receptors have led to the development of a new class of drugs, the arginin vasopressin antagonists. Conivaptan is a nonselective V(1A) and V(2) receptors antagonist that was the first of this class to be approved by the FDA for the management of euvolemic and hypervolemic hyponatremia. Its short-term safety and efficacy for the correction of hyponatremia have been established by multiple double-blind, randomized, controlled studies. Blocking the effects of arginin vasopressin on V(2) receptors produces aquaresis--the electrolyte-sparing excretion of water--an ideal approach to correct hypervolemic hyponatremia. The nonselectivity of conivaptan offers a theoretical advantage for its use in heart failure that may merit further exploration.

Efficacy and safety of oral conivaptan, a vasopressin-receptor antagonist, evaluated in a randomized, controlled trial in patients with euvolemic or hypervolemic hyponatremia

BACKGROUND

In most cases of hyponatremia, arginine vasopressin secretion is inappropriately high. This placebo-controlled, randomized, double-blind multicenter study evaluated the efficacy and safety of oral conivaptan, a V1A/V2-receptor antagonist, in patients with euvolemic or hypervolemic hyponatremia.

METHODS

Eighty-three patients with serum [Na] less than 130 mEq/L were stratified by volume status and randomly assigned to placebo or conivaptan 40 or 80 mg/d for 5 days.

RESULTS

Conivaptan increased the baseline-adjusted area under the serum [Na]-time curve significantly more than placebo (P = 0.0001). Patients given either dose of conivaptan demonstrated a serum [Na] of 4 mEq/L or greater above baseline significantly faster than those given placebo (P < 0.001) and maintained that increase for a greater total time (P = 0.0001). The least squares mean change in serum [Na] from baseline to end of treatment was also significantly greater with conivaptan 40 and 80 mg/d (6.8 and 8.8 mEq/L, respectively) (P = 0.0001) than that with placebo (1.2 mEq/L). The percentage of patients who obtained an increase from baseline in serum [Na] of 6 mEq/L or greater or normal serum [Na] was significantly higher among patients given conivaptan 40 and 80 mg/d (67% and 88%, respectively) than among those given placebo (20%; P < 0.001). Conivaptan was well tolerated; the most frequent adverse events were urinary tract infection, anemia, pyrexia, cardiac failure, hypotension, and hypokalemia.

CONCLUSION

Oral conivaptan was effective in increasing serum [Na] in patients with euvolemic or hypervolemic hyponatremia and had a favorable safety profile.

Effects of novel vasopressin receptor antagonists on renal function and cardiac hypertrophy in rats with experimental congestive heart failure

Arginine vasopressin (AVP) plays an important role in renal hemodynamic alterations, water retention, and cardiac remodeling in congestive heart failure (CHF). The present study evaluated the acute and chronic effects of vasopressin V(1a) receptor subtype (V(1a)) and vasopressin V(2) receptor subtype (V(2)) antagonists on renal function and cardiac hypertrophy in rats with CHF. The effects of acute administration of SR 49059 [(2S)1-[(2R,3S)-5-chloro-3-(2-chlorophenyl)-1-(3,4-dimethoxybenzene-sulfonyl)-3-hydroxy-2,3-dihydro-1H-indole-2-carbonyl]-pyrrolidine-2-carboxamide)] (0.1 mg/kg) and SR 121463B (1-[4-(N-tert-butylcarbamoyl)-2-methoxybenzenesulfonyl]-5-ethoxy-3-spiro-[4-(2-morpholinoethoxy)cyclohexane]indol-2-one, fumarate; equatorial isomer) (0.3 mg/kg), V(1a) and V(2) antagonists, respectively, on renal function, and of chronic treatment (3.0 mg/kg/day for 7 or 28 days, via osmotic minipumps or p.o.), on water excretion and cardiac hypertrophy were studied in rats with aortocaval fistula and control rats. CHF induction increased plasma AVP (12.8 +/- 2.5 versus 32.2 +/- 8.3 pg/ml, p < 0.05). Intravenous bolus injection of SR 121463B to controls produced dramatic diuretic response (from 5.5 +/- 0.8 to 86.3 +/- 21.9 microl/min; p < 0.01). In contrast, administration of SR 49059 did not affect urine flow. Likewise, administration of SR 121463B, but not SR 49059, to rats with CHF significantly increased urinary flow rate from 20.8 +/- 6.4 to 91.6 +/- 26.5 microl/min (p < 0.01). The diuretic effects of SR 121463B were associated with a significant decline in urinary osmolality and insignificant change of Na+ excretion. In line with its acute effects, chronic administration of SR 121463B to CHF rats increased daily urinary volume 2 to 5-fold throughout the treatment period. Both SR 121463B and SR 49059 significantly reduced heart weight in CHF rats when administered for 4 weeks, but not 1 week. These results suggest that V(2) and V(1a) antagonists improve water balance and cardiac hypertrophy in CHF and might be beneficial for the treatment of water retention and cardiac remodeling in CHF.

Conivaptan: a dual vasopressin receptor v1a/v2 antagonist [corrected]

Several fluid retentive states such as heart failure, cirrhosis of the liver, and syndrome of inappropriate antidiuretic hormone secretion are associated with inappropriate elevation in plasma levels of arginine vasopressin (AVP), a neuropeptide that is secreted by the hypothalamus and plays a critical role in the regulation of serum osmolality and in circulatory homeostasis. The actions of AVP are mediated by three receptor subtypes V1a, V2, and V1b. The V1a receptor regulates vasodilation and cellular hypertrophy while the V2 receptor regulates free water excretion. The V1b receptor regulates adrenocorticotropin hormone release. Conivaptan is a nonpeptide dual V1a/V2 AVP receptor antagonist. It binds with high affinity, competitively, and reversibly to the V1a/V2 receptor subtypes; its antagonistic effect is concentration dependent. It inhibits CYP3A4 liver enzyme and elevates plasma levels of other drugs metabolized by this enzyme. It is approved only for short-term intravenous use. Infusion site reaction is the most common reason for discontinuation of the drug. In animals conivaptan increased urine volume and free water clearance. In heart failure models it improved hemodynamic parameters and free water excretion. Conivaptan has been shown to correct hyponatremia in euvolemic or hypervolemic patients. Its efficacy and safety for short-term use have led to the Food and Drug Administration (FDA) approval of its intravenous form for the correction of hyponatremia in euvolemic and hypervolemic states. Despite its ability to block the action of AVP on V1a receptors, no demonstrable benefit from this action was noted in patients with chronic compensated heart failure and it is not approved for this indication. Consideration should be given to further evaluation of its potential benefits in patients with acute decompensated heart failure.

Future pharmacologic agents for treatment of heart failure in children

The addition of new agents to the armamentarium of treatment options for heart failure in pediatric patients is exciting and challenging. Administration of these therapies to pediatric patients will require careful scrutiny of the data and skilled application. Developmental changes in drug metabolism, excretion, and distribution are concerning in pediatric patients, and inappropriate evaluation of these parameters can have disastrous results. Manipulation of the neurohormonal pathways in heart failure has been the target of most recently developed pharmacologic agents. Angiotensin receptor blockers (ARBs), aldosterone antagonists, beta-blockers, and natriuretic peptides are seeing increased use in pediatrics. In particular, calcium sensitizing agents represent a new frontier in the treatment of acute decompensated heart failure and may replace traditional inotropic therapies. Endothelin receptor antagonists have shown benefit in the treatment of pulmonary hypertension, but their use in heart failure is still debatable. Vasopressin antagonists, tumor necrosis factor inhibitors, and neutral endopeptidase inhibitors are also targeting aspects of the neurohormonal cascade that are currently not completely understood. The future of pharmacologic therapies will include pharmacogenomic studies on new and preexisting therapies for pediatric heart failure. The education and skill of the practitioner when applying these agents in pediatric heart failure is of utmost importance.

Current treatments and novel pharmacologic treatments for hyponatremia in congestive heart failure

Hyponatremia in congestive heart failure (CHF) is associated with increased morbidity and mortality, underlining the importance of adequate assessment and treatment of this electrolyte imbalance in patients with CHF. Current treatment options for hyponatremia in CHF include hypertonic saline solution, loop diuretics, fluid restriction, and other pharmacologic agents, such as demeclocycline, lithium carbonate, and urea. Hypertonic saline solution must be administered with extreme caution because excessively slow or rapid sodium correction can lead to severe neurologic adverse effects. Loop diuretics are useful for reducing the water retention caused by CHF. However, the potent diuresis induced by agents such as furosemide results in loss of sodium and other essential electrolytes, which may exacerbate hyponatremia. Fluid restriction is only moderately effective and often difficult to implement in the hospital setting. Agents such as demeclocycline and lithium have potentially serious renal and cardiovascular side effects. The arginine vasopressin (AVP) receptor antagonists are a promising new class of aquaretic agents that increase free-water excretion while maintaining levels of sodium and other essential electrolytes. Tolvaptan (OPC-41061), lixivaptan (VPA-985), and conivaptan (YM-087) are currently under development for the treatment of hyponatremia. Although tolvaptan and lixivaptan are selective for the vasopressin-2 (V(2)) receptor responsible for the antidiuretic actions of AVP, conivaptan demonstrates activity at both the V(2) receptor and the V(1a) receptor responsible for the vasoconstricting properties of AVP. This dual receptor activity may be particularly useful in patients with CHF. These patients may benefit from the increased cardiac output, reduced total peripheral resistance, and reduced mean arterial blood pressure that results from V(1a) receptor blockade as well as the reduced congestion, reduced cardiac preload, and increased sodium concentrations induced by V(2) receptor antagonism.

Intravenous administration of conivaptan hydrochloride improves cardiac hemodynamics in rats with myocardial infarction-induced congestive heart failure

We investigated the effects of intravenously administered conivaptan hydrochloride, a dual vasopressin V1A and V2 receptor antagonist, on cardiac function in rats with congestive heart failure following myocardial infarction, and compared results with those for the selective vasopressin V2 receptor antagonist SR121463A. Rats were subjected to left coronary artery occlusion to induce myocardial infarction, which in turn led to congestive heart failure. At 4 weeks after coronary occlusion, conivaptan (0.03, 0.1 and 0.3 mg/kg i.v.) dose-dependently increased urine volume and reduced urine osmolality in both myocardial infarction and sham-operated rats. SR121463A (0.3 mg/kg i.v.) also increased urine volume and decreased urine osmolality in myocardial infarction rats, to a degree comparable to that by conivaptan (0.3 mg/kg i.v.). At 6 weeks after surgery, myocardial infarction rats showed increases in right ventricular systolic pressure, right atrial pressure, left ventricular end-diastolic pressure and relative weights of the heart and the lungs, and a decrease in first derivative of left ventricular pressure (dP/dt(max))/left ventricular pressure, showing that congestive heart failure was well established. Conivaptan (0.3 mg/kg i.v.) significantly reduced right ventricular systolic pressure, left ventricular end-diastolic pressure, lung/body weight and right atrial pressure in myocardial infarction rats. Moreover, conivaptan (0.3 mg/kg i.v.) significantly increased dP/dt(max)/left ventricular pressure. SR121463A at a dose of 0.3 mg/kg i.v. significantly decreased left ventricular end-diastolic pressure and right atrial pressure, and tended to decrease right ventricular systolic pressure and relative lung weight in myocardial infarction rats. Although the aquaretic and preload-reducing effects of SR121463A were similar to those of conivaptan, SR121463A failed to improve dP/dt(max)/left ventricular pressure. These results suggest that dual vasopressin V1A and V2 receptor antagonists provide greater benefit than selective vasopressin V2 receptor antagonists in the treatment of congestive heart failure.

Vasopressin antagonists in heart failure

The recrudescence of interest in manipulation of the arginine vasopressin system and especially of V2 vasopressin receptor blockade in heart failure stems from the limited efficacy and possible detrimental effects of loop diuretics. The "braking phenomenon," hypertrophy of the collecting duct cells, and altered pharmacodynamics contribute to loop diuretic resistance in heart failure. Selective (tolvaptan) and nonselective (conivaptan) V2 vasopressin receptor antagonists now known as "vaptans" promote free-water excretion that is labeled aquaresis and correct hyponatremia in patients with severe heart failure. A large mortality study with tolvaptan in heart failure is presently ongoing.

Arginine Vasopressin Levels Are Elevated and Correlate With Functional Status in Infants and Children With Congestive Heart Failure

Background— Arginine vasopressin (AVP) is a vasoactive hormone that acts on the kidney to conserve solute-free water and produces a potent vasoconstrictive effect during hypovolemic states. AVP levels are elevated in adults with congestive heart failure (CHF), and early clinical trials using AVP antagonists are being conducted. The purpose of this study was to determine if AVP levels (1) are elevated in children with CHF attributable to left ventricular dysfunction or pulmonary overcirculation attributable to large left-to-right shunts and (2) can predict functional clinical status.

Methods and Results— AVP levels were measured in patients with dilated cardiomyopathy (DCM) and CHF and in patients with large left-to-right intracardiac shunts. Each patient with DCM (ejection fraction percent <40%) was classified as NYHA functional class I through IV when the AVP level was drawn. Serum sodium was measured, serum osmolality was calculated, and echocardiograms and chest radiographs were performed on all study patients. AVP levels were also measured in age-matched controls. Mean AVP level in children with DCM (n=27) was 10.3 pg/mL (±12.8) versus 3.7 pg/mL (±2.4) in controls (n=15) ( P <0.01). Mean AVP level in children with left-to-right shunts (n=14) was 13.9 pg/mL (±17.3) versus 3.5 pg/mL (±1.3) in controls (n=8) ( P <0.04). In patients with DCM, AVP levels correlated directly with NYHA functional class ( r 2 =0.73, P <0.001).

Conclusions— Arginine vasopressin levels are elevated in infants and children with CHF attributable to left ventricular dysfunction and in infants with large left-to-right intracardiac shunts. Furthermore, there is a direct relationship between AVP level and the severity of heart failure in patients with DCM.

Science Review: Vasopressin and the cardiovascular system part 2 - clinical physiology

Vasopressin is emerging as a rational therapy for vasodilatory shock states. In part 1 of the review we discussed the structure and function of the various vasopressin receptors. In part 2 we discuss vascular smooth muscle contraction pathways with an emphasis on the effects of vasopressin on ATP-sensitive K+ channels, nitric oxide pathways, and interaction with adrenergic agents. We explore the complex and contradictory studies of vasopressin on cardiac inotropy and coronary vascular tone. Finally, we summarize the clinical studies of vasopressin in shock states, which to date have been relatively small and have focused on physiologic outcomes. Because of potential adverse effects of vasopressin, clinical use of vasopressin in vasodilatory shock should await a randomized controlled trial of the effect of vasopressin's effect on outcomes such as organ failure and mortality.