Hemodynamic effects of an oral dopamine receptor agonist (fenoldopam) in patients with congestive heart failure

Fenoldopam for the prevention of contrast-induced nephropathy (CIN)-do we need more trials? A meta-analysis

We conducted a pooled analysis of clinical trials comparing intravenous Fenoldopam (FP) with Saline/Placebo/N-acetyl cysteine (NAC) for the prevention of contrast-induced nephropathy (CIN). Five studies were eligible. Quantitative analyses were done with Review Manager (RevMan version 5.2.). A total of 85 out of 353 patients in Fenoldopam group while 73 among 366 in the control group were affected due to CIN. The risk ratio for the development of CIN in the Fenoldopam group was 1.19 compared to the control group. This was not statistically significant. Fenoldopam is no better than Placebo/Saline or NAC in preventing CIN, but more studies are required.

Beneficial Impact of Fenoldopam in Critically Ill Patients With or at Risk for Acute Renal Failure: A Meta-Analysis of Randomized Clinical Trials

BACKGROUND

Acute kidney injury is common in critically ill patients. Fenoldopam mesylate is a potent dopamine A-1 receptor agonist that increases blood flow to the renal cortex and outer medulla. Because there is uncertainty about the benefits of fenoldopam in such a setting, we performed a systematic review of randomized controlled trials of intensive care unit patients or those undergoing major surgery.

METHODS

BioMedCentral, CENTRAL, PubMed, and conference proceedings were searched (updated October 2005). Investigators and external experts were contacted. Two unblinded reviewers selected randomized controlled trials that used fenoldopam in the prevention or treatment of acute kidney injury in postoperative or intensive care patients. Studies involving the prevention of contrast nephropathy or containing duplicate data were excluded from analysis. Two reviewers independently abstracted patient data, treatment characteristics, and outcomes.

RESULTS

A total of 1,290 patients from 16 randomized studies were included in the analysis. Pooled estimates showed that fenoldopam consistently and significantly reduced the risk for acute kidney injury (odds ratio [OR], 0.43; 95% confidence interval [CI], 0.32 to 0.59; P < 0.001), need for renal replacement therapy (OR, 0.54; 95% CI, 0.34 to 0.84; P = 0.007), and in-hospital death (OR, 0.64; 95% CI, 0.45 to 0.91; P = 0.01). These benefits were associated with shorter intensive care unit stay (weighted mean difference, -0.61 days; 95% CI, -0.99 to -0.23; P = 0.002). Sensitivity analyses, tests for small-study bias, and heterogeneity assessment further confirmed the main analysis.

CONCLUSION

This analysis suggests that fenoldopam reduces the need for renal replacement and mortality in patients with acute kidney injury. A large, multicenter, appropriately powered trial will need to be performed to confirm these results.

Fenoldopam for controlled hypotension during spinal fusion in children and adolescents

Fenoldopam is a dopamine1 agonist whose pharmacological effects include vasodilation of the vascular beds of the kidney, mesentery, skeletal muscle, and coronary systems, resulting in a decrease in systemic vascular resistance and mean arterial pressure. The current retrospective review outlines the use of fenoldopam for controlled hypotension during anterior or posterior spinal fusion in 10 children and adolescents, aged 8-14 years and weighing 22-61 kg. Fenoldopam was infused at a starting dose of 0.3-0.5 microg.kg-1. min-1 and increased incrementally to achieve a mean arterial pressure (MAP) of 50-65 mmHg. The desired MAP was achieved in 4-11 min (7+/-2.5 min). The fenoldopam infusion was administered for 135-225 min (160+/-25 min) in doses ranging from 0.2 to 2.5 microg. kg-1.min-1. The mean fenoldopam infusion rate for the 10 cases varied from 0.5 to 1.4 microg.kg-1.min-1 (1.0+/-0.3 microg.kg-1. min-1). No excessive hypotension or clinically significant adverse effects were noted. Statistically significant, but clinically insignificant, increases in heart rate and decreases in PaO2 were noted during the fenoldopam infusion. The baseline heart rate increased from 87+/-13 b.min-1 to a maximum of 114+/-16 b.min-1 (P < 0.0001) during the fenoldopam infusion. In the six patients undergoing posterior spinal fusion, the baseline PaO2 decreased from 232+/-7 mmHg to a low of 199+/-11 mmHg (P=0.0004) during the fenoldopam infusion. Fenoldopam can be used to provide controlled hypotension during spinal surgery in children and adolescents. Future studies, with direct comparison to other commonly used agents, are needed to better define its advantages and disadvantages as well as its effects on estimated blood loss.

Fenoldopam: a new dopamine agonist for the treatment of hypertensive urgencies and emergencies

Fenoldopam is a selective dopamine agonist that is being considered for the parenteral treatment of systemic hypertension. In both an oral and parenteral form, the drug causes peripheral vasodilation by stimulating dopamine-1 adrenergic receptors. Its pharmaco-dynamics are reviewed in this article, along with the clinical experiences in patients with hypertensive urgencies and emergencies. Intravenous fenoldopam may provide advantages over sodium nitroprusside because it can induce both a diuresis and natriuresis, is not light sensitive, and is not associated with cyanide toxicity. There is no evidence for rebound hypertension after discontinuation of fenoldopam influsion.

[Dopexamine: a new dopaminergic agonist]

Dopexamine hydrochloride is a new synthetic catecholamine for intravenous use in low cardiac output states with co-existing raised systemic or pulmonary vascular resistance. Dopamine has been commonly used since several years in these situations. The drawbacks of dopamine include a vasoconstrictive effect with high infusion rates, and a marked tendency for ventricular ectopy due to the potent beta-1 adrenergic stimulation. Dopexamine hydrochloride has interesting vasodilator properties, with marked intrinsic agonist activity at beta-2 adrenoreceptors and a lesser agonist activity at dopaminergic receptors (DA1 and DA2). Its mild inotropic activity arises primarily from baroreceptor reflex stimulation with a possible contribution from direct stimulation of myocardial beta 2-adrenoreceptors. Dopexamine hydrochloride is responsible for an inhibition of neuronal re-uptake of catecholamines (uptake-1), producing an indirect stimulation of cardiac beta 1-receptors. This catecholamine has no effect at alpha 1 and alpha 2-adrenoreceptors, and only very weak and clinically insignificant beta 1-adrenoreceptor agonist activity. Dopexamine hydrochloride improves cardiac performance by a marked vasodilation and a mild inotropic activity. The specific activity at dopaminergic receptors increases cerebral, myocardial, splanchnic and renal blood flows. These haemodynamic effects are associated with an increase in diuresis and natriuresis. These benefits are achieved without side effects such as an increased myocardial oxygen consumption, although induced tachycardia may be responsible for chest pain/anginae pain in patients with ischaemic heart disease. In clinical practice, dopexamine hydrochloride is easy to use; the short plasma half-life (6 minutes in healthy volunteers and 11 minutes in patients with low cardiac output) allows a rapid return to pretreatment status at discontinuation of the infusion. Preliminary studies have shown that dopexamine hydrochloride can produce beneficial effects in patients with acute heart failure or with compromised left ventricular function following cardiac surgery. The drug has also been assessed in patients with septic shock, most often in association with dopamine or norepinephrine. In these patients, dopexamine produces a dose-related increase in cardiac index, stroke volume, heart rate and a decrease in systemic vascular resistance. Its use in this indication must be cautious, particularly in patients with hypotension or decreased venous return. Comparative therapeutic trials are clearly required to establish the efficiency and tolerance of dopexamine hydrochloride in comparison with dopamine and dobutamine, before its place in therapy can fully be defined.

Inotropic therapy of the failing myocardium

The clinical syndrome of congestive heart failure remains a therapeutic dilemma and challenge for the physician in 1992. This is a disease process that appears to be increasing in frequency and continues to carry an unacceptably high mortality rate. For years it has been well recognized that the combination of digoxin, Lasix and vasodilator therapy improved symptoms in these patients and decreased hospitalization, but did not increase survival. It was not until 1986 that the combination of digoxin, Lasix, Isordil, and hydralazine was shown to increase survival. Further significant improvement in quality of life and survival has recently been established in three large clinical trials, and it is now safe to say that the standard of care for symptomatic congestive heart failure in 1992 is digoxin, furosemide, and an ACE inhibitor, with the survival trials favoring the ACE inhibitor enalapril. The IV inotropic drug dobutamine remains the mainstay of pharmacological therapy for the treatment of severely refractory heart failure. Unfortunately, the phosphodiesterase inhibitors--amrinone, milrinone, and enoximone--have demonstrated unacceptable clinical side effects and have been withdrawn from further clinical study. In spite of these promising developments, the mortality and morbidity of congestive heart failure remains unacceptably high, and continued investigation in the new fields of pharmacology and the pathophysiology of congestive heart failure still must be aggressively pursued.

Selective dopamine-1 receptor agonist augments regional myocardial blood flow: Comparison of fenoldopam and dopamine

A new class of vasodilators exhibiting selective dopamine-1 receptor agonist activity is being introduced into clinical practice. Inasmuch as various vasodilators either augment or decrease myocardial blood flow ("coronary steal") depending on their pharmacologic action, the goal of this study was to assess the effects of fenoldopam (selective dopamine-1 receptor agonist) and dopamine (nonselective dopamine-1 receptor agonist) on regional myocardial blood flow in the presence of coronary occlusion. Accordingly, in 16 dogs anesthetized with pentobarbital, the left anterior descending coronary artery was occluded. Cardiovascular and renal hemodynamic effects were measured before and after intravenous infusion of renal equipotent doses of either fenoldopam (n = 9, 0.1 micrograms/kg/min) or dopamine (n = 7, 1 micrograms/kg/min). Both fenoldopam and dopamine caused a significant and comparable increase in renal blood flow. Fenoldopam but not dopamine significantly decreased the calculated peripheral vascular resistance and subsequently increased cardiac output. Dopamine had no effect on regional myocardial blood flow. In contrast, fenoldopam augmented transmural myocardial blood flow in normal (from 114 +/- 10 to 188 +/- 27 ml/100 gm/min, p less than 0.02) and ischemic border myocardium (from 45 +/- 5 to 68 +/- 11 ml/100 gm/min, p less than 0.03 and p less than 0.02 vs dopamine). There was a significant increase in blood flow to both the endocardial and epicardial layers of normal and ischemic border myocardium. These changes were accompanied by a significant reduction in coronary vascular resistance in the normal myocardium.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiovascular pharmacology of adrenergic and dopaminergic receptors: therapeutic significance in congestive heart failure

This review discusses the localization of adrenergic- and dopaminergic-adrenoceptors within the cardiovascular system and describes the cardiovascular and renal changes produced following the activation of these receptors by appropriate agonists. Whereas the role of alpha- and beta-adrenergic agents in the treatment of heart failure is well recognized, recent studies with dopamine (DA)-receptor agonists indicate that they offer a novel approach in the therapy of congestive heart failure. DA-adrenoceptor agonists reduce afterload by causing vasodilation and promote sodium excretion via direct activation of DA1-adrenoceptors located on renal tubules. Fenoldopam is a selective DA1-adrenoceptor agonist found to be effective in heart failure. It reduces afterload by causing peripheral vasodilation and produces natriuresis and diuresis. Dopexamine is a DA1- and beta 2-adrenoceptor agonist, and its efficacy in heart failure is due to its ability to provide mild inotropic support and cause a reduction in afterload. Ibopamine is a prodrug that is converted into its active metabolite, epinine. This compound activates primarily DA1- and DA2-adrenoceptors. It is effective in heart failure, and the mechanism progresses via DA1- and DA2-adrenoceptor-mediated reduction in afterload. Agonists of DA2-adrenoceptors reduce afterload by decreasing the release of norepinephrine and by reducing the levels of renin-angiotensin-aldosterone system. Since both of these systems are active in heart failure, ibopamine offers a rational approach for therapy. The present review addresses the concept of pharmacologic intervention in adrenergic and dopaminergic influence in the cardiovascular and renal systems to produce changes that are desirable for the pharmacotherapy of congestive heart failure.

A single dose study of the effects of fenoldopam and enalapril in mild hypertension

To clarify the contribution made by the renin-angiotensin system activation to the short lived hypotensive response to fenoldopam, the haemodynamic effects of a combination of fenoldopam (100 mg) and enalapril (5 mg) were compared with fenoldopam alone, enalapril alone and placebo in a balanced, randomised, double blind, single dose study in eight hypertensive patients. Fenoldopam caused an acute fall in blood pressure which lasted approximately 3 h after dosing and was associated with a reflex tachycardia. Enalapril caused a more gradual fall in blood pressure (onset 2 h) without a reflex tachycardia. The combination of drugs produced greater reductions in blood pressure sustained for a longer period than fenoldopam alone and with a more rapid onset than enalapril alone. In combination the hypotensive effects of fenoldopam and enalapril were clearly additive and not synergistic. Activation of the renin-angiotensin system does not antagonise significantly the hypotensive effect of fenoldopam.

Medical management of chronic heart failure: inotropic, vasodilator, or inodilator drugs?

On the basis of pathophysiologic mechanisms, the medical therapy of today for chronic heart failure is reviewed. The advantages and disadvantages of the vasodilator drugs and the inotropic drugs are presented. Finally, the therapeutic value of the inodilator drugs, which combine the central myocardial effects of positive inotropic agents with those of peripheral vasodilators, is discussed. In particular, the orally available dopaminergic agents, such as ibopamine, which interact with beta-receptors in the heart (mediating a positive inotropic effect) as well as with dopaminergic receptors in the peripheral vessels (mediating a systemic vasodilator effect) and in the kidneys (potentiating the natriuretic effect of diuresis), seem to be an advancement in the modern medical therapy of chronic heart failure. Data are shown during long-term treatment with ibopamine, in which the sustained clinical benefit in heart failure was not diminished, despite a decrease of the adrenergic receptors in blood cells. Dopamine plasma concentration was permanently normalized during long-term treatment. The discrepancy between clinical improvement and the measured adrenergic downregulation may be due to the interference of the inodilator with neurohormonal systems at multiple sites and is probably independent of receptor activation. It is suggested that the biosynthesis of noradrenaline is improved by increasing intracellular dopamine transport.

Development of dopaminergic drugs for the chronic treatment of congestive heart failure

1. The search of orally active dopaminergic drugs for the chronic treatment of congestive heart failure has followed two different approaches. 2. On the one hand, a selective DA-1 receptor agonist, such as fenoldopam, has been investigated as an agent developed for the stimulation of vascular and tubular DA-1 receptors in the kidney. On the other hand, orally active prodrugs were synthetized with the aim of mimicking the full pattern of dopaminergic and adrenergic actions of intravenous dopamine. 3. Ibopamine, the diisobutyric ester of N-methyldopamine, has shown effects comparable to those of dopamine in various animal models and in clinical investigations. Furthermore, patients suffering from mild or severe congestive heart failure were shown to benefit from ibopamine treatment in a number of therapeutic trials. 4. Limited experience is currently available on other prodrugs, such as docarpamine and Sim 2055, i.e. the 4-0-phosphate ester of N-methyldopamine. The latter is an analogue of ibopamine designed for a preferential delivery of N-methyldopamine in the kidney. 5. Based upon some additional studies with levodopa, the results suggest that a combination of DA-1 and DA-2 agonistic activity is a desirable feature of a new drug, since it appears suitable to provide vasodilation while counteracting the neurohumoral abnormality of congestive heart failure.

Preservation of renal blood flow during hypotension induced with fenoldopam in dogs

The introduction of drugs that could induce hypotension with different pharmacological actions would be advantageous because side effects unique to a specific drug could be minimized by selecting appropriate therapy. Specific dopamine-1, (DA1) and dopamine-2 (DA2) receptor agonists are now under clinical investigation. Fenoldopam mesylate is a specific DA1 receptor agonist that lowers blood pressure by vasodilatation. The hypothesis that fenoldopam could be used to induce hypotension and preserve blood flow to the kidney was tested. Systemic aortic blood pressure and renal blood flow were measured continuously with a carotid arterial catheter and an electromagnetic flow probe respectively, in order to compare the cardiovascular and renal vascular effects of fenoldopam and sodium nitroprusside in ten dogs under halothane general anaesthesia. Mean arterial pressure was decreased 30 +/- 8 per cent from control with infusion of fenoldopam (3.4 +/- 2.0 micrograms.kg-1.min-1) and 34 +/- 4 per cent with infusion of sodium nitroprusside (5.9 micrograms.kg-1.min-1) (NS). Renal blood flow (RBF) increased during fenoldopam-induced hypotension 11 +/- 7 per cent and decreased 21 +/- 8 per cent during sodium nitroprusside-induced hypotension (P less than 0.01). Sodium nitroprusside is a non-selective arteriolar and venous vasodilator that can produce redistribution of blood flow away from the kidney during induced hypotension. Fenoldopam is a selective dopamine-1 (DA1) receptor agonist that causes vasodilatation to the kidney and other organs with DA1 receptors and preserves blood flow to the kidney during induced hypotension.

Renal and hemodynamic effects of intravenous fenoldopam versus nitroprusside in severe hypertension

The renal and hemodynamic effects of intravenously administered fenoldopam mesylate, a novel dopamine-1 receptor agonist, were compared with those of sodium nitroprusside in 28 patients (18 male; 26 black, two white; average age, 49 +/- 3 years) with an average blood pressure of 219/137 mm Hg, most of whom presented with acute target organ damage. Fenoldopam and nitroprusside lowered blood pressure safely to an average pressure of 176/105 mm Hg; highly significant dose-response relations were found for the 13 patients receiving fenoldopam and the 15 receiving nitroprusside. Volume and sodium, potassium, and creatinine concentrations were measured in freely voided urine specimens both before and during intravenous therapy. In the fenoldopam-treated patients, there were significant increases in urinary flow (92 +/- 21 to 168 +/- 37 ml/hr, p less than 0.003), sodium excretion (227 +/- 73 to 335 +/- 90 mu eq/min, p less than 0.001), and creatinine clearance (70 +/- 11 to 93 +/- 13 ml/hr, p less than 0.003). In the nitroprusside-treated group, however, all these parameters decreased, but not significantly. For direct comparison of the two agents, the increments in urinary flow rate (+76 +/- 20 vs. -16 +/- 15 ml/hr, fenoldopam vs. nitroprusside), sodium excretion (+109 +/- 28 vs. -39 +/- 28 mu eq/min), and creatinine clearance (+23 +/- 6 vs. -11 +/- 7 ml/min) were significantly greater (p less than 0.001 for each) in the fenoldopam-treated group. Significant differences were also obtained when these parameters were calculated as percentage increase over baseline. Fenoldopam and nitroprusside are effective therapies for severe, accelerated, or malignant hypertension, but fenoldopam had additional salutary renal effects in these patients.

Assessment of hemodynamic tolerance from a 24-hour intravenous infusion of fenoldopam mesylate in congestive heart failure

To determine the maintenance of pharmacodynamic effects of fenoldopam mesylate, a dopamine-1 agonist, the invasive hemodynamic profiles of 33 patients with New York Heart Association functional class III to IV congestive heart failure were examined. Fenoldopam mesylate was initiated at 0.1 micrograms/kg/min and titrated to a cardiac index greater than or equal to 25% above baseline. Upon achievement of optimal hemodynamics, maintenance infusion was begun (mean dose 0.6 micrograms/kg/min). Fenoldopam mesylate (baseline vs maximal effect) decreased systemic vascular resistance by 37% (p less than 0.001), left ventricular filling pressure by 16% (p less than 0.05) and mean arterial pressure by 11% (p less than 0.05), with an associated augmentation in cardiac index and stroke volume index by 27% (p less than 0.001). Attenuation of hemodynamic effect (maximal effect vs time) was noted in cardiac index (14% p less than 0.001), systemic vascular resistance (13% p less than 0.05) and stroke volume index (13% p less than 0.05). None of the parameters exhibited complete attenuation to baseline values. Fenoldopam mesylate improves cardiac output and lowers systemic vascular resistance with relative attenuation of pharmacodynamic effect during a 24-hour intravenous infusion.

Clinical relevance of long-term therapy with levodopa and orally active dopamine analogues in patients with chronic congestive heart failure

Beneficial effects of long-term treatment with dopamine analogues in patients with congestive heart failure may result from their vasodilating properties, in particular from renal artery vasodilation. Oral application of levodopa results in increased dopamine plasma levels and can improve cardiac performance and renal function in patients with congestive heart failure. A daily levodopa dosage of at least 4 g appears to a prerequisite for long-term response to the drug. Because of frequent side effects including nausea, vomiting, and dyskinesia at this dosage, the clinical usefulness of levodopa seems to be limited to a minority of patients. Ventricular arrhythmias have been shown to increase significantly during long-term levodopa therapy, probably due to stimulation of myocardial beta receptors. Increased ventricular arrhythmias or significant central nervous side effects have not been observed after administration of ibopamine and fenoldopam, which are orally active analogues of dopamine. Both agents exhibit potent arterial vasodilating properties and have been shown to increase cardiac performance in patients with congestive heart failure after short-term administration. The long-term beneficial effects of ibopamine and fenoldopam in the treatment of congestive heart failure have not yet been clarified. However, available results are encouraging and warrant further clinical evaluation of these agents, as well as the development of new analogues of dopamine, in particular of potent vascular dopamine agonists.

Dopamine-induced relaxation in human pulmonary arteries

Dose-dependent relaxations were induced by dopamine in human pulmonary arteries that had been contracted with prostaglandin F2 alpha without alpha-adrenergic blocking agents. The dopamine-induced relaxation was inhibited by haloperidol and fluphenazine, but not by domperidone, suggesting that this relaxation was mediated via DA1 receptors.

Vasodilator and inotropic drugs for the treatment of chronic heart failure: distinguishing hype from hope

During the past 10 years, more than 80 orally active vasodilator and inotropic agents have been tested in the clinical setting to evaluate their potential utility in the treatment of chronic heart failure. Although the initial reports of all of these drugs suggested that each represented a major therapeutic advance, only three agents--digoxin, captopril and enalapril--have produced consistent long-term hemodynamic and clinical benefits in these severely ill patients. Most of the other drugs that have been tested have not (to date) distinguished themselves from placebo therapy in large-scale, controlled trials, even though these agents produce hemodynamic effects that closely resemble those seen with digitalis and the converting-enzyme inhibitors. These observations suggest that the hemodynamic derangements that characteristically accompany the development of left ventricular dysfunction cannot be considered to be the most important pathophysiologic abnormality in chronic heart failure. Although cardiac contractility is usually depressed in this disease, positive inotropic agents do not consistently improve the clinical status of these patients. Similarly, although the systemic vessels are usually markedly constricted, drugs that ameliorate this vasoconstriction do not consistently relieve symptoms, enhance exercise capacity or prolong life. Hence, correction of the central hemodynamic abnormalities seen in heart failure may not necessarily provide a rational basis for drug development, and future advances in therapy are likely to evolve only by attempting to understand and modify the basic physiologic derangements in this disorder.

Cardiovascular and renal hemodynamic effects of intravenous infusions of the selective DA1 agonist, fenoldopam, used alone or in combination with dopamine and dobutamine

Fenoldopam (0.1 and 0.2 microgram/kg/min i.v.) was administered to pentobarbital-anesthetized dogs alone and combined with dopamine (DA) and dobutamine. Renal blood flow, heart rate, and mean arterial pressure were measured. Both dosages of fenoldopam increased renal blood flow without altering blood pressure, similar to the effects of DA (1 and 2 micrograms/kg/min). Administration of fenoldopam with only DA (1 microgram/kg/min) produced further increase in renal blood flow. After administration of phenoxybenzamine (15 mg/kg i.v.), DA produced significant increments in renal blood flow and reductions in renal vascular resistance when compared with experiments without phenoxybenzamine, suggesting even low dosages of DA exert alpha-adrenoceptor agonist activity. Dobutamine (2 and 4 micrograms/kg/min) increased renal blood flow about 37% of that produced by DA. Fenoldopam added to dobutamine produced similar increments in renal blood flow as DA. Fenoldopam did not affect the increase in cardiac contractile force produced by DA and dobutamine. Thus, fenoldopam alone or in combination with DA had no advantage over 2 and 4 micrograms/kg/min DA to further increase renal blood flow. In contrast, fenoldopam with dobutamine produced greater increments in cardiac contractile force than DA and equivalent increases in renal blood flow as DA.

Hemodynamic, renal, and neurohumoral effects of a selective oral DA1 receptor agonist (fenoldopam) in patients with congestive heart failure

Fenoldopam mesylate (SK&F 82526-J) is a novel benzazepine derivative. It has selective agonist activity at post-junctional (DA1) vascular dopaminergic receptors, which normally subserve renal artery vasodilation. Previous studies in normal subjects and in patients with hypertension indicate that fenoldopam increases renal blood flow and promotes a sodium diuresis. Drug efficacy was clinically evaluated in eight patients with chronic congestive heart failure (CHF) after a single oral dose of 100 mg of fenoldopam and following 3 days of therapy (100 mg four times daily). Stroke volume index acutely increased from 26 +/- 7 (mean +/- SD) to 30 +/- 4 ml/beat/m2 (p less than 0.05) and left ventricular filling pressure decreased from 26 +/- 13 to 23 +/- 11 mm Hg (p less than 0.05). Systemic vascular resistance decreased from 1513 +/- 159 to 1128 +/- 319 (p less than 0.05). Hemodynamic changes were seen as early as 30 minutes following fenoldopam and returned to control levels by 4 hours. Forearm blood flow, hepatic blood flow, and venous capacitance did not significantly change acutely, but renal blood flow index was significantly reduced (34 +/- 4 to 30 +/- 3 min-1 X 1000, p less than 0.01). Plasma norepinephrine, plasma renin activity, plasma arginine vasopressin, and plasma aldosterone did not significantly change acutely. After 3 days of treatment, 100 mg of fenoldopam again reduced the renal blood flow index (35 +/- 7 to 26 +/- 7 min-1 X 1000, p less than 0.01) and tended to increase plasma renin activity (11.7 +/- 8 to 21.2 +/- 19.4 ng/ml/hr, p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Continuous intragastric delivery of fenoldopam: relationship between plasma concentration and effects on renal function

1. The pharmacodynamics of the dopamine DA1 agonist fenoldopam were examined in six healthy male volunteers after constant intragastric infusions of fenoldopam at dosages of 0, 10, 25, 50 and 75 mg h-1 for 6 h. 2. Hourly p-aminohippurate (PAH) clearance was used to assess fenoldopam induced renal plasma flow changes. Marked dose-related increases in renal plasma flow were noted with a maximal increase of 65% over baseline values of 711 ml min-1 being seen at the 75 mg h-1 rate. No changes in sodium excretion and glomerular filtration rate were observed. 3. Mean steady-state fenoldopam plasma concentrations were related to mean PAH clearance based on an Emax model (r = 0.996) with an Emax of 1350 ml min-1 and an EC50 of 6.2 ng ml-1. 4. Mean steady-state plasma concentrations of fenoldopam-7-sulphate and fenoldopam-8-sulphate failed to increase with dose but were linearly correlated to mean PAH changes (r = 0.998, r = 0.981 respectively). 5. These results support the concept of extending fenoldopam's duration of action through the development of an oral sustained delivery system.

Intravenous fenoldopam in heart failure: comparing the hemodynamic effects of dopamine1 receptor agonism with nitroprusside

Dopamine1 receptors mediate hemodynamic effects that may be beneficial in patients with congestive heart failure. We infused the selective dopamine1 receptor agonist, fenoldopam mesylate (SKF 82526 J), to evaluate hemodynamic and neurohumoral changes during continuous intravenous infusion in patients with congestive heart failure and compared them with the effects of nitroprusside, a traditional vasodilator that works by a distinctly different mechanism. In 15 patients with a mean radionuclide ejection fraction of 17%, the agents were infused in a random-ordered, double-blinded, crossover, active drug-controlled protocol after optimal dosing was determined during a titration period. Hemodynamic changes were induced in minutes with both drugs during a mean (+/- standard deviation) infusion dose of 1.45 +/- 1.66 micrograms/kg/min for fenoldopam and 2.99 +/- 1.59 micrograms/kg/min for nitroprusside. At 1 hour, mean blood pressure decreased and cardiac index rose with both drugs, and the effect lasted throughout the 6-hour infusion period. Nitroprusside, but not fenoldopam, reduced right heart filling pressures (including mean pulmonary capillary wedge, mean right atrial, and mean pulmonary artery pressures) during the infusion period. Both drugs caused significant reduction in systemic vascular and pulmonary arteriolar resistances. No significant change occurred in plasma norepinephrine levels. Fenoldopam ameliorates some of the adverse hemodynamic changes that occur during heart failure but does not reduce right heart filling pressures as does nitroprusside. Because of fenoldopam's unique characteristics, it may benefit certain patients with heart failure.

Dopamine and new dopamine analogs: receptors and clinical applications

Division of dopamine (DA) receptors and alpha- and beta-adrenoceptors into two subtypes provides a pharmacological basis for the clinical use of DA and new DA receptor agonists in anesthesia and critical care medicine. First, differential receptor activation explains why three distinct cardiovascular and renal responses can be obtained at low, medium, and high infusion rates of DA. Low infusion rates, in which DA1 and DA2 receptors are activated, are being increasingly used to improve renal perfusion and to treat oliguric states. The medium dose range (activation of beta1-adrenoceptors) is used for treatment of heart failure. The high dose range (activation of alpha-adrenoceptors) is used for treatment of shock. Second, selective DA1 and relatively selective DA2 agonists and agonists with different combinations of DA and receptor activity other than DA have been synthesized and are being investigated for the treatment of congestive heart failure and hypertension. Some of these compounds could have advantages over DA for acute therapy. Future availability of these drugs in anesthesia and critical care settings will depend to a great extent on input from anesthesiologists concerning potential new uses and willingness to conduct clinical investigations.

Effects of fenoldopam, a specific dopamine receptor agonist, on blood pressure and left ventricular function in systemic hypertension

1. The effects of fenoldopam, an orally active, specific dopamine-1 receptor agonist, were studied in eleven patients with essential hypertension, using intra-arterial blood pressure recording and equilibrium gated radionuclide angiography. 2. A single dose of fenoldopam 100 mg produced a fall in blood pressure (BP) starting after 20 min. The maximum BP reduction (23/25 mm Hg) occurred after 50 min and was accompanied by a heart rate (HR) increase of 10 beats min-1. The acute effects on BP lasted for 130 min. 3. After 8 weeks of fenoldopam 100 mg, twice daily, only a small, statistically insignificant, hypotensive effect was still apparent after each dose of drug. The duration of the effect was too short to be clinically useful. Tilt-testing produced a BP fall of 24/14 mm Hg and a HR increase of 17 beats min-1. Three patients experienced symptoms of postural hypotension during the study. 4. The drug attenuated the blood pressure rise produced by dynamic cycle exercise and isometric hand grip. 5. Acute administration of fenoldopam increased the left ventricular ejection fraction from 61% to 71% (P less than 0.005) and increased the peak filling rate from 2.52 to 3.86 end diastolic vol s-1 (P less than 0.002). After chronic fenoldopam administration, the left ventricular ejection fraction was 65% (P = NS) pre-dose, rising to 69% (P less than 0.02) post-dose and the peak filling rate was increased from 2.7 to 3.38 end diastolic vol s-1 (P less than 0.01) 60 min post-dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Augmentation of renal blood flow and sodium excretion in hypertensive patients during blood pressure reduction by intravenous administration of the dopamine1 agonist fenoldopam

Activation of dopamine1 (DA1) receptors relaxes vascular smooth muscle, especially in the renal vascular bed. Fenoldopam, the first selective DA1-receptor agonist that can be administered to man, was infused intravenously in 17 patients with essential hypertension (mean blood pressure 152/101 mm Hg). It reduced blood pressure in a dose-dependent fashion at doses between 0.025 and 0.5 microgram/kg/min and the antihypertensive effect was sustained during 2 hr infusions. In 10 patients studied during free-water diuresis, fenoldopam increased renal plasma flow by 42%, glomerular filtration rate by 6%, and sodium excretion by 202%, while lowering mean arterial pressure by 12% (all p less than .05). Similar promotion of sodium excretion was observed during blood pressure reduction in six additional patients studied without water loading. Pronounced enhancement of renal function in spite of blood pressure reduction suggests that fenoldopam might have a special role in the treatment of patients with hypertension and renal impairment.

Stimulation of vascular dopamine receptors: status and future strategies

The ability to stimulate dopamine receptors in the heart and blood vessels with selective receptor agonists, such as fenoldopam, has been an important advance. Fenoldopam is a selective DA1 receptor agonist and is currently in clinical trials for cardiovascular disease therapy. An alternative approach to stimulating dopamine receptors, while at the same time blunting sympathetic nervous system activity, would be by inhibiting the enzyme dopamine beta-hydroxylase (D beta H), thus increasing the cardiovascular and renal ratio of dopamine to norepinephrine. SK&F 102698, (1-[3',5'-difluorobenzyl]-2-mercaptoimidazole), is a potent inhibitor of D beta H with a Ki of 40 nM against D beta H in vitro. In the spontaneously hypertensive rat SK&F 102698 100 mg/kg orally, increases the dopamine/norepinephrine ratio approximately 5-fold and lowers blood pressure approximately 30 mmHg to normotensive levels. Antihypertensive activity can be achieved with single daily oral administration and neither tolerance nor reflex tachycardia occur. Stimulation of dopamine receptors by inhibition of dopamine beta-hydroxylase is a unique approach toward cardiovascular and renal therapeutics.

Hemodynamic effects of selective dopamine receptor agonists in the rat and dog

The availability of highly selective dopamine receptor agonists has allowed the characterization of the role of DA1 and DA2 receptors in the cardiovascular system. Fenoldopam (SK&F 82526) is a potent agonist at DA1 receptors, with much less agonist activity at the DA2 subtype or at alpha and beta adrenoceptors. In contrast, SK&F 89124 activates only the DA2 subtype. SK&F 85174, the N-allyl derivative of fenoldopam, retains potent DA1 agonist activity but also has moderately potent agonist activity at the DA2 receptor. All three compounds will reduce blood pressure in hypertensive rats. In the anesthetized dog, each agonist will reduce blood pressure and total peripheral resistance. The overall hemodynamic profile is remarkably similar, despite the marked difference in dopamine receptor subtype selectivity. The principal pharmacologic difference is enhanced bradycardia with the compounds having DA2 agonist activity, resulting from activation of neuroinhibitory DA2 receptors on cardiac sympathetic nerve terminals. In the dog, each compound will increase renal blood flow. Studies in the anesthetized rat with fenoldopam and SK&F 89124, using radiolabelled microspheres to measure blood flow to various vascular beds, also show a significant increase in renal flow, with a tendency toward increased blood flow in the splenic and intestinal beds. Hence, dopamine receptor agonists offer a useful approach to cardiovascular therapy via DA1 mediated vascular dilation, DA2 mediated modulation of sympathetic tone or a combination of both activities.