The Long-Term Efficacy of Ibopamine in Treating Patients with Severe Heart Failure

Risk factors for mortality in users of ibopamine

AIMS

In September 1995, the indication for the oral dopamine agonist ibopamine was restricted in the Netherlands and in several other European countries to patients with NYHA-class II heart failure as a result of an interim analysis of the PRIME-II trial. This trial demonstrated an increased risk of mortality in patients with NYHA-class III/IV heart failure on ibopamine. In September 1995, we initiated an assessment of the effects of ibopamine under everyday circumstances in a cohort of users of ibopamine in all NYHA-classes.

METHODS

In a nationwide retrospective cohort study all 2147 community pharmacies and drug dispensing general practitioners received a request to list all patients to whom they had dispensed ibopamine in the preceding years. All responding drug dispensing outlets (DDO) received a questionnaire on cardiovascular risk factors and mortality for the general practitioner of a random sample of these patients. DDO were also requested to send an anonymised printout of the complete medication record. On the end-date of follow-up, February 15th 1996, mortality rates were compared across categories of ibopamine use, adjusted for potential confounders. To assess medication use, drug exposure was compared in a 3 months' period before date of death in the deceased, and before a random date in those patients who were still alive.

RESULTS

In patients with NYHA-class III/IV heart failure, multivariate analysis indicated that current use of ibopamine was significantly associated with mortality (RR 1.37;95% CI: 1.15-1.64). In patients with NYHA-class I/II heart failure, however, multivariate analysis showed a 2.03 (95% CI: 1.10-3.72) risk of mortality in current users of ibopamine. Apart from current use of ibopamine, male gender and increased serum creatinine were also independent risk factors for mortality in all NYHA-classes. No statistically significant association was found between mortality and current use of amiodarone or use of amiodarone at baseline.

CONCLUSIONS

The increased risk of mortality in patients with NYHA-class III and IV heart failure on ibopamine seems to confirm the main finding of the recently published PRIME-II trial. However, our results indicate that also patients with NYHA-class I/II heart failure may be at an increased risk of mortality when using ibopamine. Additional research on the effects of ibopamine in these patients is warranted and the use of ibopamine in NYHA-class II heart failure patients may have to be reconsidered.

Clinical efficacy of ibopamine in patients with chronic heart failure

Ibopamine, the most widely studied dopaminergic drug for the treatment of chronic heart failure, appears to have beneficial hemodynamic, renal, and neurohormonal effects in this setting. Angiotension-converting enzyme (ACE) inhibitors have become the recommended standard treatment for chronic heart failure; however, some patients may benefit from additional drugs to improve their symptoms and functional capacity. Ibopamine may be effective as an additive drug for patients with chronic heart failure. It is also possible that ibopamine will improve survival in these patients. Large-scale trials are needed to assess the effects on morbidity and mortality when ibopamine is added to ACE inhibitors, diuretics, and possibly digitalis.

Neurohormonal and hemodynamic effects of ibopamine

Ibopamine is the prodrug of epinine or N-methyl dopamine. Ibopamine stimulates the DA1 and DA2 dopaminergic receptors, the beta 1 and beta 2 adrenoceptors, and the alpha 1 and alpha 2 adrenoceptors. Ibopamine has varying degrees of affinity for these various families, being the highest for the dopamine receptors and the lowest for the alpha adrenergic receptors. In the clinical setting, there is a dose-related hemodynamic and neurohormonal response. In patients with heart failure (HF), low doses appear to exert beneficial neurohormonal, hemodynamic, and renal effects, without increased inotropic effects. However, at higher doses (> 200 mg) ibopamine exerts effects that do not appear to be clinically useful in long-term treatment of chronic HF. Several small trials have suggested a benefit of ibopamine on exercise performance in patients with mild to moderate HF. On the basis of these studies, ibopamine is now being used in Europe to treat patients with mild to moderate congestive heart failure (CHF). At doses of 100 or 200 mg/t.i.d., there has been no evidence of significant safety problems. Ibopamine may have a role in the treatment of patients with more severe left ventricular dysfunction who remain symptomatic despite therapy with diuretics and angiotensin-converting enzyme (ACE) inhibitors. Preliminary data suggest the drug is well tolerated in this setting and can decrease sympathetic stimulation. Large placebo-controlled trials will assess the benefits of the optimal dose of the drug when added to ACE-inhibitor therapy, and the effect on survival.

The effects of oral ibopamine in patients with mild heart failure--a double blind placebo controlled comparison to furosemide. The Ibopamine Study Group

The effect of ibopamine and furosemide in 130 patients with NYHA Class I and II heart failure were studied in a parallel, double-blind, randomized placebo-controlled multi-centre trial. Ibopamine 200 mg b.i.d. was compared to furosemide 40 mg q.d. and placebo. A 1- to 2-week single-blind run-in period was followed by an 8-week double-blind treatment period. Reproducible treadmill exercise test times with the modified Naughton-Balke protocol were required for randomization. Exercise times increased significantly in comparison to the placebo group after 8 weeks of therapy for both the furosemide group (1.2 min, P < 0.035) and the ibopamine group (1.3 min, P < 0.025). Neither furosemide nor ibopamine affected quality of life assessments. Adverse clinical experiences were generally mild and similar in frequency amongst the three treatment groups. The results of this study show the usefulness of both ibopamine and furosemide as monotherapy in patients with mild congestive heart failure.

Effects of acute and chronic ibopamine administration on resting and exercise hemodynamics, plasma catecholamines and functional capacity of patients with chronic congestive heart failure

The effects of acute and chronic ibopamine treatment on resting and exercise hemodynamics, exercise capacity and plasma catecholamines were evaluated in 25 patients with chronic heart failure, using a double-blind, parallel, placebo-controlled design. During 2 months of therapy with either placebo or ibopamine (100 mg, 3 times daily), 1 patient was withdrawn from each group for worsening heart failure, New York Heart Association functional class improved in 4 patients on ibopamine and in 1 on placebo, and furosemide dose could be decreased in 4 on ibopamine and in no patient on placebo. Acute ibopamine administration induced, in comparison with placebo, a significant increase of cardiac and stroke volume indexes both at rest and peak exercise, with a reduction of systemic vascular resistance. These hemodynamic changes were maintained also after chronic therapy, with no evidence of tolerance development. Exercise capacity (evaluated as peak exercise duration and oxygen consumption, and ventilatory threshold) did not significantly change. Resting and peak exercise norepinephrine plasma levels were significantly reduced after both acute and chronic ibopamine administration. Thus, the hemodynamic and neurohumoral effects of ibopamine make this drug potentially useful for the chronic treatment of congestive heart failure.

Current status of non-digitalis positive inotropic drugs

Considerable effort and resources have been directed at the development and study of positive inotropic drugs over the past 10-15 years. Much has been learned about the physiology and pharmacology of myocardial contraction, the application of agents to augment contractility, and, importantly, the general and specific limitations of positive inotropic therapy. Studies on acute inotropic intervention have now shown that a drug's ability to augment overall cardiac performance is heavily dependent on its effects on vasculature, vascular control, and ventricular-vascular coupling. The clinical research on new agents has served to remind us how difficult it is to formulate the "ideal" positive inotropic or cardiovascular support drug for the critical care setting. The vast effort to develop a chronically and orally administrable drug to replace or even supplement digitalis has generally been disappointing. The dopaminergic agents (e.g., ibopamine, levodopa) act primarily via vasodilation and their effectiveness and role in managing heart failure remain unresolved. The initial excitement about the phosphodiesterase III inhibitors (e.g., amrinone, milrinone, enoximone) has been tempered by the results of large well-designed trials indicating variable effectiveness and a prominent adverse effect profile. During long-term oral administration none of these agents has been shown to improve clinical status or exercise capacity beyond that achieved by digoxin, when administered either separately or in combination with digoxin. The Prospective Randomized Milrinone Survival Evaluation (PROMISE) trial, showing that repeated oral administration of milrinone can increase mortality in heart failure, is having a devastating effect on the further development of this class of drugs.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy of ibopamine in the treatment of heart failure

Loss of myocardial contractility, reflexly enhanced vasoconstriction, and neuroendocrine excitation are the pathophysiologic hallmarks of low-output heart failure. Drugs that counter both consequences afford considerable therapeutic potential in retarding and perhaps even in staying the consequences of the syndrome. Ibopamine possesses such potential through its unique ability to stimulate both dopaminergic- and beta-adrenoreceptors in the heart and circulatory system. Stimulation of dopaminergic- receptors and beta 2-adrenoreceptors results in vasodilatation in all regional vascular territories. beta 2-Adrenoreceptor agonist activity also affords mild positive inotropic activity in the heart, whereas stimulation of presynaptic dopaminergic- receptors (DA2) attenuates the increased sympathetic neural outflow. The drug also suppresses the renin-angiotensin-aldosterone system in addition to having a direct natriuretic activity. The pharmacodynamic effects of ibopamine, exerted through its metabolite epinine, are translated into measurable therapeutic benefits in patients with chronic heart failure. The increase in peripheral blood flow induced in all regional vascular territories, including the kidneys, is associated with increased cardiac output and stroke volume and reduction in left ventricular pressure work, wall stress, and myocardial oxygen consumption. Plasma norepinephrine, angiotensin, and aldosterone are also reduced, and renal sodium excretion is enhanced. These hemodynamic and neuroendocrine activities, which are not subject to tolerance during sustained administration of the drug, are accompanied by clinically significant improvement in symptoms, exercise tolerance, and the New York Heart Association classification of disability. More important, no proarrhythmic effects have been observed during sustained treatment, and the minimal side effects observed during long-term treatment enhance the safety profile of the drug.(ABSTRACT TRUNCATED AT 250 WORDS)

How to select a drug for the long-term treatment of chronic heart failure

First-line drugs for the treatment of chronic congestive heart failure should produce immediate symptomatic benefit, improve exercise tolerance, and thereby improve the quality of life. They should preferentially be active as monotherapy or at least reduce the need for comedication. The drugs must be safe and well tolerated by patients and change, in the end, the natural history of the disease, so that sudden death will be prevented and life expectancy improves. None of the currently available drugs satisfies all these criteria. Diuretics, digitalis, converting-enzyme inhibitors, and ibopamine come close to the described ideal.