Hemodynamic effects of PN 200-110 (isradipine) in congestive heart failure

Furazans in Medicinal Chemistry

Incorporation of heterocycles into drug molecules can enhance physical properties and biological activity. A variety of heterocyclic groups is available to medicinal chemists, many of which have been reviewed in detail elsewhere. Oxadiazoles are a class of heterocycle containing one oxygen and two nitrogen atoms, available in three isomeric forms. While the 1,2,4- and 1,3,4-oxadiazoles have seen widespread application in medicinal chemistry, 1,2,5-oxadiazoles (furazans) are less common. This Review provides a summary of the application of furazan-containing molecules in medicinal chemistry and drug development programs from analysis of both patent and academic literature. Emphasis is placed on programs that reached clinical or preclinical stages of development. The examples provided herein describe the pharmacology and biological activity of furazan derivatives with comparative data provided where possible for other heterocyclic groups and pharmacophores commonly used in medicinal chemistry.

Calcium antagonists

Calcium antagonists were introduced for the treatment of hypertension in the 1980s. Their use was subsequently expanded to additional disorders, such as angina pectoris, paroxysmal supraventricular tachycardias, hypertrophic cardiomyopathy, Raynaud phenomenon, pulmonary hypertension, diffuse esophageal spasms, and migraine. Calcium antagonists as a group are heterogeneous and include 3 main classes--phenylalkylamines, benzothiazepines, and dihydropyridines--that differ in their molecular structure, sites and modes of action, and effects on various other cardiovascular functions. Calcium antagonists lower blood pressure mainly through vasodilation and reduction of peripheral resistance. They maintain blood flow to vital organs, and are safe in patients with renal impairment. Unlike diuretics and beta-blockers, calcium antagonists do not impair glucose metabolism or lipid profile and may even attenuate the development of arteriosclerotic lesions. In long-term follow-up, patients treated with calcium antagonists had development of less overt diabetes mellitus than those who were treated with diuretics and beta-blockers. Moreover, calcium antagonists are able to reduce left ventricular mass and are effective in improving anginal pain. Recent prospective randomized studies attested to the beneficial effects of calcium antagonists in hypertensive patients. In comparison with placebo, calcium antagonist-based therapy reduced major cardiovascular events and cardiovascular death significantly in elderly hypertensive patients and in diabetic patients. In several comparative studies in hypertensive patients, treatment with calcium antagonists was equally effective as treatment with diuretics, beta-blockers, or angiotensin-converting enzyme inhibitors. From these studies, it seems that a calcium antagonist-based regimen is superior to other regimens in preventing stroke, equivalent in preventing ischemic heart disease, and inferior in preventing congestive heart failure. Calcium antagonists are also safe and effective as first-line or add-on therapy in diabetic hypertensive patients. Heart rate-lowering calcium antagonists (verapamil, diltiazem) may have an edge over the dihydropyridines in post-myocardial infarction patients and in diabetic nephropathy. Thus, calcium antagonists may be safely used in the management of hypertension and angina pectoris.

[Comparison of nicardipine and isradipine in hypertension following coronary artery bypass graft]

OBJECTIVE

Compare the efficacy of isradipine to that of nicardipine for the control of arterial hypertension following coronary artery bypass graft (CABG).

STUDY DESIGN

Clinical prospective, randomised study.

MATERIAL AND METHODS

40 patients ASA II or III, mean age 66 +/- 8 years, scheduled for elective CABG were included. If the mean arterial pressure (MAP) was > or = 100 mmHg within the first six post operative hours, the patients were included and randomly attributed to either one of the 2 groups: Gr I (n = 20) received nicardipine, Gr II (n = 20) received isradipine in bolus then in continuous perfusion. HR, MAP, MPAP, CVP, PCWP, CI, SVRI, PVRI and SVI were recorded at: T0 before administration of drugs, T1 = 2 min after the first bolus. T2 when MAP reached 85 +/- 5 mmHg. T3, T4, T5, T6, T7 and T8 at 5, 10, 30, 60, 90 and 120 min after the continuous perfusion. T9 before stopping the perfusion.

RESULTS

No significant changes in HR, CVP, PCWP, MPAP or PVRI at any time in both groups. Significant increase in CI at T2 in both groups. Reduction of MAP at T2 was more important (-27%) in Gr I compared to that in Gr II (-22%). This was mainly due to a significant decrease in SVRI.

CONCLUSION

Isradipine is effective in the treatment of arterial hypertension following CABG. However there is not any significant beneficial effect of isradipine over nicardipine.

Calcium channel blockers in cardiac failure

Congestive cardiac failure is an increasingly prevalent syndrome associated with a high morbidity and mortality. The role of calcium channel blockers in the treatment of heart failure is unclear. The potential benefits of these agents derive not only from their vasodilator properties, but also from anti-ischemic effects, beneficial effects on endothelial function and the development of atherosclerosis, and favorable effects on calcium cycling at a molecular level. Pitted against this array of potential benefits are direct negative inotropic effects and the potential for neuroendocrine activation. Treatment with short-acting dihydropyridine agents has not resulted in long-term clinical benefits in patients with cardiac failure. Diltiazem may be beneficial in patients with nonischemic heart failure, and verapamil has a neutral effect in cardiac failure, although it may have a role in combination with ace inhibition. To date, amlodipine has been associated with the most promising results, with evidence of a mortality benefit in nonischemic heart failure. Mibefradil is of no benefit in the management of heart failure, although the trend toward increased mortality in the treatment arm of the Mortality Assessment in Congestive Heart Failure (MACH)-1 trial may have been due to drug interactions. The potential role of calcium blockers in diastolic dysfunction and in combination with ace-inhibition requires further study.

The clinical significance of neurohormonal activation

Progressive heart disease after the onset of left ventricular dysfunction has typically been attributed to hemodynamic factors. As left ventricular function declines, decreased cardiac output and tissue hypoperfusion lead to compensatory increases in afterload, preload, and heart rate. The purpose of these compensatory responses is to increase cardiac output and maintain tissue perfusion; however, they may also create hemodynamic stress for the failing heart. However, this does not explain the progression of heart failure despite hemodynamic maintenance with pharmacologic therapy. Activation of neurohormonal systems that are essential for homeostasis in the normal heart plays a key role in the progression of heart failure. In acute heart failure, these systems have beneficial effects, but in chronic heart failure their activation produces deleterious effects by increasing the load on the left ventricle and promoting structural remodeling, which may further impair left ventricular function. The issue of neurohormonal activation is an important one in cardiovascular medicine, not only for patients with heart failure but also for patients with hypertension and ischemic heart disease when left ventricular dysfunction is present. As neurohormonal activation may play a pathogenic role in the long-term outcome of patients, interventions that have favorable hemodynamic but unfavorable neurohormonal effects can actually exacerbate cardiac disease and may increase cardiovascular morbidity and mortality. As neurohormonal activation appears to parallel the severity of heart failure, whether assessed according to symptoms or prognosis, an understanding of neurohormonal activation and its interaction with hemodynamic factors is essential for optimizing pharmacologic therapy for cardiovascular disease.

Cardiac effects of calcium antagonists in systemic hypertension

The calcium antagonists are a class of heterogeneous drugs, with a wide spectrum of direct and indirect cardiac effects that vary a great deal from one drug to another and depend upon formulation and duration of action. Calcium antagonists act by decreasing total peripheral resistance to lower arterial pressure. As a consequence, reflex tachycardia, increased cardiac output, and increased plasma catecholamine and plasma renin activity are commonly seen, particularly with the initial dose and with short-acting dihydropyridines. The abrupt vasodilation can paradoxically elicit angina and even acute myocardial infarction. These hemodynamic and neuroendocrine changes are less pronounced with the long-acting formulations. Most calcium antagonists diminish automaticity of the sinus node, slow conduction in the atrioventricular node, and have little, if any, effect on the automaticity of the myocytes. The dihydropyridines generally have less effect on automaticity and cardiac conduction than nondihydropyridines. The negative inotropic effect is most profound with nondihydropyridines and is greatly reduced or absent with newer dihydropyridines, such as isradipine, felodipine, amlodipine, and nisoldipine. Long-acting calcium antagonists generally improve myocardial oxygenation by unloading the heart, increasing coronary blood flow, and reducing myocardial oxygen consumption. Thus, calcium antagonists have a variety of beneficial effects in patients with hypertensive heart disease: they reduce left ventricular hypertrophy and its sequelae, such as ventricular dysrhythmias, impaired filling and contractility, and myocardial ischemia. Ongoing studies should provide a more conclusive answer regarding the efficacy and safety of calcium antagonists.

Comparative study of elgodipine and nisoldipine on the contractile responses of various isolated blood vessels

The effects of elgodipine, a new dihydropyridine derivative, were compared to those of nisoldipine on contractile responses in various isolated artery rings and on mechanical activity in portal vein segments. Arteries used were: rabbit aorta, mesenteric (fifth branch), femoral and basilar, and sheep coronary arteries. Elgodipine and nisoldipine (10(-16)-3 x 10(-6) M) produced a concentration-dependent inhibition of the contractile responses induced by high K+ (80 mM), 5-hydroxytryptamine (10(-5) M) or noradrenaline (10(-6) M or 10(-4) M) in all the arteries studied. The inhibitory effect of elgodipine was greater in mesenteric resistance vessels (IC50 = 8.0 +/- 2.1 x 10(-12) M and 2.0 +/- 0.5 x 10(-13) M for the depression of high K(+)- and agonist-induced contraction, respectively), and in coronary arteries (IC50 = 2.6 +/- 0.3 x 10(-10) M and 9.0 +/- 1.4 x 10(-8) M for the inhibition of high K(+)- and agonist-induced contraction, respectively). In addition, the action of elgodipine in peripheral resistance vessels and in the coronary artery was more prominent than in aorta or femoral arteries, and this tissue selectivity was more apparent for elgodipine than for nisoldipine. In rat portal vein elgodipine (IC50 = 6.5 +/- 0.9 x 10(-8) M) and nisoldipine (IC50 = 8.5 +/- 1.3 x 10(-8) M) reduced in a concentration-dependent manner the development of mechanical activity. Furthermore, contractile responses produced by the addition of Ca2+ (1-5 mM) to Ca(2+)-free high K+ solution were also concentration dependently inhibited by elgodipine. However, elgodipine did not modify noradrenaline-induced contractions attributed to intracellular Ca2+ release. The results of this study indicate that elgodipine has potent vasodilator properties and vascular selectivity. The mechanisms through which elgodipine relaxes vascular smooth fibres seem to be related to its ability to inhibit the entry of extracellular Ca2+ into the cell.

Isradipine decreases exercise-induced albuminuria in patients with essential hypertension

The aim of our study was to investigate the effects of exercise on albuminuria and blood pressure in patients with essential hypertension, and the short-term effect of the calcium channel blocker isradipine on exercise-induced albuminuria (UAE) and blood pressure in the same patients. Ten patients (7 males, 3 females) with essential hypertension were admitted to the study. The mean age was 54 +/- 2.7 years and the mean body mass index was 27 +/- 1 kg/m2. Patients performed two physical exercise tests on a cycloergometer. Workload was increased by 30 watts every 2 min until 90% of the theoretical maximal heart rate was achieved. This workload was maintained for 5 min. Samples for albuminuria assay were collected at the end of exercise and 1 h after exercise. The first physical exercise test was performed after 15 days of placebo washout; the second exercise was performed after 10 days of therapy with isradipine 5 mg once daily p.o. After 10 days of therapy with isradipine, UAE immediately after (31 +/- 8.3 micrograms/min) and 1 h after exercise (31.5 +/- 7.3 micrograms/min) were significantly (p < 0.05) lower as compared to the values found after placebo (37.1 +/- 9.3 micrograms/min; 43.5 +/- 9.9 micrograms/min). Our data show that short-term administration of the calcium channel blocker isradipine is able to cause a concomitant significant decrease in exercise-induced pressor and albuminuric response in patients with essential hypertension. The finding that short-term calcium channel blockade can reduce exercise-induced albuminuria in essential hypertensive patients suggests that progression of nephropathy in this early phase could be slowed by isradipine in these patients.

Isradipine--another calcium-channel blocker for the treatment of hypertension and angina

OBJECTIVE

To review the pharmacology, pharmacokinetic disposition, dose recommendations, adverse effects, drug interactions, and efficacy of isradipine in patients with hypertension or ischemic heart disease.

DATA SOURCES

Data from scientific literature were extracted, evaluated, and summarized for presentation. A MEDLINE search was conducted using the following indexing terms: isradipine, calcium-channel blockers, hypertension, and angina pectoris. Experiences from studies evaluating isradipine reported in the form of articles, abstracts, or proceedings involving patients or healthy subjects were considered for inclusion.

STUDY SELECTION

Special consideration was given to clinical studies that had been designed in a blind, randomized fashion. Studies that compared the effectiveness and safety of isradipine with another antihypertensive or antianginal agent or placebo were included.

DATA EXTRACTION

Data from human studies published in the English language were evaluated. Trials were evaluated according to sample size, design, and adequacy of description of therapeutic response.

DATA SYNTHESIS

Isradipine is a new dihydropyridine calcium-channel blocker that appears to exert less negative inotropic activity than nifedipine and to selectively inhibit sinoatrial conduction. Pharmacokinetic parameters are quite variable and considerably more work is needed to better describe the kinetic disposition of isradipine. Antihypertensive efficacy has been demonstrated extensively in a number of short-term trials. Antianginal efficacy also has been observed in a few short-term trials and is comparable to that of isosorbide dinitrate and nifedipine. Extensive experience with isradipine is minimal and no clear-cut advantages over existing compounds have been noted thus far.

CONCLUSIONS

The place of isradipine in the therapy of hypertension and myocardial ischemia is unclear and its routine use cannot yet be recommended based solely on clinical grounds.

Comparison of isradipine with nitroprusside for control of blood pressure following myocardial revascularization: effects on hemodynamics, cardiac metabolism, and coronary blood flow

The effects of isradipine (ISR) on cardiac performance, myocardial metabolism, and coronary blood flow were compared with those of sodium nitroprusside (SNP) when used to control blood pressure following myocardial revascularization. Twenty patients were randomized to receive either intravenous ISR or SNP if arterial blood pressure increased above 130 mm Hg systolic. Hemodynamic and metabolic parameters were studied using radial, pulmonary arterial, and coronary sinus catheters. Cardiac output and coronary blood flows were measured by thermodilution and blood was taken for calculation of myocardial oxygen consumption and lactate extraction. Electrocardiographic changes were recorded by Holter monitoring throughout the study. ISR and SNP both produced a satisfactory reduction in blood pressure accompanied by a decreased systemic vascular resistance (P less than 0.001). ISR infusion was associated with increases in cardiac output and stroke index (P less than 0.01), which were not apparent in the SNP group. Tachycardia occurred with SNP (P less than 0.01) but not with ISR therapy. Right and left ventricular stroke work indices and myocardial oxygen consumption were reduced with SNP. The ISR group showed unchanged myocardial oxygen consumption with increased right ventricular stroke work index. Coronary vascular resistance decreased (P less than 0.01) during ISR infusion but decreased only slightly in the SNP group. Great cardiac vein blood flow was significantly increased with ISR but not with SNP, resulting in a significant difference between the groups (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiovascular effects of isradipine in essential hypertension

The immediate and short-term cardiovascular effects of oral isradipine therapy were evaluated in 11 patients with mild to moderate systemic hypertension. Isradipine, 5 mg administered orally, induced a significant reduction in arterial pressure from 165 +/- 6/88 +/- 3 mm Hg to 140 +/- 5/76 +/- 2 mm Hg (p less than 0.001) within 2.5 hours by a decrease in total peripheral resistance associated with an increase in heart rate and cardiac output. Contrary to the acute effect, oral therapy with isradipine for 3 months reduced arterial pressure through a decrease in total peripheral resistance but without causing an increase in heart rate or cardiac output or activation of the sympathetic nervous system. Isradipine slightly reduced left ventricular mass and improved cardiac systolic function and left ventricular filling. Renal blood flow increased, and renal vascular resistance (p less than 0.01) and total blood volume (p less than 0.002) decreased without a change in either sodium excretion or body weight. Thus, isradipine, when given for 3 months, decreased arterial pressure by reducing total peripheral resistance without activation of reflexive mechanisms. Its favorable effects on systemic hemodynamics, total blood volume, renal blood flow, and cardiac structure and function suggest isradipine to be an excellent choice for antihypertensive therapy.

Isradipine

Isradipine is a potent dihydropyridine calcium channel blocker. It is highly selective for vascular smooth muscle, with very few negative inotropic or chronotropic effects. It may have minor depressant effects on the sinoatrial node, hence reducing the incidence of reflex tachycardia. The drug is extensively metabolized in the liver, with several pharmacologically inactive metabolites. As the elimination half-life is about 9 h the drug is usually given twice daily, but a once-daily modified release form is under investigation. Isradipine is effective monotherapy in essential hypertension, and has been successfully combined with pindolol and captopril. On the basis of more limited evidence it also appears to be beneficial in stable angina and in congestive cardiac failure. A trial is also under way to assess its antiatherogenic properties. Adverse effects are those predicted for a vasodilator calcium antagonist, and may be less frequent than for equivalent doses of nifedipine. This needs to be confirmed by more extensive clinical experience. Overall, isradipine can be considered favourably in essential hypertensives where a calcium channel blocker is indicated, particularly if it is desirable to avoid myocardial depression or to minimize reflex tachycardia. Its role in other cardiovascular disease awaits further evaluation.

Different negative inotropic activity of Ca2(+)-antagonists in human myocardial tissue

To evaluate the negative inotropic effect of various Ca2(+)-antagonists in human myocardium without additional influences of preload, afterload, or frequency, we examined their effects on isometric force of contraction in isolated human papillary muscle strips and in auricular trabeculae. The 1,4-dihydropyridines isradipine, nitrendipine, and nifedipine, the phenylalkylamine verapamil, and the benzothiazepine diltiazem exerted concentration-dependent negative inotropic effects. The potency of the investigated Ca2(+)-antagonists was identical in papillary muscle strips of patients with only moderate clinical signs of heart failure undergoing mitral valve replacement-operation (NYHA II-III) and in terminally failing (heart transplantation, NYHA IV) human hearts. The IC50 values were lower in auricular trabeculae than in papillary muscle strips. The difference was significant for nifedipine, nitrendipine, and verapamil. The restorative effects of external Ca2+ after pretreatment with Ca2(+)-antagonists were significantly less strong after pretreatment with 1,4-dihydropyridine than with non-dihydropyridines in papillary muscle strips. It is concluded that 1,4-dihydropyridines and verapamil and diltiazem did differently influence Ca2(+)-mediated increase in force of contraction. Moreover, a relation between the therapeutically active free plasma concentration in vivo and the negative inotropic potency in vitro can be found. This relation follows a rank order of potency for negative inotropism (isradipine less than or equal to nitrendipine less than diltiazem less than nifedipine less than verapamil) and might have clinical relevance in the treatment of patients with compromised cardiac function.

The pharmokinetics of isradipine in hypertensive subjects

In conjunction with a multicentre clinical trial of the calcium antagonist isradipine in hypertension, pharmacokinetic and pharmacodynamic studies were conducted in 9 subjects. An initial dose of 5 mg (capsule formulation) of isradipine was given orally. The mean Cmax, tmax and AUC(0-8) were 6.0 ng.ml-1, 1.5 h and 15.1 h.ng.ml-1 respectively. Seven subjects repeated the study at steady state after 10 week's dose titration with isradipine. Cmax, tmax and AUC(0-8) were 3.7 ng.ml-1, 1.2 h and 12.2 h.ng.ml-1 respectively indicating that the drug does not accumulate over time. Control of blood pressure paralleled plasma isradipine concentrations which suggested that the drug should be given at least twice daily. Pharmacokinetic studies performed in conjunction with clinical trials can provide valuable information about the patterns of drug response.

Effects of intravenous isradipine on left ventricular performance during rapid atrial pacing in coronary artery disease

The effects of isradipine, a new dihydropyridine calcium antagonist, were evaluated in 24 patients referred for elective cardiac catheterization because of suspected coronary artery disease. Hemodynamics and left ventricular (LV) function (by digital subtraction angiography) were measured at baseline and during rapid atrial pacing (mean peak heart rate 135 beats/min), which induced chest pain or electrocardiographic changes in all patients. After a control pacing period, intravenous isradipine (0.01 mg/kg, n = 16) or placebo (n = 8) was administered in a double-blind fashion and all variables were measured again at baseline and during pacing to the same maximum heart rate. Before isradipine was given, pacing had no effect on systolic blood pressure, while increasing diastolic blood pressure (68 +/- 8 to 87 +/- 11 mm Hg, p less than 0.0001) and LV end-diastolic pressure measured in the immediate postpacing period (13 +/- 5 to 18 +/- 6 mm Hg, p less than 0.03) and decreasing LV end-diastolic volume index (59 +/- 18 to 40 +/- 12 ml/m2, p less than 0.001), stroke volume index (37 +/- 11 to 23 +/- 10 ml/m2, p less than 0.0001), ejection fraction (0.64 +/- 0.07 to 0.53 +/- 0.12, p less than 0.0003) and percent regional shortening in 4 of 5 myocardial wall segments. During pacing after isradipine, systolic and diastolic blood pressures were lower, ejection fraction was higher and percent regional shortening decreased in only 2 of 5 myocardial segments. In comparison to placebo, isradipine increased baseline heart rate, ejection fraction and stroke volume index while it decreased arterial pressure and end-systolic volume index before the second pacing period.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic response, safety, and efficacy of isradipine in the treatment of essential hypertension

The hemodynamic response achieved by isradipine is balanced; there is a marked decrease in total peripheral resistance with no clinically significant tachycardia or cardiodepressant effect, no fluid retention (natriuretic/diuretic effect) or orthostatic reactions, whereas the blood flow to vital organs is preserved. The blood pressure-lowering effect of isradipine as monotherapy is dose dependent and has shown a greater efficacy than propranolol, hydrochlorothiazide, and prazosin, without an increase in adverse effects. Combination therapy with a beta-blocker is also safe and offers a useful additional reduction in blood pressure. Indeed, the side effects are no more frequent than with placebo (in doses below 10 mg daily); they are also dose dependent and appear to diminish with time. Isradipine's antiatherogenic effects and cardiac protection potential require further evaluation in clinical studies, but add an interesting aspect to the drug. Against this background, isradipine appears to be a useful addition to our therapeutic arsenal and has the potential to become the drug of choice in the treatment of hypertension.

Hemodynamic study of short- and long-term isradipine treatment in patients with chronic ischemic congestive heart failure

The acute hemodynamic effects of isradipine on cardiac performance, at rest and during exercise, were examined in nine male patients aged 37 to 69 years with congestive heart failure due to ischemic heart disease. The effects of 10 mg oral isradipine were maximal after two to three hours with significant decreases in blood pressure as well as in systemic and pulmonary vascular resistances, and an increase in cardiac output. There were no significant changes in heart rate or pulmonary capillary wedge pressure. For the same 50-watt bicycle workload pre- and post-drug, the addition of isradipine was associated with lower systemic and pulmonary vascular resistances (systemic vascular resistance, 805 +/- 70 versus 975 +/- 70; p less than 0.01; pulmonary vascular resistance, 144 +/- 27 versus 207 +/- 35 dynes.sec.cm-5; p less than 0.01), and lower pulmonary artery pressures (54 +/- 6/23 +/- 3 versus 66 +/- 7/27 +/- 3 mm Hg; p less than 0.01) during exercise. In a double-blind 12-week trial, body weight decreased during isradipine treatment (71.6 to 68.9 kg; p less than 0.01), but there were no significant changes in exercise duration, radionuclide ejection fraction, or cardiothoracic ratio, and no serious side effects were encountered. These results suggest that isradipine is worthy of further evaluation in long-term treatment of chronic ischemic congestive heart failure.

Calcium antagonists in hypertension

The calcium antagonists are effective and safe agents for the treatment of arterial hypertension. They are well tolerated by the patients. In contrast to other types of antihypertensive agents, they cause few metabolic disturbances. They can be combined with diuretics, beta-blockers, and angiotensin-converting enzyme (ACE) inhibitors. They can be safely prescribed to patients with hypertension and concomitant diseases such as diabetes mellitus, chronic obstructive lung disease, congestive heart failure, gout, renal failure, peripheral atherosclerotic disease, or Raynaud's phenomenon. Dietary sodium restriction during antihypertensive therapy with calcium antagonists is not required for optimal antihypertensive efficacy. The second generation of calcium antagonists especially the dihydropyridine analogues that have greater potency and vascular selectivity, and a longer duration of action, will optimize the treatment of hypertension. Their antiatherosclerotic, antiplatelet, and "antitrophic" effects in experimental models for atherogenesis and hypertension hold great promise for the future since, so far, there has been no major success in reducing the incidence of coronary death by the treatment of hypertension.

Calcium antagonists and heart failure

The systemic vasodilatory actions of the calcium antagonists make them potentially attractive for use as afterload reducing agents in patients with left ventricular failure. However, unlike other vasodilator drugs, these drugs also exert a direct negative inotropic effect on the myocardium. Clinical data suggest a limited role for the calcium antagonists as vasodilator therapy in patients with heart failure.

Calcium channel antagonists. Part V: Second-generation agents

Second-generation agents include new dihydropyridines, such as amlodipine, felodipine, isradipine, nicardipine, nimodipine, nisoldipine, and nitrendipine. Verapamil-like agents include tiapamil, gallopamil, and anipamil. Among the diphenylalkylamines, bepridil is of special interest. New preparations of existing agents include slow-release formulations of nifedipine, verapamil, and diltiazem. From all these agents will be selected those that are longer-acting and provide higher vascular selectivity.

Acute hemodynamic effects of intravenous isradipine

The acute hemodynamic effects of isradipine, a new dihydropyridine calcium antagonist, were evaluated in 16 men referred for elective cardiac catheterization. Low-dose (0.007 mg/kg, n = 8) and high-dose (0.015 mg/kg, n = 8) isradipine was administered intravenously over 10 minutes and the hemodynamic alterations assessed 10 minutes after completion of infusion. Low-dose isradipine caused increases in heart rate (68 +/- 9 to 79 +/- 12 beats/min, p less than 0.001) (mean +/- standard deviation), cardiac index (3.0 +/- 0.7 to 4.1 +/- 0.9 liter/min/m2, p less than 0.001) and coronary sinus blood flow (114 +/- 27 to 162 +/- 74 ml/min, p less than 0.01), and significant decreases in mean aortic pressure (104 +/- 17 to 92 +/- 10 mm Hg, p less than 0.01), systemic and coronary vascular resistance. High-dose isradipine caused similar effects: the heart rate increased (72 +/- 6 to 84 +/- 14 beats/min, p less than 0.005), as did the cardiac index (3.0 +/- 0.6 to 4.6 +/- 0.9 liter/min/m2, p less than 0.001) and coronary sinus blood flow (122 +/- 48 to 166 +/- 47 ml/min, p less than 0.025). In addition, there were increases in the stroke volume index (43 +/- 10 to 55 +/- 8 ml/m2, p less than 0.001) and left ventricular stroke work index (69 +/- 12 to 79 +/- 12 g-m/m2, p = 0.05) after the high-dose infusion. Vascular resistance declined significantly in the systemic, pulmonary and coronary beds.(ABSTRACT TRUNCATED AT 250 WORDS)

Usefulness of calcium antagonists for congestive heart failure

In patients with congestive heart failure (CHF) due to dilated cardiomyopathy, nifedipine, diltiazem and several of the newer calcium antagonists including nicardipine, nitrendipine, felodipine and PN 200-110 (isradipine) improve left ventricular function. Because of its relatively more pronounced negative inotropic and chronotropic actions, verapamil is generally not tolerated by patients with left ventricular failure. In addition, even relatively vascular-selective agents such as nifedipine can occasionally cause significant left ventricular depression, particularly if combined with beta-adrenergic blocking agents. Comparative studies using nitroprusside to cause an equivalent decrease in arterial pressure indicate that nifedipine acts predominantly on the arterial vasculature, and that a small but significant decrease in contractility occurs, apparently due to a direct myocardial action. Although diltiazem causes a depression in myocardial contractility in dogs with volume overload heart failure, limited data show no significant negative inotropic action in patients with heart failure. The negative inotropic effects, if any, of newer and possibly more vascular-selective agents are not yet known. Calcium antagonists appear to act predominantly on the limb and coronary vasculature, with relatively less effect on renal and hepatic vessels. In patients with CHF, nifedipine causes an increase in coronary blood flow and a decrease in the aorto-coronary sinus oxygen difference indicating an improvement in myocardial energetics. Although nifedipine causes an increase in cardiac index and decreases in systemic vascular resistance and pulmonary capillary wedge pressure during exercise, the limited data available fail to show a short- or long-term increase in exercise capacity. Nifedipine causes an increase in plasma renin activity, possibly due to a direct action on the kidney.(ABSTRACT TRUNCATED AT 250 WORDS)