Acute haemodynamic effects of a new calcium antagonist, nicardipine, in man. A comparison with nifedipine

Factors affecting outcome of intracerebral hemorrhage in patients undergoing chronic hemodialysis

To date, despite a markedly high incidence of intracerebral hemorrhage (ICH) in patients with end-stage renal disease, only few studies have focused on factors that affect patient's prognosis. To elucidate these factors, we retrospectively investigated 22 consecutive patients who had chronic renal failure, were maintained by hemodialysis (HD), had suffered from ICH, and were hospitalized and treated in our institute from 2006 to 2008. Hematoma volume, blood pressure on admission, blood pressure 3 days after ICH onset, and neurological deterioration significantly affected patient mortality. Progression of neurological symptoms during HD was observed often in patients with hematoma of more than 60 mL or in patients with pontine hemorrhages. Age, gender, duration of HD, anti-platelet or anticoagulant therapies, or maximal dose of nicardipine did not affect patient's prognosis. Based on this study we conclude that controlling blood pressure on admission and within 3 days after onset of ICH may be the most important factor that would improve patient's prognosis. Further, special care might be required for patients with large hematomas (more than 60 mL) or those with brainstem hemorrhages, because progression of neurological symptoms occurs often in such patients.

Calcium channel blockade: central hemodynamic effects

Despite differences in vasodilatation, inotropy and chronotropy between verapamil, nifedipine and diltiazem when tested in vitro, these drugs will produce similar central hemodynamic effects in healthy young or middle-aged individuals, provided they are given in equipotent doses. The individual profiles of hemodynamic action of these calcium channel blockers are briefly reviewed and discussed.

Pre-PTCA detection of chronic but reversible postischemic myocardial dysfunction by nicardipine

The aim of the study was to find out whether in patients (n = 24) with one-vessel coronary artery disease, reversibility of related left ventricular (LV) wall motion abnormalities after successful percutaneous transluminal coronary angioplasty (PTCA) can be predicted by the immediate effect of calcium antagonist nicardipine. Dynamic quantitative left cineventriculography performed four times successively (as the control, 30 minutes after oral nicardipine, 10 minutes after PTCA, and 6 months after PTCA) and hemiaxis method (mean relative hemiaxis shortening or Xdeltar%) were used for wall motion analysis of 48 poststenotic LV myocardial segments divided into three groups: hypokinetic noninfarcted (PNHS, n = 25), infarcted (PIS, n = 12), and normokinetic noninfarcted (PNNS, n = 11) and of 24 normal LV myocardial segments (NS). In PNHS and PIS close correlation (r = 0.75, P < 0.0001 and r = 0.71, P < 0.005) was demonstrated between postnicardipine improvement (21 +/- 4% to 37 +/- 9%, P < 0.0001, and 16 +/- 7% to 20 +/- 8%, P < 0.0005) and 6 months after PTCA improvement (21 +/- 4% to 33 +/- 7%, P < 0.0001, and 16 +/- 7% to 19 +/- 9%, P < 0.0005) of wall motion. It was loose in PNNS and absent in all three groups immediately after PTCA. The sensitivity of the nicardipine test for 6 months after PTCA reversible LV segmental hypokinesia was high in PNHS (95%) and lower in PIS and PNNS (67% and 60%, respectively). The specificity was 100% in PIS, lower in PNNS (67%), and absent in PNHS (owing to lack of true nonresponders). Immediately after PTCA, contraction significantly improved only in PNHS; the nicardipine test was 100% sensitive but nonspecific. Significant improvement of contraction of all groups of poststenotic LV wall segments is expected 6 months after successful PTCA of related artery stenosis, being well predictable by the pre-PTCA effect of nicardipine, at least in PNHS and in PIS. Immediately after PTCA, only in PNHS can significant improvement of contraction be expected.

Effects and interaction of nicardipine and volatile anesthetics in the rat heart-lung preparation

The effects of the calcium channel blocker nicardipine (N) and the volatile anesthetics halothane (H), enflurane (E), isoflurane (I), and sevoflurane (S) on myocardial metabolism after postischemic reperfusion were assessed in the isolated rat heart-lung preparation. Wistar-ST rats were randomly divided into six groups (each groupn=9) as follows: control (C) group, no drugs; N group, N (100 ng·ml^-1); H group, 1% H and N; E group, 2.2% E and N; I group, 1.5% I and N; and the S group, 3.3% S and N. In the presence of the volatile anesthetics, the preparations were perfused for 10 min, made globally ischemic for 8 min, and then reperfused for 10 min. N 100 ng·ml^-1 was administered 5 min before ischemia except in the C group. Three hearts in the C and H groups (eachn=9) and one heart in the E group (n=9) failed to recover from ischemia. The recovery times in the N, I and S groups were significantly shorter than controls. Although there was no significant difference in myocardial lactate concentrations among the groups, ATP content in the N, H, E, I and S groups was significantly higher than in controls. Glycogen content in the N, E, I and S groups was also significantly higher than in controls. These results suggest that N improves myocardial recovery from ischemia; however, in the presence of H or E it may cause significant myocardial depression.

Intravenous nicardipine in hypertensive children

Fourteen hypertensive patients hospitalized in a paediatric intensive care unit were studied to evaluate safety and hypotensive efficacy of intravenous nicardipine. Systolic and diastolic blood pressure significantly decreased 1 h after the beginning of the treatment (1 microgram/kg per minute). Mean decrease in systolic blood pressure during the first 24 h was between 9.9% and 13.4% of the initial value. Mean lowering of diastolic blood pressure was between 16.7% and 25.6%. Nicardipine did not significantly affect heart rate with dose of 1 microgram/kg per minute. No clinical side-effects were observed. Nicardipine could be a first line drug for the treatment of hypertension in paediatric intensive care units.

Hemodynamic tolerability and anti-ischemic efficacy of high dose intravenous diltiazem in patients with normal versus impaired ventricular function

OBJECTIVES

This study was designed to compare the acute systemic and coronary hemodynamic effects of high doses of intravenous diltiazem in patients with normal versus impaired left ventricular function, investigate the safety of this drug and compare its anti-ischemic potential in these two patient groups during pacing-induced stress.

BACKGROUND

Because coronary hemodynamic effects and negative inotropic properties of diltiazem are dose related, high dose intravenous diltiazem may improve anti-ischemic efficacy but may not be tolerated in patients with impaired cardiac function.

METHODS

High dose intravenous diltiazem, 0.4 mg/kg for 5 min followed by 0.4 mg/kg for 10 min, was administered to 23 normotensive patients with coronary artery disease, 11 (group A) with normal and 12 (group B) with impaired ventricular function (ejection fraction < 45%) during two identical arterial pacing stress tests performed 30 min before (pacing test I) and immediately after diltiazem (pacing test II).

RESULTS

Diltiazem was well tolerated despite high peak plasma levels, 869 +/- 152 micrograms/liter (group A) and 926 +/- 169 micrograms/liter (group B). It resulted in immediate but similar reductions in systemic resistance from 1,321 +/- 136 (control value) to 963 +/- 113 dynes.s.cm-5 (group A) and from 1,267 +/- 106 to 865 +/- 58 dynes.s.cm-5 (group B) and in mean arterial pressure from 107 +/- 3 to 93 +/- 4 mm Hg (group A) and from 103 +/- 4 to 86 +/- 4 mm Hg (group B), at 5 min after diltiazem (all p < 0.05 vs. control value). Diltiazem improved stroke output from 36 +/- 3 (control value) to 46 +/- 4 ml/beat per m2 in group B and from 44 +/- 4 (control value) to 49 +/- 5 ml/beat per m2 in group A, an effect that was significantly greater and more prolonged in group B than in group A. Although neither heart rate nor contractility was affected in either group, left ventricular end-diastolic pressure increased in group A (9 +/- 2 mm Hg to 12 +/- 1 mm Hg, p < 0.05) but not in group B. Despite similar reductions in coronary resistance and improvements in coronary flow, diltiazem consistently reduced myocardial oxygen extraction, but only in group B. Also, the anti-ischemic effects of diltiazem were more pronounced in group B. During pacing test II, myocardial lactate extraction normalized in group B (7 +/- 5% vs. -6 +/- 12% [pacing test I]) but not in group A, contractility indexes improved more and the increase in left ventricular filling pressure was reduced to a greater extent in group B. Moreover, the ischemia-induced increase in arterial pressures, observed in both groups during pacing test I, was prevented in group B but recurred in group A during pacing test II.

CONCLUSIONS

High dose intravenous diltiazem is well tolerated, augments coronary flow and improves left ventricular pump function, particularly in patients with preexisting ventricular dysfunction. As its anti-ischemic effects also appear more pronounced in the latter group, high dose diltiazem may be particularly useful when ventricular function is depressed, for example, during prolonged ischemia at rest.

A comparative study of nicardipine and pindolol as second-line treatments in essential hypertension

A controlled, randomized, single-blind, parallel-group study compared the effects of nicardipine hydrochloride/hydrochlorothiazide (HCTZ) with those of pindolol/HCTZ in treatment of essential hypertension. The study included 43 patients aged 30-64 years with supine diastolic blood pressures between 95 and 125 mmHg at baseline. Patients initially received 50 mg/day HCTZ for 6 weeks and those patients whose diastolic blood pressure remained at or above 90 mmHg at week 6 (n = 29) completed a 6-week comparative phase in which they were given, in addition, either 30 mg nicardipine hydrochloride or 5 mg pindolol three times daily. Nicardipine was more effective than pindolol as a second-line treatment in controlling blood pressure but, because patients who were treated with nicardipine/HCTZ had higher baseline blood pressures, significance was lost when results were adjusted for the baseline blood pressure values. Treatment was described as 'very good' by 71.4% of patients in the nicardipine/HCTZ group and by 53.9% of those in the pindolol/HCTZ group; thus, both second-line antihypertensives were well accepted. Although 45% of patients in of each treatment group reported treatment-related adverse events, none experienced postural hypotension and no adverse event was unexpected.

Systemic vasomotor interaction between nicardipine and hypocapnic alkalosis in man

The effects of hypocapnic alkalosis on the vasodilating action of nicardipine were studied in 6 patients after cerebral arterial aneurysm surgery. Each patient served as his/her own control during the 6 steps of the study. T0: baseline; T1: hypocapnic alkalosis alone (PaCO2: 3.5 kPa); T2: hypocapnic alkalosis and bolus injection of nicardipine (30 micrograms.kg-1 i.v.); T3: hypocapnic alkalosis and continuous 60 min infusion of nicardipine (0.5 microgram.kg-1.min-1), T4: determination of the infusion rate required to neutralize the effect of hypocapnic alkalosis; T5: same continuous dose of nicardipine as in T4 but reversal of hypocapnic alkalosis. Hypocapnic alkalosis alone caused a significant increase in the systemic vascular resistance index by 20% (T1). The bolus injection of nicardipine reversed this first effect (T2). The continuous infusion of nicardipine in T3 was insufficient to cancel the haemodynamic effect of hypocapnic alkalosis. During T4 the plasma levels required to neutralize completely the effect of hypocapnic alkalosis were twice those at T3. Normalization of the PaCO2 in step T5 induced a significant fall in the systemic vascular resistance index by 27.5% as compared with T0. In this study hypocapnic alkalosis modified the relationship between plasma levels of nicardipine and its expected vasoactive effects. This interaction was reversible.

Double-blind, randomized comparative study of the antihypertensive effect of nicardipine slow-release and nifedipine slow-release in hypertensive patients with coronary heart disease

The main aim of this study was to investigate whether a new slow-release formation of nicardipine can control hypertension and whether its antihypertensive effect is manifest throughout the dose intervals. In a randomized, double-blind placebo-controlled study, the antihypertensive effect of two calcium antagonists (Type II) was investigated in two independent groups of hypertensive patients with coronary artery disease. One group of patients received 40 mg nicardipine slow-release b.i.d. and the other 20 mg nifedipine slow-release b.i.d. The effect of the active drugs on blood pressure (BP), heart rate, and hemodynamics was compared with placebo within each group. In addition, a group comparison was made to establish whether nicardipine had any advantage over nifedipine. Twenty-eight patients [27 female, 1 male; 55 (41-72) years old], 18 with previous myocardial infarction (MI) entered the study (nicardipine, 15 patients; nifedipine, 13 patients). A placebo period of 3 days was followed by a 13-day drug treatment period. From the first to last trial day, BP and heart rate were measured three times daily. At the end of the placebo and the active drug periods, the following measurements were carried out: ambulatory BP monitoring by half-hourly recording for 12.5 hours with the Remler system, ergometric tests with ECG, and right heart catheterization. Both drugs lowered the BP at rest, during exercise, and during usual daily activities. The antihypertensive effect of nicardipine was significant for the daytime mean arterial BP (MAP) and for systolic BP and diastolic BP at various stages of the exercise tests. The difference between the effect of nicardipine and nifedipine was not significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of nicardipine on somatosensory evoked potentials in patients with acute cerebral infarction

We evaluated the effect of nicardipine, a calcium channel blocker, on somatosensory evoked potentials (SEP) in 26 patients with acute cerebral infarction. Post treatment, 58% (15/26) of the N20 and P25 latencies were prolonged in the affected hemispheres; 8% (2/26) were shortened; and 35% (9/26) did not change. The mean N20 and P25 latencies were significantly prolonged two hours post treatment in the affected hemisphere (N20, P less than 0.01, P25 P less than 0.01). Nicardipine (Ni) had no effect on SEP components in the intact hemispheres. Seventy five per cent of the 12 patients with hypertension had a decrease in blood pressure (BP) after taking nicardipine, but there were no undesirable side effects or worsening of neurological signs. Our study demonstrates that nicardipine prolongs the latencies of short-latency components of SEP in the affected hemisphere after acute ischaemic stroke and also decreases BP. These observations suggest that nicardipine therapy might impair neuronal function in the ischaemic zone.

The cardiovascular effects of oral nifedipine and nicardipine: a double-blind comparison in healthy volunteers using transthoracic bioimpedance cardiography

The cardiovascular effects of single oral doses of nifedipine (5 and 10 mg) and nicardipine (20 and 30 mg) were compared in a placebo controlled double-blind crossover study involving 8 healthy male volunteers. Two hours following drug administration stroke volume and cardiac index were measured non-invasively using transthoracic electrical bioimpedance cardiography during passive tilting, graded bicycle exercise, and recovery from exercise. Two separate experiments were performed in the absence of active drug to allow the reproducibility of the measurements to be assessed. Coefficients of variation (within experiment/between experiments) for cardiac index were 7.0%/19.9% at rest and 11.5%/9.3% at 180 W exercise. Both nifedipine and nicardipine increased stroke volume and cardiac index and reduced total peripheral resistance (mean blood pressure/cardiac index) at all times in the experiment. Reductions in peripheral resistance were similar for nifedipine 10 mg and nicardipine 20 mg but in these doses slightly larger increases in heart rate were produced by nifedipine, and in stroke volume and cardiac index with nicardipine. The study shows that the cardiovascular effects of nifedipine and nicardipine can be detected using impedance cardiography which is a simple, safe, and inexpensive technique. The differences between the effects of the two drugs were small. Although some were of statistical significance and are consistent with a less marked cardiodepressant effect for nicardipine, the clinical importance of these observations is uncertain. Further studies to examine the effect of oral nifedipine and nicardipine in patients with impaired ventricular function may be helpful in clarifying this tissue.

Intravenous nicardipine for treatment of intraoperative hypertension during abdominal surgery

Twenty patients, American Society of Anesthesiologists class I or II, who developed intraoperative hypertension (mean arterial pressure greater than 110 mm Hg) during abdominal surgery under balanced general anesthesia were randomly assigned to two groups. The nicardipine group (n = 10) received 5 mg of nicardipine hydrochloride, and the placebo group (n = 10) received 5 mL of nicardipine solvent injected intravenously over a 5-minute period in a blind manner. Arterial pressure was recorded for 15 minutes after the injection was started. If the mean arterial pressure did not decrease at least 10% at 15 minutes, the trial was opened and patients received 5 mg of nicardipine. None of the patients in the nicardipine group received nicardipine in an open manner, in contrast with 7 of the 10 patients in the placebo group (P less than 0.03, Fisher exact test). During both the blind period and the open trial, nicardipine induced a 34% decrease in systolic, diastolic, and mean arterial pressure. Minimal values of pressure were noted at 6 minutes; however, arterial pressure remained below the pre-nicardipine injection values and near preoperative values for 45 minutes. No severe hypotension was observed, but the nicardipine injection was stopped at 3 mg in two cases during the blind period because of the rate of pressure reduction. Heart rate remained unchanged during the decrease in arterial pressure in both groups. This study indicates that nicardipine is an effective, long lasting, and safe therapy for intraoperative hypertension during abdominal surgery.

Usefulness of nicardipine as monotherapy for chronic, stable angina

Using a double-blind, Latin square protocol designed to detect dose response, nicardipine hydrochloride, a new calcium antagonist, was studied as monotherapy for stable exertional angina. Eighty-one patients were enrolled in the trial and 62 patients were included in greater than or equal to 1 primary efficacy analyses. Patients received 1 to 2 weeks of placebo run-in, then 5 weeks of treatment with placebo and with 10, 20 and 30 mg of nicardipine given 3 times daily. Patients completed symptom diaries, were monitored with 24-hour electrocardiographic Holter monitors and underwent serial exercise treadmill tests. By 1 hour, 10, 20 and 30 mg of nicardipine administered 3 times daily produced statistically significant, dose-related improvements in all key exercise parameters, which persisted at the 4-hour evaluation. The systolic blood pressure at rest and during exercise decreased, but the pulse slightly increased. The peak rate-pressure product was unchanged. The side effects were not severe. Nicardipine hydrochloride is an effective, well-tolerated medication for the treatment of stable exertional angina, and is a good alternative to currently available calcium antagonists.

Nicardipine HCl: clinical experience in patients undergoing anaesthesia for intracranial aneurysm clipping

Previous studies have reported haemodynamic interactions between dihydropyridine calcium antagonists and general anaesthesia. During anaesthesia for intracranial aneurysm surgery, we prospectively compared haemodynamic values obtained from 13 patients being treated with nicardipine HCl (0.15 mg.kg-1.hr-1 IV) for cerebral vasospasm against values obtained from 11 untreated controls. Prior to induction of anaesthesia, nicardipine-treated patients had significantly elevated mean +/- SD cardiac index (5.67 +/- 1.30 vs 3.99 +/- 0.73 L.min-1.m-2) while MAP (86 +/- 10 vs 99 +/- 14 mmHg) and systemic vascular resistance (647 +/- 227 vs 1141 +/- 404 dynes.sec-1.cm-5) were reduced. Heart rate, CVP, and PACWP were similar between groups. Anaesthesia induction and tracheal intubation resulted in similar haemodynamic values between groups with the exception of CVP (10 +/- 5 vs 5 +/- 2 mmHg) and PACWP (15 +/- 5 vs 8 +/- 3 mmHg) which were elevated in the nicardipine group (P less than 0.01). Mannitol infusion and deliberate hypotension resulted in nearly identical haemodynamic responses in both groups. Nicardipine-treated patients required more intravenous fluids during the operative procedure (2.4 +/- 0.3 L vs 1.5 +/- 0.4 L, P less than 0.05) and were less likely to require isoflurane supplementation to morphine sulphate/nitrous oxide anaesthesia (P less than 0.01). In summary, our experience with nicardipine HCl revealed no major untoward effects with respect to maintenance of intraoperative haemodynamic stability despite continuous antivasospasm therapy with this vasodilator.

Electrophysiologic evaluation of intravenous nicardipine in man

The acute electrophysiological effects of intravenous nicardipine (0.014 mg/kg per min for 5 minutes) were studied in 12 subjects with estimated normal sinus node functions and atrioventricular conduction parameters. The most important effects were sinus cycle length shortening, increase of corrected sinus node recovery time and reduction of effective and functional refractory period of the atrioventricular node. Sinuatrial conduction time, atrial refractory periods, intranodal conduction, bundle branch refractoriness and ventricular refractoriness were unchanged. Systolic and diastolic blood pressure was reduced. The clinical implications of these properties of the drug are discussed and compared with those of verapamil, diltiazem and nifedipine.

Nicardipine in elderly patients with hypertension: a review of experience in France

A double-blind, placebo-controlled clinical trial in France has studied the efficacy and safety of nicardipine in 31 elderly patients, aged 57 to 95 years (mean age 84 years), 16 of whom were actively treated with nicardipine, 10 to 30 mg three times a day (mean dose 69.4 mg/day). After 4 weeks, nicardipine lowered mean blood pressure (186/99 to 150/83 mm Hg; p less than 0.001), and the changes in systolic and diastolic blood pressure were significantly greater in the nicardipine group than in the placebo group. Nicardipine was well tolerated; orthostatic hypotension was not observed and there was no change in heart rate. Plasma renin activity (PRA) was measured in eight patients, but there was no correlation between PRA and the antihypertensive effect of nicardipine. Results of a pharmacokinetic study performed in 15 elderly patients showed a rapid rate of absorption and higher plasma levels than those observed in younger patients with hypertension (mean age 54 years). The results support those of the major French multicenter open study of 29, 104 elderly patients with hypertension (mean age 64 +/- 12 years) treated with nicardipine. The findings of this trial are reviewed and discussed, and recommendations made on the directions for future research in cardiovascular medicine with calcium channel blockers. Results of the trials discussed in this article show that nicardipine is an effective and well-tolerated drug in elderly patients and has wide-ranging effects on the cardiovascular system.

Effects of nicardipine on chronic stable effort angina: a non-invasive assessment

The effects of 60 mg/day nicardipine hydrochloride were evaluated in a 4-week single-blind study on 12 patients with chronic stable effort angina. All patients completed the treatment with few reports of adverse effects. Nicardipine hydrochloride was effective in reducing the incidence of anginal attacks and consumption of glyceryl trinitrate. Treadmill exercise time, angina onset time and the time to 1 mm ST-segment depression were increased. The extent of ST-segment depression was reduced at maximum comparable exercise, with a reduced rate-pressure product and, at maximum exercise, with an increased rate-pressure product. Myocardial stress 201Tl scintillography was carried out in eight of the patients and showed improved washout in antero-septal, infero-apical and postero-lateral segments. Echocardiographic measures of left ventricular function were enhanced because of reduction of afterload. Systemic vascular resistance and end-systolic stress were also decreased and a significant correlation was found between the increase in ejection fraction and reduction of systolic blood pressure. It is concluded that nicardipine hydrochloride is effective in the control of stable effort angina by reducing myocardial oxygen consumption and enhancing coronary blood flow thereby improving left ventricular function.

Cardiovascular interaction between sevoflurane and nicardipine in open chest dogs

Cardiovascular interaction between nicardipine and sevoflurane was examined in dogs and compared with nicardipine-thiopental interaction and nicardipine-halothane interaction. The bolus intravenous injection of nicardipine at dosages of 15 micro g/kg and 30 micro g/kg under sevoflurane anesthesia produced transient decreases in blood pressure, systemic vascular resistance, left ventricular pressure, left ventricular (dp)/(dt) and -(dp)/(dt), and a slight increase in cardiac output. The degrees of these changes were almost identical to those under thiopental or halothane anesthesia. Left and right atrial pressure, pulmonary arterial pressure, pulmonary vascular resistance were not changed by nicardipine under any of the three anesthetics. These results suggest that the cardiovascular interaction of nicardipine and sevoflurane is additive and similar to that of nicardipine and halothane and that the cardiovascular changes induced by nicardipine are not modified by the presence of anesthetics.

Efficacy and mechanism of action of a calcium channel blocker after global cerebral ischemia in rats

Dihydropyridine calcium channel blockers such as nicardipine are under evaluation for treating acute cerebral ischemia because they may increase cerebral blood flow by causing vasodilation and because they may be cytoprotective in part by limiting production of arachidonic acid metabolites. We demonstrated in a previous study that nicardipine improves postischemic neuronal function, as measured by somatosensory evoked potentials, without reducing the extent of light-microscopic CA-1 hippocampal histologic damage. To characterize further the effect of nicardipine on global ischemic injury, we administered the drug beginning 24 hours before 30 minutes of four-vessel ischemia in Wistar rats. We then measured hippocampal ATP, phosphocreatine, and glucose contents immediately and 2 hours after ischemia, and measured learning ability (working and reference errors) on an eight-arm radial maze beginning 30 days after ischemia. To gain insight into the possible mechanism of action, we measured production of arachidonic acid metabolites (eicosanoids: TXB2 and 6-keto-PGF1 alpha) and hemispheric and hippocampal cerebral blood flow by the [14C]butanol indicator fractionation technique immediately and 2 hours after ischemia. Nicardipine was associated with fewer working errors (p less than 0.02) but no difference in reference errors. The drug had no effect on energy metabolites, cerebral blood flow, or eicosanoids immediately after ischemia, but ATP, phosphocreatine, and cerebral blood flow all returned to normal levels significantly more rapidly during reperfusion in treated rats. Nicardipine improves behavioral, electrophysiologic, and mitochondrial function after ischemia without preventing cellular damage and improves postischemic reperfusion. The drug's positive effect appears to occur during reperfusion.

Calcium channel blockers in systemic hypertension

Alterations in transmembrane flux of calcium ions may be playing a role in the pathophysiology of systemic hypertension. Calcium channel blockers have been shown to be effective antihypertensive drugs with excellent safety profiles. They are efficacious in the long term treatment of systemic hypertension in all population subgroups, and have special applicability for treating patients with hypertensive urgencies and individuals with concomitant diseases such as angina pectoris and arrhythmias.

Acute inotropic effects of intravenous nifedipine and its vehicle compared with saline: a double-blind study of systolic time intervals in normal subjects

1. The inotropic effects of intravenous nifedipine and its vehicle were studied noninvasively in a double-blind placebo controlled crossover fashion using systolic time intervals in 12 normal subjects. 2. Nifedipine caused vasodilation, a fall in systolic and diastolic blood pressure, and increased heart rate. The vehicle alone caused vasodilation and decreased systolic blood pressure, without a change in heart rate. 3. Nifedipine increased left ventricular ejection time (LVET) and decreased pre-ejection period (PEP) and the ratio PEP/LVET, whereas the vehicle alone had the opposite effect. Neither treatment affected the total duration of electromechanical systole. 4. These results suggest that the vehicle has a negative inotropic effect, which is overcome by the indirect positive inotropic effect of nifedipine when they are administered together systemically.

A randomized double-blind crossover study of nicardipine and nifedipine in patients with angina pectoris and concomitant essential hypertension

The two dihydropyridine calcium antagonists, nicardipine and nifedipine, were compared in 12 patients with both stable angina pectoris and systemic hypertension using a double-blind, crossover protocol. After a 2-week placebo run-in period, each patient was randomized to either nicardipine or nifedipine; each drug was titrated up to either blood pressure normalization, appearance of adverse effects, or maximal dosage (40 mg, three times a day with nicardipine and 30 mg, three times a day with nifedipine) and then administered for 4 weeks. Maximal symptom-limited exercise tests were performed at the end of the placebo run-in and each treatment period, 3 and 8 hours after drug administration. Nicardipine and nifedipine were used at the mean doses of 100 +/- 20 mg/day and 57 +/- 20 mg/day, respectively. Both drugs reduced, significantly and similarly, standing and supine blood pressure, frequency of anginal episodes, and nitroglycerin consumption. At 3 hours after drug administration, exercise duration and time to 1-mm ST depression increased significantly from 402 +/- 84 and 306 +/- 108 seconds, respectively, with placebo; to 533 +/- 135 and 442 +/- 138 seconds during nicardipine; and to 518 +/- 118 and 437 +/- 133 seconds during nifedipine, with a concomitant reduction of peak ST depression. Both submaximal and maximal exercise diastolic blood pressure were significantly reduced by the two calcium antagonists whereas systolic blood pressure was decreased only at submaximal but not at maximal exercise; the heart rate was not significantly modified by the two drugs at any exercise stage.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics and pharmacodynamics of nifedipine infusion in normal volunteers

Two studies of the pharmacokinetics and pharmacodynamics of intravenous nifedipine infusion were performed: the first, a randomised double-blind crossover study of nifedipine and its vehicle in eight subjects, the second a dose ranging study in nine subjects. Nifedipine pharmacokinetics did not vary with dose or duration of infusion up to 8 h, and are similar to those reported for other nifedipine preparations. Nifedipine increased heart rate and forearm blood flow and decreased blood pressure after bolus injection but not during prolonged infusion. The vehicle decreased blood pressure and increased forearm blood flow after bolus injection but not during prolonged infusion. It did not affect heart rate. The vehicle's haemodynamic activity has not been previously recognised and is of potential importance in the study of this and similar preparations of calcium antagonists.

Nicardipine. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy, in the treatment of angina pectoris, hypertension and related cardiovascular disorders

Nicardipine is an antagonist of calcium influx through the slow channel of the cell membrane and has been shown to be an effective and relatively well-tolerated treatment for stable effort angina and rest angina due to coronary artery spasm, and mild to moderate hypertension. Although its exact mechanism of action in these disease states has not been precisely defined, the potent coronary and peripheral arterial dilator properties of nicardipine, with concomitant improvements in oxygen supply/demand and reductions in systemic vascular resistance, are of major importance. Clinical studies have shown that nicardipine appears to be effective in the treatment of chronic stable exercise-induced angina pectoris and possibly in angina at rest due to coronary artery spasm. In the treatment of stable angina, nicardipine has proved to be equally as effective as nifedipine. However, haemodynamic and clinical studies indicate that nicardipine may have a further advantage of not depressing cardiac conduction or left ventricular function, even in patients with compromised cardiac pumping ability. Nicardipine also appears to be useful as initial monotherapy or in combination with other antihypertensive drugs when used in the treatment of mild to moderate hypertension, and may have some advantages over other vasodilators in this regard in that it may not be as frequently associated with fluid retention or weight gain as other similar drugs. In the treatment of hypertension nicardipine has been shown to be as effective as drugs such as hydrochlorothiazide, cyclopenthiazide, propranolol and verapamil in short term studies although confirmation of its long term usefulness in well-designed clinical trials is still required. Similarly, although the use of nicardipine in other disorders such as congestive heart failure and cerebrovascular disease has provided encouraging preliminary results, more studies are needed to clarify its place in their treatment. Side effects appear to be dose related and more frequent within the first few weeks of therapy. Most of these effects are minor and transient in nature and include headache, flushing and peripheral oedema. Thus, there is no doubt that nicardipine provides a suitable alternative to other drugs available for the treatment of angina and hypertension. However, further well-designed comparative clinical trials are needed to clarify its relative place in the long term management of these disorders.

Nicardipine in the treatment of essential hypertension controlled 6-month-study comparing nicardipine with propranolol at rest and during exercise

Thirty patients with mild to moderate essential hypertension entered a randomised double-blind parallel group study for 6 months to compare the effects of the new calcium channel blocker nicardipine 90 mg/day and propranolol 240 mg/day. Both drugs reduced systolic and diastolic blood pressures significantly in the supine and in standing positions. After 6 months of treatment, nicardipine had reduced the supine systolic and diastolic blood pressures by 16 and 17 mm Hg, respectively, and propranolol by 15 and 12 mm Hg. While propranolol treatment led to a marked decline in heart rate, nicardipine caused a small but statistically significant increase in heart rate throughout the study. Both drugs reduced blood pressure during maximal exercise, but propranolol had a greater effect. During exercise nicardipine did not affect the heart rate, whereas propranolol dramatically reduced it. Nicardipine did not produce any ECG changes at rest or during exercise. The side-effects for nicardipine were mild and were related to the vasodilatation induced by the drug. No abnormalities in routine blood chemical tests were found for either of the drugs. Nicardipine appears to be an effective single drug treatment for mild to moderate hypertension.

Effects of intravenous administration of a calcium antagonist on prostaglandins and thromboxane in plasma and urine in humans

The effects of a calcium antagonist [Nicardipine hydrochloride (NH)] on the prostaglandin [prostaglandin E2 (PGE2), and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha)] and thromboxane B2 levels in the blood and urine were examined in 6 patients with essential hypertension following intravenous infusion of NH for 120 minutes. At the same time, the plasma renin activity (PRA), plasma aldosterone concentration (PAC), and plasma and urinary electrolyte levels were also determined. During NH administration, the blood pressure was significantly decreased (p less than 0.05) with an increased pulse rate (p less than 0.05). PRA was significantly increased after NH loading (p less than 0.05) but PAC showed no change. The plasma PGE2 and 6-keto-PGF1 alpha levels tended to increase slightly, while the blood thromboxane B2 level showed a decreasing tendency. The 6-keto-PGF1 alpha to thromboxane B2 ratio was significantly increased after NH loading as compared to the preloading ratio (p less than 0.05), and then returned to the preloading value at about 30 minutes after discontinuation of NH loading. The urinary excretions of PGE2, 6-keto-PGF1 alpha and thromboxane B2, PGE2 and 6-keto-PGF1 alpha tended to decrease after NH loading. In particular, the decrease in PGE2 was statistically significant (p less than 0.05). No change occurred in the urinary excretion of thromboxane B2. The above findings indicate that NH increased the plasma 6-keto-PGF1 alpha to thromboxane B2 ratio but decreased the urinary excretion of prostaglandins. In addition, the possible involvement of an enhanced 6-keto-PGF1 alpha/thromboxane B2 ratio in part of the hypotensive mechanism of NH is suggested.

Renal effects of nicardipine in patients with mild-to-moderate essential hypertension

We studied the renal effects of nicardipine, a calcium entry blocker, in seven patients with mild-to-moderate essential hypertension. Glomerular filtration rate (GFR) and renal blood flow (RBF) were measured by means of thiosulfate and para-aminohippurate, respectively. Intravenous administration of nicardipine hydrochloride (0.5 mg) increased RBF by 26.8 +/- 5.8% (mean +/- SEM, p less than 0.01), GFR by 35.4 +/- 12.4% (p less than 0.05), and urinary excretion of sodium by 56.4 +/- 10.7% (p less than 0.05) with a significant (p less than 0.01) reduction in systolic and diastolic blood pressure as compared to control values. Nicardipine decreased total renal vascular resistance by 30.0 +/- 3.2% (p less than 0.05) from the control value, while filtration fraction remained unchanged. Our results indicate that nicardipine has several favorable renal effects with a concomitant hypotensive action in patients with mild-to-moderate essential hypertension.

Effects of nicardipine on left ventricular function and energetics in man

The effects of nicardipine, a new dihydropyridine calcium antagonist, on left ventricular function and energetics were studied in 13 patients. Nicardipine was administered as a 2 mg bolus (i.v.) followed by an infusion titrated to maintain a 10-20 mm Hg decrease in systolic pressure. Nicardipine increased heart rate 19% (P less than 0.001) while left ventricular end-diastolic pressure was not significantly changed and stroke volume (ml) increased 13% (P less than 0.01). Peak values for the first and second time derivatives of left ventricular pressure were increased by 26% (P less than 0.01) and 50% (P less than 0.02) respectively. Peak aortic blood flow, peak aortic blood acceleration, and the peak rate of change of ejection power were increased 86% (P less than 0.001), 123% (P less than 0.01), and 113% (P less than 0.001), respectively. Stroke work was not changed during nicardipine infusion. External power increased by 40% (P less than 0.01); however, the ratio of oscillatory to total power was not significantly different. Although the product of heart rate and systolic aortic pressure was not significantly altered with nicardipine, myocardial oxygen consumption increased 18% (P less than 0.02) with a disproportionate increase in coronary blood flow of 41% (P less than 0.001) and decrease in coronary resistance of 39% (P less than 0.001). The time constant for left ventricular isovolumic relaxation decreased 22% (P less than 0.001) during nicardipine infusion while the minimum value of dP/dt was unchanged. Thus, when administered intravenously in man, nicardipine is a potent coronary and systemic vasodilator producing reflex tachycardia, increased indices of myocardial contractile state, and improved isovolumic relaxation with an associated increase in myocardial oxygen consumption.

Pharmacokinetic, haemodynamic and radionuclide studies with nicardipine in coronary artery disease

Pharmacokinetic, haemodynamic and radionuclide studies explored the acute pharmacokinetic and pharmacodynamic actions of nicardipine in patients with coronary heart disease. Nicardipine infusion resulted in dose-related reductions in systolic and diastolic blood pressure and an increased heart rate. Pharmacodynamic activity was evident between 12 and 24 min following 5 and 10 mg i.v. nicardipine but by 3-6 min following the higher doses of 15 and 20 mg; hypotensive activity persisted for up to 2 h. Post-infusion nicardipine concentrations declined biexponentially; however the limited data precluded formal compartmental analysis. Plasma clearance ranged from 5-12 ml/min/kg, and appeared lower than previously reported volunteer data. The haemodynamic actions of nicardipine (10 mg infusion over 10 min) in 6 patients undergoing diagnostic catheterization were reductions in systolic, diastolic and mean systemic arterial pressure and systemic vascular resistance index. Heart rate and stroke volume index increased, and there was a small but statistically significant increase in pulmonary artery occluded pressure. Radionuclide parameters were measured in 20 patients with stable angina, at rest and during supine bicycle exercise, before and 3-5 min after nicardipine 10 mg intravenously. The left ventricular ejection fraction increased by 4% at rest but not during exercise. The left ventricular rest and exercise ejection and filling rates both increased with a concurrently reduced left ventricular ejection time. There was a highly significant inverse relationship between baseline exercise ejection fraction and the response to nicardipine; ejection fraction increased with low initial values but was either unchanged or fell with higher initial values.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of nicardipine and propranolol for chronic stable angina pectoris

In a double-blind, randomized, crossover clinical trial, a new calcium antagonist, nicardipine (90 mg/day in 3 divided doses), was compared with propranolol (120 mg/day in 3 divided doses) in 25 patients with chronic stable angina. The mean weekly frequency of angina episodes decreased from 7.8 +/- 1.2 (+/- standard error of the mean) with placebo to 3.8 +/- 1.2 with nicardipine treatment and 3.5 +/- 1 with propranolol treatment (p less than 0.001). With exercise testing, 5 patients receiving nicardipine and 3 receiving propranolol had no angina or ST-segment changes. Comparing paired samples of both drugs with placebo, significant improvement occurred in exercise duration (nicardipine, 1.3 +/- 0.3 minutes, p less than 0.001; propranolol, 1.0 +/- 0.4 minutes, p less than 0.01), time to onset of angina (nicardipine, 1.5 +/- 0.4 minutes, p less than 0.001; propranolol, 1.5 +/- 0.5 minutes, p less than 0.001), maximal ST-segment changes (nicardipine, 0.7 +/- 0.1 mm, p less than 0.01; propranolol, 0.06 +/- 0.1 mm, p less than 0.01) and time to 1 mm of ST depression (nicardipine, 2.5 +/- 0.4 minutes, p less than 0.01; propranolol, 2.0 +/- 0.3 minutes, p less than 0.01). One patient receiving propranolol and 2 receiving nicardipine withdrew from the study because of transient side effects. Mild side effects occurred in 10 patients receiving propranolol and 5 receiving nicardipine. Nicardipine proved to be safe and effective for patients with chronic stable angina; it had fewer side effects than propranolol in the doses used.

Nicardipine for angina pectoris at rest and coronary arterial spasm

The antiischemic effects and safety of nicardipine were assessed in 17 patients with angina at rest and coronary arterial spasm in a randomized placebo-controlled study over 8 to 13 weeks. Eleven patients had previously had unsatisfactory results with long-acting nitrates or other calcium blockers. The average daily dosage of nicardipine for optimal angina relief was 89 mg (range 40 to 160). During the double-blind phase, angina frequency decreased with nicardipine compared with placebo (mean 0.47 vs 2.11 attacks/day, p less than 0.05). A similar decrease in nitroglycerin requirements occurred (0.51 vs 2.77 tablets/day, p less than 0.05). During placebo periods, 51 episodes of ischemic ST-segment shifts occurred during 482 hours of ambulatory electrocardiographic monitoring and 12 (24%) were associated with angina. During nicardipine treatment, only 15 episodes of ST-segment shifts occurred during 498 hours of monitoring. In 1 patient a burning skin rash developed; otherwise, the drug was generally well tolerated. Thus, nicardipine is effective and safe in preventing symptomatic and asymptomatic ischemia in patients with coronary spasm. It may be particularly beneficial in patients with unsatisfactory responses to other therapy.

Coronary and systemic hemodynamic effects of nicardipine

Systemic and coronary hemodynamic effects of a new dihydropyridine calcium antagonist, nicardipine, were studied in 15 patients. Nicardipine was administered as a 2-mg bolus intravenously followed by an infusion titrated to maintain a 10 to 20-mm Hg decrease in systolic pressure. Nicardipine increased both heart rate from 69 +/- 3 to 81 +/- 3 beats/min and cardiac output from 7.3 +/- 0.5 to 9.9 +/- 0.5 liters/min (both p less than 0.001) as systemic vascular resistance decreased from 1,183 +/- 70 to 733 +/- 33 dynes s cm-5 (p less than 0.001). Left ventricular end-diastolic pressure remained constant, at 14 +/- 1 vs 14 +/- 1 mm Hg as stroke volume increased from 108 +/- 6 to 123 +/- 6 ml/m2 (p less than 0.001). Coronary blood flow increased from 102 +/- 9 to 147 +/- 13 ml/min, while coronary resistance decreased from 1.17 +/- 0.1 to 0.7 +/- 0.1 mm Hg/ml/min (both p less than 0.001). Heart rate-systolic blood pressure product did not change (104 +/- 5 vs 106 +/- 5 beats/min mm Hg X 10(-2), difference not significant) with drug administration. At the same heart rate before and during nicardipine administration (using atrial pacing in 6 patients), significant augmentation of coronary flow was still observed. Thirteen of 14 patients showed a greater percent decrease in coronary resistance than systemic vascular resistance. Nicardipine differs from other calcium antagonists with respect to consistent augmentation of coronary blood flow. This effect appears to be the result, in part, of increased potency in the coronary bed compared with the systemic vascular bed.

Noninvasive assessment of the haemodynamic effects of nicardipine in normotensive subjects

Calcium antagonists reduce myocardial contractility in vitro. Nicardipine is a dihydropyridine derivative with enhanced selectivity for vascular smooth muscle. We have studied the pharmacokinetics and the haemodynamic effects that occur in man following bolus intravenous administration of nicardipine. Ten normotensive male subjects received either nicardipine or placebo i.v., allocated in a randomised double-blind manner, over 60s. Plasma nicardipine concentration, blood pressure, heart rate, and systolic time intervals were measured before dosing and at frequent intervals between 1 and 360 min post dosing. At 160 micrograms kg-1, adequate plasma levels of nicardipine were obtained to permit analysis of individual pharmacokinetic variables, and significant and consistent haemodynamic effects were seen. After injection of nicardipine, systolic BP and the QS2 (measure of total electromechanical systole) and QT intervals were not altered. The changes in BP and heart rate were consistent with arteriolar vasodilatation. The changes in PEP and LVET suggest an increase in cardiac contractility, which is unlikely to be a direct effect of nicardipine on the myocardium but rather a result of afterload reduction. The close correlation of nicardipine plasma level with haemodynamic effect should permit accurate dose titration. The net increase in contractility should allow nicardipine to be administered safely with beta-adrenoceptor blocking drugs.

Nicardipine for stable angina pectoris

Nicardipine, 30 and 40 mg thrice daily, was administered to 66 patients with stable angina pectoris in a multicentre, randomised, double-blind, cross-over trial. With nicardipine therapy, duration of exercise and cumulative oxygen consumption increased, while times to onset of angina and 1 mm ST segment depression were prolonged. Anginal frequency and nitroglycerin consumption declined with use of nicardipine, but this did not reach statistical significance. Resting heart rate increased slightly and resting blood pressure decreased. Two patients on nicardipine and one on placebo sustained acute infarction. Otherwise, side effects were generally mild and transient.

Effect of nicardipine in elderly hypertensive patients

The purpose of this study was to test tolerance and the antihypertensive effect of nicardipine, a new calcium antagonist, in 31 elderly patients aged 57-95 years. The study was conducted as a double-blind trial. The patients were allocated randomly to either active or placebo treatment. Sixteen patients were given 10-30 mg of nicardipine three times a day (mean dose, 69.4 mg per day); 15 other patients received a matching placebo. After 4 weeks, nicardipine lowered mean blood pressure, and the changes in systolic and diastolic blood pressure were significantly greater in the nicardipine group than in the placebo group. Nicardipine was tolerated very well, and orthostatic hypotension was never observed. There was no change in heart rate. Plasma renin activity (PRA) was measured in eight patients. There was no correlation between PRA and the antihypertensive effect of nicardipine. A pharmacokinetic study performed in 15 elderly patients showed a fast rate of absorption and also higher plasma levels than those observed in hypertensive adults (mean age, 54 years). This trial demonstrates the effectiveness of nicardipine in elderly hypertensive patients.

Prevention of vasospastic angina with nicardipine

Anti-ischaemic effects and safety of nicardipine were assessed in 14 patients with vasospastic angina using a placebo comparison, cross-over design study for 8-13 weeks. The average daily dose of nicardipine for optimal angina prevention was 84 mg (range 40-160 mg). Nicardipine administration, as compared with placebo, significantly reduced anginal frequency and nitroglycerin consumption during the single- and double-blind phases of the study. Nicardipine appears to be effective in the prevention of vasospastic angina and not to cause major adverse effects.

The acute haemodynamic effects of oral nicardipine

The haemodynamic effects of oral nicardipine at two different doses were assessed in fifteen patients at rest following diagnostic cardiac catheterisation. Six patients received four doses of 20 mg nicardipine hydrochloride orally every 8 h, and nine patients received four doses of 30 mg orally every 8 h. No side effects were encountered with either dose. At both dose levels, there was a significant fall in systemic vascular resistance, significant increases in heart rate and cardiac output, and no change in stroke volume index. No changes were seen in pulmonary vascular haemodynamics, and there were no significant changes in mean arterial pressure. Plasma levels of nicardipine reached a peak within 1 h. In parallel with the haemodynamic effects, the plasma concentrations achieved after the third and fourth doses were higher than after the first dose. These haemodynamic changes are consistent with a vasodilator effect, which produces a decrease in peripheral vascular resistance. It would appear that the 30 mg dose has a more potent vasodilator action than the 20 mg dose and, in the patients studied, this larger dose was not associated with any side effects.

Comparative efficacy of nicardipine, a new calcium antagonist, versus nifedipine in stable effort angina

The relative efficacy of nicardipine and nifedipine was examined in a double-blind placebo-controlled randomized crossover trial. We studied 12 patients with chronic effort angina involving reproducible angina and greater than or equal to 1.5 mm of ST-segment depression on exercise treadmill test performed before and after a 1-week control period of single-blind placebo administration. Subsequently, indistinguishably prepared nicardipine 20 mg, nifedipine 10 mg, or placebo, four times a day, was administered in a randomized double-blind crossover fashion for 3 weeks (total study period 9 weeks). Exercise treadmill test was performed at the end of each 3-week period. Both nicardipine and nifedipine significantly reduced the frequency of anginal attacks and nitroglycerin consumption. Compared with placebo both drugs caused a comparable increase of the duration of exercise, of the time to angina and to the appearance of 1.5 mm ST-segment depression (P less than 0.05 placebo versus nicardipine; P less than 0.01 placebo versus nifedipine respectively). No significant side effects were observed with either drug. We conclude that nicardipine and nifedipine produce similar hemodynamic and clinical effects in patients with stable effort angina.

Nicardipine: pharmacokinetics and effects on carotid and brachial blood flows in normal volunteers

The effects of nicardipine, 20 mg, three times daily, nicardipine slow release, 30 mg, twice daily and a placebo on brachial and carotid arteries diameters and flows have been investigated by the pulsed Doppler technique during a single blind and cross-over study performed in six healthy volunteers. Simultaneously, nicardipine plasma levels and relative bioavailability were determined. Nicardipine significantly increased brachial and carotid arteries diameters (by 16 and 10% respectively) and flows (by 60 and 35% respectively). These effects peaked after 4 h and lasted no longer than 6 h. Forearm vascular resistance was significantly decreased. Hence nicardipine dilated both large and small arteries. Nicardipine slow release elicited the same effects on brachial and carotid arteries diameters and flows as nicardipine. These effects peaked at 6 h and lasted up to 10 h. Although the profiles of the pharmacodynamic effects and of the kinetics of nicardipine were almost parallel in each individual after administration of both nicardipine formulations, there was no correlation between the nicardipine plasma relative bioavailability and its effects on brachial and carotid arteries blood flows when considering all subjects together.

Haemodynamic dose-response effects of i.v. nicardipine in coronary artery disease

The haemodynamic dose-response effects of the slow channel blocking agent nicardipine were evaluated in 10 male patients with angiographically confirmed coronary artery disease. At rest, following a similar control saline period, four doses of the drug (log cumulative dosage: 1.25, 2.5, 5.0 and 10.0 mg) were administered by i.v. infusion over a total duration of 40 min; haemodynamic variables were recorded in the 3-5 min following each 5 min infusion. During steady-state exercise the haemodynamic effects of the drug were evaluated by comparison of a control exercise period with observations made at the same workload (200-500 kpm) following the maximum cumulative dose (10 mg). Following the four i.v. infusions, the plasma nicardipine level increased log-linearly with the infused dose (r = 0.68). Compared with control measurements at rest after saline, these plasma concentrations (35 +/- 8 to 141 +/- 24 micrograms/l) resulted in a linear decrease in systemic blood pressure and vascular resistance with significant increase in cardiac index (maximum delta CI + 1.6 l min(-1) m(-2); P less than 0.01), stroke index (maximum delta SI + 11 ml/m2; P less than 0.01) and in pulmonary artery occluded pressure (maximum delta PAOP + 2 mm Hg; P less than 0.01). There was a significant increase in heart rate; the stroke work index was unchanged. During upright bicycle exercise the reduction in systemic blood pressure was accompanied by an increased exercise cardiac output without change in stroke index. The exercise pulmonary artery occluded pressure was unchanged compared with control observations, the stroke work index fell significantly (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)