Evaluation of changes in sympathetic nerve activity and heart rate in essential hypertensive patients induced by amlodipine and nifedipine

Heart Rate Variability in Patients with Hypertension: the Effect of Metabolic Syndrome and Antihypertensive Treatment

Metabolic syndrome (MetS) is a combination of factors which, collectively, increase cardiovascular risk to a greater extent than each of them separately. Previous studies showed high cardiovascular risk to be associated with autonomic nervous system dysfunction. The purpose of this study was to assess the effects of antihypertensive treatment on heart rate variability (HRV) in patients with hypertension (HTN), depending on cooccurrence of MetS. 118 patients with uncontrolled HTN were enrolled to the study. HRV was compared among patients with and without MetS (MetS [+], n = 70) at baseline and following 12 months antihypertensive treatment. The HRV indices measured from RR intervals recorded form using 24-hour ambulatory electrocardiography. The measured HRV domains were the standard deviation of the average of NN intervals [SDNN], square root of the mean of the sum of the squares of differences between adjacent NN intervals [rMSSD], percentage of NN50 [pNN50], low frequency [LF], high frequency [HF], total power of variance of all NN intervals [TP], and LF/HF ratio. Baseline parameters: SDNN, rMSSD, pNN50, and HF were significantly lower in the MetS[+] compared to the MetS[-] subgroup (p < 0.05). After a 12-month antihypertensive treatment, MetS[+] patients achieved a significant improvement in parameters: SDNN, rMSSD, pNN50, and TP (p < 0.05), while the changes in HRV observed in the MetS[-] subgroup were not statistically significant. The cooccurrence of HTN and other components of MetS is associated with disturbances of the autonomic balance. HTN control has a beneficial effect on HRV, with the effect being more evident in patients with MetS.

The effect of an L/N-type calcium channel blocker on intradialytic blood pressure in intradialytic hypertensive patients

BACKGROUND

Intradialytic hypertension (HTN), which is one of the poor prognostic markers in patients undergoing hemodialysis, may be associated with sympathetic overactivity. The L/N-type calcium channel blocker, cilnidipine, has been reported to suppress sympathetic nerves activity in vivo. Therefore, we hypothesized that cilnidipine could attenuate intradialytic systolic blood pressure (SBP) elevation.

METHODS

Fifty-one patients on chronic hemodialysis who had intradialytic-HTN (SBP elevation ≥10 mmHg during hemodialysis) and no fluid overload were prospectively randomized into two groups: control and cilnidipine groups. Cilnidipine group patients took cilnidipine (10 mg/day) for 12 weeks. The primary endpoint was the change in the intradialytic SBP elevation before and after the 12-week intervention.

RESULTS

Before the intervention, no differences were observed in age, sex or pre-dialytic SBP (148.5 ± 12.9 vs. 148.3 ± 19.3 mmHg) between the two groups. Intradialytic SBP elevation was unchanged in the control group. Cilnidipine significantly lowered the post-dialytic SBP with an attenuation of the intradialytic SBP elevation from 12.0 ± 15.4 mmHg to 4.8 ± 10.1 mmHg. However, the observed difference in the intradialytic SBP elevation by cilnidipine did not reach statistical significance (group×time interaction effect p = 0.25). Cathecolamine levels were unaffected by the intervention in both groups.

CONCLUSION

Cilnidipine lowers both the pre- and post-dialytic SBP and might attenuate intradialytic SBP elevation. Therefore, cilnidipine may be effective in lowering SBP during HD in patients with intradialytic-HTN.

Amlodipine and enalapril promote distinct effects on cardiovascular autonomic control in spontaneously hypertensive rats: the role of aerobic physical training

BACKGROUND

We compared the autonomic and hemodynamic cardiovascular effects of amlodipine and enalapril treatment associated with an aerobic physical training program on spontaneously hypertensive rats.

METHODS

Eighteen-week-old (n = 48) spontaneously hypertensive rats were assigned to one of two groups: sedentary (n = 24) and trained (n = 24) through a 10-week swimming training program. Each group was subdivided into three groups (n = 8): control (vehicle group), amlodipine (amlodipine group; 10 mg/kg per day) and enalapril (enalapril group; 10 mg/kg per day) (both for 10 weeks). We cannulated the femoral artery and vein of all animals for recording arterial pressure and injecting drugs, respectively. Autonomic assessment was performed by double blockade with propranolol and atropine, analysis of heart rate variability (HRV), systolic arterial pressure variability and baroflex sensitivity.

RESULTS

Arterial pressure reduction was more prominent in the sedentary and trained enalapril groups. Amlodipine sedentary group presented important autonomic adjustments characterized by a predominance of vagal tone in cardiac autonomic balance, increased HRV associated with sympathetic autonomic modulation reduction and increased vagal autonomic modulation, and increased baroflex sensitivity. All findings were not potentialized by physical training. In turn, the enalapril trained group, but not its sedentary counterpart, also had vagal tone prevalence in cardiac autonomic balance, increased HRV, increased baroflex sensitivity and decreased low-frequency band in systolic arterial pressure variability.

CONCLUSION

Amlodipine was more effective in promoting beneficial autonomic cardiovascular adaptations in sedentary animals. In contrast, enalapril achieved better autonomic results only when combined with aerobic physical training.

L/T-type calcium channel blocker reduces non-Gaussianity of heart rate variability in chronic kidney disease patients under preceding treatment with ARB

Introduction:

Increased sympathetic nerve activity has been suggested in patients with chronic kidney disease (CKD). Pathologic sympathetic activity can alter heart rate variability (HRV), and the altered HRV has prognostic importance, so that reducing sympathetic activity may be an important strategy. Novel nonlinear HRVs, including deceleration capacity (DC), have greater predictive power for mortality. We have recently proposed an increase in a non-Gaussianity index of HRV, λ_25s, which indicates the probability of volcanic heart rate deviations of departure from each standard deviation level, as a marker of sympathetic cardiac overdrive. L/T-type calcium channel blocker (L/T-CCB), azelnidipine, decreases sympathetic nerve activity in experimental and clinical studies.

Methods:

In 43 hypertensive patients with CKD under treatment with an angiotensin receptor blocker (ARB), we investigated whether 8-week add-on L/T-CCB treatment could restore HRV.

Results:

Means of all normal-to-normal intervals over 24 h (p<0.0001) and DC (p=0.002) increased, and λ_25s (p=0.001) decreased regardless of gender, age, renal function or blood pressure, while no significant changes were observed in the other HRVs.

Conclusions:

Reduction of λ_25s is useful to assess the effect of sympathoinhibitory treatment. Further studies are needed to investigate if the restoration of HRV is directly associated with the improvement of prognosis in patients with CKD.

Pathophysiological Mechanisms and Correlates of Therapeutic Pharmacological Interventions in Essential Arterial Hypertension

Treating arterial hypertension (HT) remains a hard task. The hypertensive patient is often a subject with several comorbidities and metabolic abnormalities. Clinicians everyday have to choose the right drug for the single patient among the different classes of antihypertensives. Apart from lowering blood pressure, a main therapeutic target should be that of counteracting all the possible pathophysiological mechanisms involved in HT itself and in existing/potential comorbidities. All the ancillary positive and negative effects of the administered drugs should be considered: in particular, since hypertensive patients are often glucose intolerant/diabetic, carrier of serum lipids disorder, have already developed atherosclerotic diseases and endothelial dysfunction, they should not be treated with drugs negatively interfering with these conditions but with molecules that, if possible, improve them. The main pathophysiological mechanisms and correlates of therapeutic pharmacological interventions in essential HT are reviewed here.

Long-acting dihydropyridine calcium-channel blockers and sympathetic nervous system activity in hypertension: a literature review comparing amlodipine and nifedipine GITS

Calcium-channel blockers (CCBs) constitute a diverse group of compounds but are often referred to as a single homogeneous class of drug and the clinical responses indiscriminately summarized. Even within the dihydropyridine subgroup, there are significant differences in formulations, pharmacokinetics, durations of action and their effects on blood pressure, heart rate, end organs and the sympathetic nervous system. Amlodipine and nifedipine in the gastrointestinal therapeutic system (GITS) formulation are the most studied of the once-daily CCBs. Amlodipine has an inherently long pharmacokinetic half-life, whereas, in contrast, nifedipine has an inherently short half-life but in the GITS formulation the sophisticated delivery system allows for once-daily dosing. This article is derived from a systematic review of the published literature in hypertensive patients. The following search terms in three main databases (MEDLINE, Embase, Science Citation Index) from 1990 to 2011 were utilized: amlodipine, nifedipine, sympathetic nervous system, sympathetic response, sympathetic nerve activity, noradrenaline, norepinephrine and heart rate. More than 1500 articles were then screened to derive the relevant analysis. As markers of sympathetic nervous system activation, studies of plasma norepinephrine concentrations, power spectral analysis, muscle sympathetic nerve activity and norepinephrine spillover were reviewed. Overall, each drug lowered blood pressure in hypertensive patients in association with only small changes in heart rate (i.e. <1 beat/min). Plasma norepinephrine concentrations, as the most widely reported marker of sympathetic nervous system activity, showed greater increases in patients treated with amlodipine than with nifedipine GITS. The evidence indicates that both these once-daily dihydropyridine CCBs lower blood pressure effectively with minimal effects on heart rate. There are small differences between the drugs in the extent to which each activates the sympathetic nervous system with an overall non-significant trend in favour of nifedipine GITS.

The significance of amlodipine on autonomic nervous system adjustment (ANSA method): a new approach in the treatment of hypertension

INTRODUCTION

Cardiovascular autonomic modulation is altered in patients with essential hypertension.

OBJECTIVE

To evaluate acute and long-term effects of amlodipine on cardiovascular autonomic function and haemodynamic status in patients with mild essential hypertension.

METHODS

Ninety patients (43 male, mean age 52.12 +/- 10.7) years with mild hypertension were tested before, 30 minutes after the first 5 mg oral dose of amlodipine and three weeks after monotherapy with amlodipine. A comprehensive study protocol was done including finger blood pressure variability (BPV) and heart rate variability (HRV) beat-to-beat analysis with impedance cardiography, ECG with software short-term HRV and nonlinear analysis, 24-hour Holter ECG monitoring with QT and HRV analysis, 24-hour blood pressure (BP) monitoring with systolic and diastolic BPV analysis, cardiovascular autonomic reflex tests, cold pressure test, mental stress test. The patients were also divided into sympathetic and parasympathetic groups, depending on predominance in short time spectral analysis of sympathovagal balance according to low frequency and high frequency values.

RESULTS

We confirmed a significant systolic and diastolic BP reduction, and a reduction of pulse pressure during day, night and early morning hours. The reduction of supraventricular and ventricular ectopic beats during the night was also achieved with therapy, but without statistical significance. The increment of sympathetic activity in early phase of amlodipine therapy was without statistical significance and persistence of sympathetic predominance after a few weeks of therapy detected based on the results of short-term spectral HRV analysis. All time domain parameters of long-term HRV analysis were decreased and low frequency amongst spectral parameters. Amlodipne reduced baroreflex sensitivity after three weeks of therapy, but increased it immediately after the administration of the first dose.

CONCLUSION

The results of the study showed that amlodipine affected autonomic modulation as a shift to sympathetic hyperactivity, but without statistical significance. In the selected group of patients with vagal predominance in sympathovagal balance, amlodipine increased sympathetic and decreases vagal activity. Therefore we conclude that amlodipine mostly exerts impact on autonomic function modulation in patients with vagal predominance in resting state.

Treatment of hypertension in patients with diabetes mellitus

Antihypertensive treatment in diabetes mellitus, especially in diabetics known to have cardiac autonomic neuropathy, may have to consider the status of the autonomic nervous system. In diabetic subjects with cardiac autonomic neuropathy, vagal activity during the night is often reduced. The reduction results in relative or absolute sympathetic activation, which could increase cardiovascular risk. Pathophysiological and clinical data suggests that antihypertensive treatment should reduce rather than induce sympathetic activity in this setting. Beta blocking agents, ACE inhibitors, calcium antagonists of verapamil or diltiazem type and selective imidazoline receptor agonists reduce sympathetic activity and, therefore, may have a beneficial effect in diabetic patients with disturbed sympathovagal balance.

Effects of valsartan or amlodipine alone or in combination on plasma catecholamine levels at rest and during standing in hypertensive patients

To compare the effects of valsartan and amlodipine alone or in combination on plasma norepinephrine (NE) at rest and standing for 10 minutes in patients with hypertension, 47 patients with a sitting diastolic blood pressure (BP) (DBP)>95 mm Hg and<110 mm Hg were randomized in a double-blind fashion to either valsartan or amlodipine. During the first 4 weeks of treatment, patients received a low dose of either valsartan (80 mg) or amlodipine (5 mg). The patients were force-titrated to the high dose of either drug (160 or 10 mg) for 4 weeks. After 8 weeks of therapy, those who still had a DBP>90 mm Hg (nonresponders) received combination therapy with the other drug, whereas patients with a DBP<90 mm Hg (responders) continued on monotherapy. Decreases in ambulatory BP and clinic systolic BP and DBP were significant (P<.05) after 8 weeks' therapy with no difference between the 2 groups. Amlodipine but not valsartan as monotherapy consistently increased NE levels at rest and enhanced NE levels during standing. Valsartan decreased basal NE in responders. Combination therapy with valsartan and amlodipine did not attenuate the rise in NE levels induced by amlodipine. This study indicates that therapy with amlodipine increases peripheral sympathetic basal tone and reactivity to standing in patients with hypertension, whereas valsartan does not. Combined therapy with amlodipine/valsartan did not attenuate the sympathetic activation induced by amlodipine. The hypotensive action of valsartan may be mediated in part by an inhibition of the sympathetic baroreflex in patients with hypertension.

Long-term calcium antagonist treatment of human hypertension with mibefradil or amlodipine increases sympathetic nerve activity

OBJECTIVES

Calcium antagonists are vasodilating drugs, which may cause reflex activation of the sympathetic nervous system with potentially untoward effects. We studied the effects of long-term treatment with amlodipine, a long-acting dihydropyridine-type calcium antagonist, and mibefradil, a phenylalkylamine-type calcium antagonist, on sympathetic nerve activity.

METHODS

Fourteen patients with primary hypertension participated in a double-blind, cross-over study comparing the effects of 6 weeks of treatment with mibefradil 100 mg daily and amlodipine 10 mg daily. Heart rate, direct arterial blood pressure and cardiac output by echocardiography were registered. Global sympathetic activity was estimated using a [3H]noradrenaline isotope dilution method with arterial and venous sampling; cardiac sympathetic activity was assessed indirectly by heart rate variability and tissue velocity echocardiography.

RESULTS

Both drugs lowered mean arterial pressure; the decrease was more pronounced with mibefradil (from 118 +/- 3 to 99 +/- 2 mmHg, compared to 118 +/- 3 to 104 +/- 2 mmHg for amlodipine, P < 0.01 between drugs). Mibefradil decreased heart rate (66 +/- 2 to 57 +/- 2 bpm), whereas amlodipine caused a slight increase (66 +/- 2 to 70 +/- 2 bpm; P < 0.001 between drugs) and tended to increase cardiac output. Noradrenaline spillover increased similarly with the two drugs, from 3.44 +/- 0.27 to 5.20 +/- 0.48 nmol/min per m2(P < 0.01) during mibefradil and to 5.72 +/- 0.49 nmol/min per m2 (P < 0.001) during amlodipine. There were minor effects on cardiac sympatho-vagal balance, but systolic and diastolic myocardial velocities were increased similarly by both drugs.

CONCLUSIONS

Mibefradil and amlodipine treatment increase global sympathetic nerve activity similarly during long-term treatment, despite opposite effects on heart rate. Increases in myocardial velocities suggest concomitant cardiac sympathetic activation.

Modified-release nifedipine: a review of the use of modified-release formulations in the treatment of hypertension and angina pectoris

Nifedipine is a dihydropyridine calcium channel antagonist with predominantly vasodilatory activity. Modified-release formulations of nifedipine are effective antihypertensive and antianginal therapies and are generally well tolerated. Among the available formulations, those that produce a gradual increase in plasma nifedipine concentration, which is then sustained over a 24-hour period, are preferred, as they cause a gradual onset of vasodilatation and avoid baroreflex sympathetic activation (for example, nifedipine gastrointestinal therapeutic system [GITS] and a Japanese controlled-release formulation). Modified-release nifedipine had beneficial effects on a number of markers of vascular function, and nifedipine GITS reduced the need for coronary procedures in patients with coronary artery disease. In patients with hypertension, nifedipine GITS and nifedipine retard had beneficial effects on the overall incidence of major cardiovascular events, as did nifedipine retard in patients with concurrent hypertension and coronary artery disease.

Amlodipine-induced reduction of oxidative stress in the brain is associated with sympatho-inhibitory effects in stroke-prone spontaneously hypertensive rats

Amlodipine is a dihydropyridine calcium channel blocker that is widely used for the treatment of hypertensive patients and has an antioxidant effect on vessels in vitro. The aim of the present study was to examine whether treatment with amlodipine reduced oxidative stress in the brains of stroke-prone spontaneously hypertensive rats (SHRSP). The animals received amlodipine, nicardipine or hydralazine for 30 days in their drinking water. Levels of thiobarbituric acid-reactive substances (TBARS) in the brain (cortex, cerebellum, hypothalamus, and brainstem) were measured before and after each treatment. Systolic blood pressure decreased to similar levels in the amlodipine-, nicardipine-, and hydralazine-treated groups. Urinary norepinephrine excretion was significantly reduced in SHRSP after treatment with amlodipine, but not with nicardipine or hydralazine. Levels of TBARS in the cortex, cerebellum, hypothalamus, and brainstem were significantly higher in SHRSP than in Wistar-Kyoto rats (WKY), and were reduced in amlodipine-treated, but not in nicardipine- or hydralazine-treated, SHRSP. Electron spin resonance spectroscopy revealed increased levels of reactive oxygen species in the brains of SHRSP, which were reduced by treatment with amlodipine. Intracisternal infusion of amlodipine also reduced systolic blood pressure, urinary norepinephrine excretion, and the levels of TBARS in the brain. These results suggested that oxidative stress in the brain was enhanced in SHRSP compared with WKY rats. In addition, antihypertensive treatment with amlodipine reduced oxidative stress in all areas of the brain examined and decreased blood pressure without a reflex increase in sympathetic nerve activity in SHRSP.

Sympatho-excitatory responses to once-daily dihydropyridines in young versus older hypertensive patients: amlodipine versus felodipine extended release

BACKGROUND

Once-daily dihydropyridines exert both indirect sympatho-excitatory and direct central sympatho-inhibitory effects. Age may affect this balance by influencing blood pressure (BP) or renin responses.

METHODS

We evaluated BP, sympathetic and cardiac responses after the first dose and after 8 weeks of treatment with placebo, amlodipine 5 mg/day or felodipine extended release (ER) 5 mg/day in 29 young (22-50 years) versus 37 older (60-77 years) hypertensive patients, using a double-blind, parallel group design.

RESULTS

In the young group, neither dihydropyridine dose decreased BP after the first dose and both caused decreases by 5-10 mmHg after chronic treatment. In the older group, felodipine ER decreased BP rapidly and amlodipine more gradually, and after chronic treatment, systolic BP decreased by 20-25 mmHg. Felodipine ER increased the heart rate by 5-10 bpm after the first dose in both age groups and caused persistent increases in the cardiac index (by 0.2 l/min per square metre) and the ejection fraction only in the older group. Amlodipine did not affect cardiac function in the young, and with chronic dosing decreased the heart rate by 3-5 bpm and the cardiac index by 0.2 l/min per square metre in the older group. In the young hypertensive patients, both dihydropyridines increased plasma norepinephrine (NE) after chronic dosing, with little effect after the first dose. In contrast, in the older group felodipine ER increased plasma NE after the first dose but not with chronic dosing, whereas amlodipine had no effect after the first dose, and after chronic dosing tended to decrease plasma NE.

CONCLUSION

We conclude that age is a major determinant not only of the BP but also of the cardiac and sympathetic responses to once-daily dihydropyridines.

Effects of amlodipine and lacidipine on heart rate variability in hypertensive patients with stable angina pectoris and isolated left ventricular diastolic dysfunction

OBJECTIVE

To estimate the influence of therapy with amlodipine (A) or lacidipine (L) on heart rate variability (HRV) time and frequency domain parameters in hypertensive patients with stable angina pectoris and isolated left ventricular diastolic dysfunction.

METHODS

After a 1-week washout period, the patients were randomized to receive amlodipine 10 mg (30 patients) or lacidipine 6 mg (30 patients) once-daily for 4 weeks. HRV parameters were determined over a period of 24 h, echocardiography and exercise test were performed before and after treatment.

RESULTS

All HRV time domain parameters after applying amlodipine did not change significantly. A reliable decrease only of the root mean square of differences between adjacent normal-to-normal intervals (RMSSD)-32.9 +/- 13 vs. 27.5 +/- 9-was noticed after treatment with lacidipine. In the lacidipine group, the change of RMSSD negatively correlated with the extent of ST segment depression during exercise testing (R = -0.43; P < 0.05). Both drugs reduced total power (A, 2234 +/- 1270 vs. 1813 +/- 889; L, 2205 +/- 1151 vs. 1825 +/- 896; P < 0.01), very low (A, 1451 +/- 733 vs. 1143 +/- 534; L, 1413 +/- 759 vs. 1213 +/- 616; P < 0.05), and low frequency power (A, 610 +/- 459 vs. 447 +/- 321; L, 569 +/- 323 vs. 442 +/- 241; P < 0.01). After amlodipine, high frequency power remained unchanged, whereas low-high frequency ratio decreased (4.54 +/- 1.72 vs. 3.77+/-1.73; P < 0.05). After lacidipine, high frequency power decreased (178.8 +/- 153.2 vs. 132.1 +/- 79.3; P < 0.05), whereas the ratio of low frequency to high frequency did not change.

CONCLUSIONS

Amlodipine and lacidipine reduce the influence of humoral control and sympathetic autonomic nervous system activity. The autonomic balance becomes shifted toward the increased vagal activity only by amlodipine.

Effect of the renin–angiotensin system or calcium channel blockade on the circadian variation of heart rate variability, blood pressure and circulating catecholamines in hypertensive patients

OBJECTIVE

To determine the effects of 8 weeks of therapy with amlodipine, ramipril or telmisartan on the autonomic system over 24 h in hypertensives.

METHODS

After a placebo run-in, 57 patients were included in a prospective randomized open-label design protocol for therapy with amlodipine (5 mg for 4 weeks followed by 10 mg for 4 weeks, n = 22), or ramipril (2.5 mg for 1 week, 5.0 mg for 3 weeks and 10 mg for 4 weeks, n = 17) or telmisartan (80 mg for 8 weeks, n = 18). Autonomic functions were assessed by norepinephrine (NE) and epinephrine (E), as well as by the spectral analysis of heart rate variability (HRV).

RESULTS

The 24-h ambulatory blood pressure, plasma NE and HRV demonstrated the characteristic day-night circadian rhythm in hypertensives. Higher values for SBP and DBP and for NE levels, as well as for spectral analysis components - low frequency band (LF) and low frequency/high frequency (LF/HF) ratio - were found during the day, whereas the HF was higher during the night. In patients treated with amlodipine, the HF decreased significantly during the night, while the LF and the LF/HF ratio increased during the day in association with the rise in NE. The therapy with telmisartan did increase the HF during the night and the day, while ramipril did not influence all HRV components during the night but significantly increased the HF, and decreased the LF/HF ratio during the day. No changes were observed in plasma NE with telmisartan or ramipril, but a 50% increase in NE levels throughout the 24-h period was found in amlodipine-treated patients.

CONCLUSION

These data suggest a sympathetic activation during the day and a decrease in parasympathetic activity during the night after therapy with amlodipine, correlated with increases in plasma NE. In contrast, the therapy with telmisartan significantly increased parasympathetic activity without changes in NE during the night and day. The therapy with ramipril increased the parasympathetic activity only during the day.

Effects of a New Calcium Channel Blocker, Azelnidipine, on Systemic Hemodynamics and Renal Sympathetic Nerve Activity in Spontaneously Hypertensive Rats

Antihypertensive treatment with dihydropyridine calcium channel blockers elicits sympathetic nerve activation, which may contribute to cardiovascular events. However, recent clinical studies showed that treatment with azelnidipine, a new dihydropyridine calcium channel blocker, significantly reduced blood pressure in hypertensive patients while either maintaining or actually decreasing heart rate (HR). In this study, we examined the effects of azelnidipine and amlodipine on systemic hemodynamics and renal sympathetic nerve activity (RSNA) in anesthetized spontaneously hypertensive rats (SHR). We also examined the effects of these agents on baroreflex functions by infusing phenylephrine (30 microg/kg/min, i.v.) and sodium nitroprusside (10 microg/kg/min, i.v.) into azelnidipine- or amlodipine-treated SHR. Fifty min after administration of azelnidipine (10 microg/kg/min for 10 min, i.v.), mean arterial pressure (MAP) significantly decreased from 153+/-5 to 122+/-5 mmHg; however, HR and integrated RSNA did not change significantly (from 352+/-9 to 353+/-10 beats/ min and 115+/-5% of baseline, respectively). Infusion of amlodipine (50 microg/kg/min for 10 min) elicited similar effects on MAP (from 152+/-5 to 120+/-4 mmHg). However, amlodipine significantly increased HR (from 351+/-9 to 375+/-11 beats/min) and integrated RSNA (165+/-5% of baseline). Analyses of baroreflex function curves revealed that azelnidipine-treated rats showed a smaller baroreflex function than amlodipine-treated rats (p<0.05). These data suggest that azelnidipine possesses sympathoinhibitory effects, which may be one reason why it had less pronounced effects on HR in hypertensive patients.

Comparison of once-daily nifedipine controlled-release with twice-daily nifedipine retard in the treatment of essential hypertension

AIMS

Nifedipine is a short-acting calcium antagonist formulated into several different oral preparations, each of which may have different effects on haemodynamics and autonomic nervous function. We compared the effects of nifedipine controlled-release (CR) and nifedipine retard on 24-h blood pressure, heart rate, rate-pressure product, and power spectral measures of heart rate variability in patients with essential hypertension.

METHODS

After 4 weeks of a drug-free period, 25 patients were randomized to receive either once-daily treatment with nifedipine CR (20-40 mg daily; 12 patients) or twice-daily treatment with nifedipine retard (20-40 mg daily; 13 patients) for 12 weeks. The ambulatory blood pressure, heart rate, and ECG R-R intervals were measured during a 24-h period using a portable recorder (TM-2425) at the end of the drug-free and the treatment periods. A power-spectral analysis of R-R intervals was performed to obtain the low-frequency (LF) and high-frequency (HF) components.

RESULTS

Nifedipine CR and nifedipine retard reduced 24-h blood pressure significantly by 15.9 +/- 3.2 (SE)/8.7 +/- 1.4 mmHg and by 10.9 +/- 2.8/9.4 +/- 1.7 mmHg, respectively, after the 12-week treatment. Nifedipine CR did not change the 24-h heart rate significantly, while nifedipine retard increased it significantly by 3.9 +/- 2.1 beats min(-1). Nifedipine CR produced a significant reduction in rate-pressure product throughout a 24-h period, while nifedipine retard did not change the rate-pressure product significantly. In addition, nifedipine retard significantly decreased the 24-h and daytime average values of the LF and HF components, while nifedipine CR affected the nighttime LF component alone and did not change the HF component throughout a 24-h period.

CONCLUSIONS

These results demonstrate that both nifedipine CR and nifedipine retard are effective as antihypertensive agents, but nifedipine CR has less influence on the autonomic nervous system and heart rate than nifedipine retard.

Antihypertensive drugs: an overview

For most patients with systemic hypertension, long-term drug treatment is indicated and is beneficial. There is overwhelming evidence to suggest that antihypertensive drugs offer protection against complications of hypertension. Whereas nondrug therapeutic options should be implemented in all patients, a vast majority will require pharmacological treatment to achieve goal blood pressure levels. Fortunately, a number of drugs are available to accomplish successful treatment of hypertensive disorders. While it is conventional to initiate treatment with a single drug, a suitable combination of drugs is often required to control the blood pressure effectively. Although diuretics and beta-blockers are effective and well tolerated, other classes of drugs are being increasingly used as the initial choice of therapy for hypertension. Every class of antihypertensive drugs offer advantages and some disadvantage; the physician should weigh the benefits and risks in selecting one drug over another. While the clinical parameters are followed in the management of patients with hypertension, it is also necessary to monitor the patients' biochemical profile periodically in order to modify and adjust the therapy accordingly. A careful selection of drug therapy along with close follow-up offers the best prospect to reduce the burden of morbidity and mortality in hypertension. This article provides an overview of drugs in the management of patients with hypertension.

Amlodipine improves vascular function in patients with moderate to severe hypertension

The long-term effects of amlodipine, a calcium channel blocker, were examined in patients with moderate to severe hypertension. Eighteen never-treated patients with moderate to severe essential hypertension (49 +/- 8 years) were studied. In all patients, forearm blood flow (FBF) was measured by plethysmography before and 6 months after amlodipine treatment. Endothelium-nondependent and endothelium-dependent vasodilations were assessed by intrabrachial infusion of sodium nitroprusside (SNP) and acetylcholine (ACh), respectively. FBF modification by vitamin C, an oxygen radical scavenger, was also assessed under ACh infusion. The results were compared with those of 13 normal subjects. Blood pressure was significantly lowered (from 176 +/- 17/97 +/- 13 to 144 +/- 12/82 +/- 10 mm Hg) after treatment (P < 0.01). Forearm vascular resistance was increased in the hypertensive patients before treatment; however, it was normalized after treatment during SNP infusion and was improved during ACh infusion. Since vitamin C improved FBF under ACh infusion both before and after the amlodipine treatment, it is suggested that the production of free radicals was not canceled by amlodipine. The analysis of heart rate variability showed that amlodipine does not activate sympathetic nerve function. Therefore, amlodipine is effective in lowering blood pressure associated with the improvement of vascular function, and is suggested to be an effective antihypertensive agent for patients with moderate to severe hypertension.

Overexpression of eNOS in RVLM improves impaired baroreflex control of heart rate in SHRSP. Rostral ventrolateral medulla. Stroke-prone spontaneously hypertensive rats

We previously demonstrated that the overexpression of endothelial nitric oxide synthase (eNOS) in the rostral ventrolateral medulla (RVLM) decreases blood pressure, heart rate (HR), and sympathetic nerve activity and that these effects are enhanced in stroke-prone spontaneously hypertensive rats (SHRSP). The aim of this study was to determine if an increase in NO production in the RVLM caused by the overexpression of eNOS improves the impaired baroreflex control of HR in SHRSP. We transfected adenovirus vectors encoding eNOS (AdeNOS) into the RVLM of SHRSP or Wistar-Kyoto rats (WKY). Mean arterial pressure and HR were measured by a radio-telemetry system in the conscious state. Reflex changes in HR were elicited by intravenous infusion of either phenylephrine, sodium nitroprusside, or hydralazine at day 7 after the gene transfer. The maximum gain of the baroreflex control of HR was significantly decreased in SHRSP compared with WKY. Overexpression of eNOS in the RVLM of SHRSP improved the impaired maximum gain of the baroreflex control of HR. After treatment with atropine, the maximum gain was still significantly greater in SHRSP in the AdeNOS-transfected group than in the nontransfected group, although it was decreased in both groups. In contrast, after treatment with metoprolol, the maximum gain did not differ between the two groups. These results indicate that an increase in NO production in the RVLM improves the impaired baroreflex control of HR in SHRSP and that these effects may have resulted from a cardiac sympathoinhibitory effect of NO in the RVLM of SHRSP.

Heart rate in hypertensive patients treated with ACE inhibitors and long-acting dihydropyridine calcium antagonists

Rapid heart rate (HR) has been reported to be a predictor of cardiovascular morbidity and mortality in hypertensive patients. The aim of this study was to evaluate the effect of ACE inhibitors and long-acting dihydropyridine calcium antagonists on clinic and ambulatory HR in patients with essential hypertension. We selected 292 hypertensive patients treated with ACE inhibitors and 198 hypertensive patients treated with dihydropyridine calcium antagonists. Groups were balanced for age, gender, body mass index, baseline blood pressure (BP) and HR, treatment duration and occupation. Patients had been submitted to clinic evaluation and noninvasive monitoring of BP and HR at baseline and during chronic therapy. Clinic and ambulatory BP were significantly and similarly reduced in patients treated with ACE inhibitors and calcium antagonists. Globally, clinic and 24-h HR were significantly reduced in patients treated with ACE inhibitors and remained unchanged in those treated with calcium antagonists. When patients were grouped according to baseline clinic HR (< 65 beats/min, 65-74 beats/min, 75-84 beats/min, and >85 beats/min), ACE inhibitors did not significantly change HR in subjects with baseline clinic HR <74 beats/min but significantly reduced clinic, 24-h, daytime and nighttime HR in those with baseline HR >75 beats/min and particularly in those with baseline HR >85 beats/min. Calcium antagonists did not significantly change clinic, 24-h, daytime and nighttime HR in various subgroups. Our study shows that ACE inhibitors reduce both clinic and ambulatory HR in hypertensive patients with faster HR, who seem to be at higher risk, and that long-acting dihydropyridine calcium antagonists do not induce significant changes in HR during chronic treatment (neither decrease nor increase). Whether this aspect is associated with a better prognostic impact of ACE inhibitors in essential hypertension should be determined in prospective studies.

Effects of selective angiotensin II receptor blockade on sympathetic nerve activity in primary hypertensive subjects

OBJECTIVE

The role of the renin-angiotensin system in the regulation of sympathetic nervous activity in human hypertension was evaluated in patients with moderate primary hypertension. For that purpose, the effects of selective angiotensin II (ANG II) receptor blockade by valsartan on sympathetic outflow to the muscle vascular bed and hemodynamic parameters were examined. Results were compared with the effects of the peripherally acting calcium antagonist amlodipine.

DESIGN

Eighteen hypertensive but otherwise healthy subjects were examined in a double-blind, placebo-controlled, cross-over protocol receiving either valsartan or amlodipine or placebo for 7 days in a randomized sequence. Treatment periods were separated by washout periods of 2 weeks.

METHODS

At the seventh day of treatment, blood pressure, heart rate, muscle sympathetic nerve activity (MSNA), norepinephrine, renin and angiotensin were measured during resting conditions. Additionally, parameters were measured after administration of negative pressure of -15 mmHg to the lower part of the body and after a cold pressor test.

RESULTS

Both antihypertensive drugs significantly decreased oscillometrically measured systolic blood pressure and diastolic blood pressure without any difference in effect. While valsartan did not affect the heart rate at rest, amlodipine increased it significantly. Likewise, MSNA was significantly enhanced by amlodipine but not by valsartan. Only ANG II receptor blockade increased renin and angiotensin levels.

CONCLUSIONS

Selective ANG II receptor blockade not only decreases blood pressure, but also shifts the baroreflex set-point for the initiation of counter-regulatory reflex responses of heart rate and blood pressure towards normal blood pressure levels. Thus, data suggest that ANG II plays a pathogenetic role in the elevation of the baroreflex set point in primary hypertensive subjects.

Differential effects of a long-acting angiotensin converting enzyme inhibitor (temocapril) and a long-acting calcium antagonist (amlodipine) on ventricular ectopic beats in older hypertensive patients

We studied differences in the effects of a long-acting angiotensin-converting enzyme (ACE) inhibitor (temocapril) and a long-acting calcium channel blocker (amlodipine) on ventricular ectopic beats (VEB) in relation to sympathetic nerve activity in 46 patients with essential hypertension. We performed 24-h Holter electrocardiography and ambulatory blood pressure (BP) monitoring simultaneously, and examined blood samples during the baseline, temocapril and amlodipine treatment periods. The ambulatory BP was lower in the amlodipine period than in the temocapril period. However, the number of VEB was significantly increased in the amlodipine period compared to that in the baseline period (11.9 vs. 7.4/day, p<0.05). In the temocapril period, the number of VEB was not significantly increased compared to that in the baseline period (8.6 vs. 7.4/day, p=0.30). Ambulatory heart rate (HR) was significantly increased in the amlodipine period compared to that in the baseline period (24-h HR: 70 vs. 66 bpm, p<0.001; daytime HR: 75 vs. 71 bpm, p<0.001; nocturnal HR: 60 vs. 58 bpm, p<0.05). Plasma norepinephrine (NE) also was significantly increased in the amlodipine period compared to that in the baseline period (457 vs. 369 pg/ml, p<0.001). However, when patients receiving amlodipine were divided into a high dose group (8.6 +/- 1.2 mg/day) and a low dose group (4.6 +/- 1.2 mg/day), increases in HR and plasma NE levels were found only in the high dose group. These results indicate that amlodipine is effective at lowering BP in older hypertensives, although it may increase VEB, especially when given at a high dose.

Clinical pharmacology of antihypertensive drugs

Systemic hypertension is a major public health problem and is perhaps the most common chronic disorder in most societies. Most patients with vascular disease report hypertension in their medical history. Irrespective of the specialty that one practices, every physician will likely encounter patients with systemic hypertension. Unfortunately, an overwhelming number have so-called "primary" or "essential" hypertension for which a cure has yet to be found. Fortunately, excellent therapy is available to control this modern malady. The field of hypertension continues to evolve rapidly, particularly in the field of therapy. During the past two decades, the treatment of hypertension has moved from a cookbook approach to more scientifically based individualized management. This paradigm shift requires the practitioner to acquire sufficient knowledge about individual drugs and how they work in a given patient. Rapid expansion of available drugs has placed a burden on the clinician to keep up with these advances. We hope that the discussions contained herein will ease that burden somewhat and make the treatment options less cumbersome. This article addresses the practical issues related to selection of antihypertensive drugs and provides an overview of advantages and disadvantages of individual drug classes. The reader should also refer to the JNC VI document [1] to further understand the selection of drug therapy based upon compelling indications. The ultimate aim of hypertension management should always be to achieve target or goal blood pressure levels.

Comparison of the effects of amlodipine and losartan on 24-hour ambulatory blood pressure in hypertensive patients

Effects of amlodipine (AML), a long-acting calcium antagonist, and losartan (LOS), an angiotensin II receptor antagonist, on 24-hr blood pressure profile were compared in 15 patients with essential hypertension. After 4 weeks of placebo period, the patients were treated with AML or LOS in a random crossover design for 12-16 weeks each. Either drug was given once daily at 0800 and the doses were titrated so that the office blood pressure was reduced lower than 140/90mmHg. At the end of each period, 24-hr blood pressure was monitored. Average office blood pressure was lowered from 158 +/- 2/ 98 +/- 2 mmHg to 134 +/- 1/87 +/- 1 mmHg by AML and 134 +/- 2/88 +/- 1 mmHg by LOS. Average 24-hr blood pressure was also reduced from 144 +/- 3/ 92 +/- 2 mmHg to 131 +/- 2/84 +/- 2 mmHg by AML and 135 +/- 3/85 +/- 2 mmHg by LOS. The averaged 24-hr systolic blood pressure was significantly lower in AML than in LOS (p < 0.05). Then, the 24-hr blood pressure was analyzed for four segments; morning (0530-0900 h), daytime (0930-1800 h), evening (1830-2300 h) and night (2330-0500 h). Although the daytime blood pressure was comparable between AML and LOS, systolic blood pressure in the evening and morning hours were lower in AML than in LOS (133 +/- 2 vs. 138 +/- 3mmHg,p<0.01; 129 +/- 3 vs. 134 +/- 4,p<0.05). Troughtopeakratio of antihypertensive effect on systolic blood pressure was significantly greater in AML than in LOS (62 +/- 5% vs. 55 +/- 4%, p < 0.05). Either drug did not cause reflective increase in pulse rate over 24 hours. These results suggest that both AML and LOS are equally effective in lowering daytime blood pressure without eliciting reflex tachycardia, however, the antihypertensive effect of AML lasts longer than that of LOS. Such information seems important to achieve 24-hr blood pressure control using these drugs.

Central sympathoinhibitory effects of calcium channel blockers

It is generally assumed that the arterial vasodilation induced by inhibition of Ca(2+) influx into vascular smooth muscle cells represents the main mechanism for the hypotensive effect of dihydropyridine calcium channel blockers. Increases in sympathetic tone have been related to activation of the arterial baroreflex by rapid lowering of blood pressure. This review highlights new findings in two areas. First, in animal studies, direct central administration of dihydropyridines such as nifedipine or amlodipine lowers sympathetic nerve activity and thereby blood pressure. Peripheral administration of nifedipine or amlodipine at low rates appears to result in gradual accumulation of drug in the central nervous system, and also causes lowering of sympathetic nerve activity and thereby lowering of blood pressure (rather than by arterial vasodilation). Second, in hypertensive humans treated with long-acting dihydropyridines and presumably little activation of the arterial baroreflex, some studies have demonstrated lowering of sympathetic activity (as assessed by plasma norepinephrine), but others reported increases (as assessed by plasma norepinephrine or microneurography). This sympathoexcitatory response may be due to activation of the renin-angiotensin system, particularly at higher doses.

Energy and substrate metabolism in patients with chronic extensive graft-versus-host disease

BACKGROUND

Allogeneic stem cell transplantation is frequently complicated by graft-versus-host disease (GVHD). Weight loss is one of the characteristic features of GVHD. The etiology of weight loss in GVHD is not completely understood.

METHODS

We measured resting energy expenditure (REE) and substrate oxidation rates by indirect calorimetry in patients with stable chronic extensive GVHD under immunosuppressive therapy (n=13) and sex-, age-, height-, and weight-matched healthy controls (n=13) in order to evaluate metabolic changes in these patients. Measurements were done on day 518+/-261 after allogeneic stem cell transplantation in the postabsorptive state. Serum concentrations of glucagon, norepinephrine, tumor necrosis factor-alpha, interleukin-6, and free fatty acids were determined.

RESULTS

Patients showed a maximum weight loss of 22% during their course of GVHD; nevertheless, they regained 15% of total body weight (TBW) during successful treatment of GVHD. Indirect calorimetry showed an increase in REE per kilogram of TBW (patients, 21.8+/-3.1 kcal/kg TBW/day; controls, 19.9+/-2 kcal/kg TBW/day; P<0.05). Respiratory quotient (patients, 0.79+/-0.04, controls, 0.86+/-0.04; P<0.005) and non-protein respiratory quotient (0.78+/-0.05 and 0.87+/-0.05, respectively; P<0.005) were decreased in patients. GVHD patients had elevated serum glucagon and norepinephrine concentrations, whereas tumor necrosis factor-alpha and interleukin-6 were in the normal range.

CONCLUSIONS

Patients with chronic extensive GVHD show an increase in REE and alterations in fat and carbohydrate oxidation rates. These changes seem to be the result of increased action of glucagon and norepinephrine.

Antihypertensive drugs and sympathetic nervous system

Several studies have demonstrated that essential hypertension is accompanied by sympathetic activation, which contributes to blood pressure elevation. Sympathetic activation also has adverse consequences in hypertensive patients beyond initiating blood pressure elevation. There is evidence that neural vasoconstriction has metabolic effects in skeletal muscle, impairing glucose delivery to muscles. In the liver, retarding of post prandial clearance of lipids contributes to hyperlipidemia. Cardiac sympathetic activation is a probable cause of sudden death in hearth failure. A trophic effect of sympathetic activation on cardiovascular growth is also likely, contributing to the development of left ventricular hypertrophy. Consequently, one of the major aims of antihypertensive therapy should be to attenuate sympathetic tone. It is possible that, among the antihypertensive drugs available, those inhibiting the sympathetic nervous system might best reduce cardiovascular risk.

Sympathoinhibitory and depressor responses to long-term infusion of nifedipine in spontaneously hypertensive rats on high-salt diet

Short-term (by hour) intracerebroventricular (i.c.v.) or i.v. infusion of nifedipine at low rates evokes parallel decreases in renal sympathetic nerve activity (RSNA) and blood pressure (BP) in spontaneously hypertensive rats (SHR). In the present study, effects of long-term administration of nifedipine on BP and control of sympathetic tone were examined in SHR on a high-salt (8%) diet. From 6 to 8 weeks of age, for 2 weeks concomitant with taking a high-salt diet, rats were also treated with subcutaneous infusion of nifedipine at 10, 50, or 100 microg/kg/h or vehicle solvent as control using osmotic minipumps. At the end of the 2-week treatment period, mean arterial pressure (MAP), heart rate (HR), and RSNA at rest and in response to air-jet stress, i.c.v. injection of the alpha-adrenoceptor agonist guanabenz (25 microg), and i.v. injection of the ganglionic blocker hexamethonium were recorded in conscious rats. In rats on nifedipine 50 or 100 microg/kg/h, resting MAP was significantly lower (136+/-4 or 130+/-4 vs. 145+/-2 mm Hg in control rats, p < 0.05 for both), the sympathoinhibitory and depressor responses to i.c.v. guanabenz were significantly decreased, and the absolute decreases in MAP in response to i.v. injection of hexamethonium were significantly smaller. Sympathoexcitatory and pressor responses to air-jet stress, however, were not affected by nifedipine. Infusion of nifedipine at the three rates for 2 weeks caused concentrations of plasma nifedipine in a dose-related manner. Nifedipine was not detected in tissues of rats treated with 10 microg/kg/h nifedipine but was present in brain and other tissues of rats treated with nifedipine at the two higher rates. Thus in SHR on high-salt intake long-term treatment with nifedipine at 50 or 100 microg/kg/h decreased resting BP and the sympathetic component in BP control. In addition to possible peripheral effects, long-term administration of nifedipine may also act centrally to decrease sympathetic activity and BP, likely by increasing activity in central pathways involving sympathoinhibition, but not in pathways involving sympathoexcitation as evaluated by air-stress.

Effects of different dihydropyridine calcium antagonists on plasma norepinephrine in essential hypertension

OBJECTIVE

The aim of this study was to compare the chronic effects of four dihydropyridine calcium antagonists with different pharmacologic characteristics, amlodipine, felodipine, lacidipine and manidipine,on blood pressure (BP), heart rate (HR) and plasma norepinephrine (NE) levels in patients with mild to moderate essential hypertension.

METHOD

After a 4-week placebo period, 60 patients of both sexes were randomly administered amlodipine 5-10 mg once daily (o.d.) (n = 15); felodipine 5-10 mg o.d. (n = 15); lacidipine 4-6 mg o.d. (n = 15); manidipine 10-20 mg o.d. (n = 15), for 24 weeks, according to a double blind, parallel group design. Initially, for the first 2 weeks, the lowest dose of each drug was used, then higher doses were administered if sitting diastolic blood pressure (DBP) was > 90 mmHg. BP, HR and plasma NE were evaluated at the end of the placebo and active treatment periods. NE was assessed at trough, at peak and after 12 h from drug ingestion.

RESULTS

Administration of all four drugs reduced clinic BP to the same level after 24 weeks, whereas HR increased only with felodipine (+ 3.1 bpm; P< 0.05). Significant increases in plasma NE levels were observed after chronic therapy with amlodipine and felodipine (+ 34.9 and + 39.4% respectively; P< 0.01 versus placebo) but not with lacidipine (+ 7.1%, NS) and manidipine (+ 2.9%, NS).

CONCLUSIONS

These findings suggest that sympathetic activation occurred during chronic treatment with amlodipine and felodipine, whereas manidipine and lacidipine did not increase plasma noradrenaline at the times measured. The reasons for this difference are unclear; they could be related to the different pharmacological characteristic of the two drugs, lacidipine and manidipine.

Sympathoinhibition by central and peripheral infusion of nifedipine in spontaneously hypertensive rats

The present study assessed whether central mechanisms may contribute to the hypotensive effect of the calcium channel blocker nifedipine. In conscious, spontaneously hypertensive rats (SHR) on a high-salt diet, hemodynamic (mean arterial pressure [MAP] and heart rate) and sympathetic (renal sympathetic nerve activity) responses to low, central, intracerebroventricular infusion rates (25 microg. kg(-1). h(-1) for 2 hours) and peripheral intravenous rates (50 microg. kg(-1). h(-1) for 3 hours and then 100 microg. kg(-1). h(-1) for 2 hours) of nifedipine were evaluated. The distribution of nifedipine in the blood and tissues was assessed at the end of the infusions. Nifedipine significantly inhibited renal sympathetic nerve activity and lowered MAP in SHR beginning 30 minutes after the start of the intracerebroventricular infusion. The decrease of MAP by intravenous infusion began at 60 minutes and was more profound with 100 microg. kg(-1). h(-1). Inhibition of sympathetic activity preceded and then paralleled the decrease in blood pressure; it occurred earlier with central (15 to 30 minutes) than with peripheral (30 to 60 minutes) infusion. Intravenous infusion resulted in concentrations of nifedipine in brain structures (brain stem, midbrain, and cortex) that were 30% to 40% of those in the heart, kidneys, and liver. From the hemodynamic and sympathetic responses and the distribution of nifedipine into the central nervous system, we conclude that the peripheral infusion of nifedipine at relatively low rates may evoke a hypotensive response in SHR, not only via peripheral mechanisms, but also through central mechanisms, which will lead to an inhibition of sympathetic outflow and, therefore, a lowering of blood pressure.

Amlodipine, a long-acting calcium channel blocker, attenuates morning blood pressure rise in hypertensive patients

1. The effects of once-daily calcium channel blockers with different plasma half-lives on diurnal blood pressure changes were examined in hypertensive patients. 2. Patients with essential hypertension, nine men and 13 women aged 61 +/- 2 years, were treated with amlodipine or nitrendipine in a random cross-over design for 12-16 weeks each. The study drugs were given once daily as monotherapy (n = 8) or in combination with other classes of antihypertensive drugs (n = 14). The plasma half-life of amlodipine is as long as 36 h, while that of nitrendipine is 10 h. At the end of each treatment period, 24 h ambulatory blood pressure and pulse rate were monitored. 3. Average office blood pressure was comparably controlled below 140/90 mmHg by either amlodipine or nitrendipine, both in the monotherapy and the combination therapy groups; however, pulse rate was greater in nitrendipine than in amlodipine either in the monotherapy (by 6 b.p.m., P < 0.05) or in the combination therapy (by 5 b.p.m., P < 0.01). 4. In 24 h blood pressure monitoring, morning (05.30-09.00 h) blood pressure was higher in nitrendipine than in amlodipine by 6/4 mmHg in the monotherapy (P < 0.05) and by 7/5 mmHg in the combination therapy (P < 0.03), although the blood pressure in the remainder of the 24 h did not differ between the two treatment periods. In addition, pulse rate in the daytime (09.30-18.00 h) was greater in nitrendipine than in amlodipine by 6 b.p.m. in the monotherapy (P < 0.01) and by 7 b.p.m. in the combination therapy (P < 0.02). 5. These results suggest slow pharmacokinetics of amlodipine provides an advantage in controlling morning blood pressure and mitigating reflex activation of the sympathetic nervous system.

Calcium antagonists "some agents lower blood pressure and still put the heart at risk"?

The 1,4 dihydropyridine calcium antagonists have several properties that theoretically make them attractive for treatment of hypertension and prevention as well as management of coronary artery disease (CAD). However, some of them appear to have actions that are detrimental for outcome. This brief review will first address the different subclasses of dihydropyridines, then outline differences between these subclasses which may impact on outcome in CAD and hypertension, and the last part will review present evidence for differences in cardiac outcome.

Effects of amlodipine and cilnidipine on cardiac sympathetic nervous system and neurohormonal status in essential hypertension

N-Type calcium channel antagonists may suppress sympathetic activity. The purpose of this study was to assess the effects of amlodipine and cilnidipine on the cardiac sympathetic nervous system and the neurohormonal status of essential hypertension. 123I-metaiodobenzylguanidine (MIBG) cardiac imaging was performed and blood samples were taken to determine plasma renin activity and plasma norepinephrine concentration before and 3 months after drug administration in 47 patients with mild essential hypertension. Twenty-four of the patients were treated with 5 to 10 mg/d of amlodipine; the other 23 were treated with 10 to 20 mg/d of cilnidipine. For comparison, 12 normotensive subjects were also studied. No significant differences were found in the basal characteristics between the 2 hypertensive groups. In both hypertensive groups, both the systolic and diastolic blood pressures were significantly reduced to similar levels 3 months after drug treatment. Before the drug treatment, the 2 hypertensive groups had a significantly higher washout rate and lower heart-to-mediastinum (H/M) ratio compared with the normotensive subjects. The H/M ratio significantly increased (P<0.05) in combination with a decreased washout rate (P<0.02) after drug treatment in the cilnidipine group. In the amlodipine group, a significant decrease in washout rate (P<0. 04) was noted, without an increase in the H/M ratio. However, no significant changes were found in plasma renin activity and plasma norepinephrine concentration in either group. Thus, in patients with essential hypertension, cilnidipine suppressed cardiac sympathetic overactivity and amlodipine had a little suppressive effect. Cilnidipine may provide a new strategy for treatment of cardiovascular diseases with sympathetic overactivity.

Heart rate as a risk factor for atherosclerosis and cardiovascular mortality: the effect of antihypertensive drugs

The aim of this review is to highlight the importance of heart rate (HR) as a risk factor for cardiovascular disease, and to discuss the classes of drugs which can be potentially useful in clinical conditions in which an elevated HR may be present. Numerous studies have shown that high resting HR is prospectively related to the development of atherosclerosis and of cardiovascular events. This relationship was independent of other major risk factors for atherosclerosis and was observed in the general population, in elderly people, in hypertensive cohorts and in patients with myocardial infarction or heart failure. The clustering of several risk factors in individuals with fast heart rate may explain why cardiovascular morbidity is higher in individuals with tachycardia. Sympathetic overactivity seems to be responsible for both the increase in HR, blood pressure and the metabolic abnormalities. Experimental studies in monkeys have shown that HR can also exert a direct atherogenetic action on the arteries through increased wall stress. Moreover, tachycardia can favour the occurrence of ventricular arrhythmias and sudden death. Reduction of HR appears as an additional goal of antihypertensive therapy. If fast HR in hypertension is a marker of increased sympathetic tone, agents which decrease HR through a decline of sympathetic outflow should be particularly efficacious. Beta-blockers retard the development of coronary atherosclerosis in cholesterol-fed monkeys and have proven to be beneficial in patients with myocardial infarction or with heart failure, but their efficacy appear limited in hypertension, probably on account of their unfavourable metabolic profile. Phenylalkylamines are devoid of this untoward effect, and seem to act also through inhibition of sympathetic discharge from the CNS. Mibefradil, a more recent calcium antagonist that selectively blocks voltage-dependent T-type calcium channels decreases HR without affecting left ventricular contractility. New drugs with agonistic properties at the I1-imidazoline receptors of the rostral ventrolateral medulla are effective in reducing blood pressure and HR by inhibiting the sympathetic outflow and improved metabolic parameters in obese or fructose-fed rats. The goal of antihypertensive therapy in the future will be to prevent or reverse those functional abnormalities which accompany the hypertensive condition. In patients with tachycardia the reduction of HR appears a desirable additional goal of therapy.