Use of calcium antagonists as monotherapy in the management of hypertension

The renin system and atrial natriuretic hormone in congestive heart failure

The renin angiotensin system is activated in the majority of patients with chronic congestive heart failure of moderate to severe symptomatology. Renin release may result from one of several different stimuli: renal tubular sodium delivery and sensing by the macula densa, sympathetic nervous system activity, and baroreceptor to changes in renal blood flow. Difficulties arise with an analysis of renin angiotensin system activity due to the necessity for diuretic therapy in the majority of these patients. Despite the presence of diuretic therapy, however, there is a wide range of renin angiotensin system activity. In evaluating this activity the administration of a converting enzyme inhibitor will block the contribution of angiotensin mediated vasoconstriction, thereby confirming the importance of the renin angiotensin system activity as a mediator of the long-term consequences of heart failure. In situations of low plasma renin activity, vasoconstriction is mediated by an alternate mechanism. The mechanisms of this non-renin mediated vasoconstriction are less apparent, but may include calcium mediated vasoconstriction, and the effects of increased cytosolic content. This low renin group of patients appear to be very sensitive to reversal of vasoconstriction by calcium channel antagonists, especially when converting enzyme inhibitors are ineffective. In an analysis of the factors that may result in renin release, tubular delivery of sodium to the macula densa may emerge as the most important regulator of renin release.(ABSTRACT TRUNCATED AT 250 WORDS)

Drug-gene interaction between the insertion/deletion polymorphism of the angiotensin-converting enzyme gene and antihypertensive therapy

BACKGROUND

Despite the availability of a variety of effective drugs, inadequate control of blood pressure is common. There are some indications that the angiotensin-converting enzyme (ACE) gene modifies the response to antihypertensive drugs, but the results have been inconclusive.

OBJECTIVE

To investigate whether the insertion/deletion polymorphism of the ACE gene modifies blood pressure differences among subjects using diuretics, beta-blockers, calcium-channel antagonists, or ACE inhibitors.

METHODS

Data were used from the Rotterdam Study, a population-based, prospective, cohort study in the Netherlands, which started in 1990 and included 7983 subjects aged 55 years or older. Data from 3 subsequent cross-sectional investigations were used, as well. Subjects were included if they had high blood pressure during one or more examinations and/or used monotherapy with a diuretic, beta-blocker, calcium-channel antagonist, or ACE inhibitor. A marginal, generalized, linear model was used to assess the association between the mean difference in systolic/diastolic blood pressure and antihypertensive classes stratified by the 3 genotypes.

RESULTS

In total, 3025 hypertensive individuals were included, and 6500 measurements of blood pressure were taken. The percentages of DD, ID, and II genotypes were 28.3%, 51.4%, and 20.3%, respectively. The mean differences in systolic blood pressure between the II and DD genotypes were 0.23 mm Hg (95% CI -5.48 to 5.94) for diuretics, -2.41 mm Hg (95% CI -6.72 to 1.90) for beta-blockers, 2.12 mm Hg (95% CI -4.64 to 8.89) for calcium-channel antagonists, and -2.01 mm Hg (95% CI -9.82 to 5.79) for ACE inhibitors.

CONCLUSIONS

The adjusted mean difference in diastolic and systolic blood pressure among diuretic, beta-blocker, calcium-channel antagonist, or ACE inhibitor users was not modified by the ACE insertion/deletion polymorphism.

Trends in medication choices for hypertension in the elderly. The decline of the thiazides

We studied the evolution in choice of antihypertensive therapy in the elderly over a seven-year period and defined factors associated with such prescribing. To accomplish this, we performed a retrospective analysis of 8428 enrollees older than 65 years of age in the New Jersey Medicaid and Medicare programs newly begun on antihypertensive therapy between 1982 and 1988. Diuretics were the most common agents prescribed (51%), followed by calcium channel blockers (14%), beta-blockers (13%), central adrenergic antagonists (11%), and angiotensin-converting enzyme inhibitors (5%). However, the use of diuretics declined sharply during the latter part of the time interval studied. Using logistic regression modeling, we determined that the odds of a subject being started on a diuretic compared with any other antihypertensive drug decreased from 1.0 during the referent years 1982 to 1984 to 0.75 in 1985 to 1986 and to 0.41 in 1987 to 1988, after controlling for demographics, comorbidity, and hospital and physician visits (P < .001). The relative odds of diuretic use were significantly increased (P < .05) for the oldest subjects (odds ratio, 1.28 for age 85 and older versus ages 65 to 74 odds), women (odds ratio, 1.15), and blacks (odds ratio, 1.14). Despite the growing evidence during the study interval of the efficacy of diuretics in treating hypertension in the elderly, diuretic use diminished throughout this period in relation to other antihypertensive drugs. Subject characteristics (oldest subjects, women, and blacks) were important determinants of physicians' choice of antihypertensive therapy.

Comparative pharmacokinetic and clinical profiles of angiotensin-converting enzyme inhibitors and calcium antagonists in systemic hypertension

Angiotensin-converting enzyme (ACE) inhibitors and calcium antagonists are important classes of antihypertensive agents. Within their respective classes, ACE inhibitors and calcium antagonists share common pharmacokinetic properties, but in contrast to ACE inhibitors, some calcium antagonists may cause a significant increase in plasma digoxin concentrations. Clinically, both classes of agents have been shown to be safe and effective in large-scale, long-term clinical trials. ACE inhibitors appear to be very well tolerated and may be associated with fewer adverse effects than some calcium antagonists. ACE inhibitors appear to blunt diuretic-induced hypokalemia, hypercholesterolemia, hyperuricemia, and hyperglycemia. Both classes of agents can be used safely in patients with renal disease, diabetes mellitus, peripheral vascular disease, and chronic obstructive pulmonary disease. They may also be used in the elderly. While ACE inhibitors are particularly useful in hypertension accompanied by congestive heart failure, calcium antagonists can be very useful when angina pectoris is present in the hypertensive patient.

Hemodynamic comparison of two nifedipine formulations in patients with essential hypertension

The hemodynamic and humoral effects and trough-to-peak 24-hour blood pressure responses of 2 nifedipine formulations, capsules and continuous-release once-daily formulation tablets, were evaluated in 10 patients with mild to moderate essential hypertension. Both formulations reduced mean arterial pressure similarly from 120 +/- 3 (baseline) to 107 +/- 2 (p less than 0.005) and 105 +/- 2 mm Hg (p less than 0.005) and total peripheral resistance index from 65 +/- 9 (baseline) to 47 +/- 4 (p less than 0.05) and 45 +/- 3 U/m2 (p less than 0.05), respectively. Renal, splanchnic and total forearm (including skin and skeletal muscle) blood flows were maintained or even increased slightly associated with reductions in regional vascular resistances. Decreases in renal, total forearm and skeletal muscle resistances were significant (p less than 0.05) with the capsules, but the decrease was only significant in renal resistance with the long-acting tablets. Intravascular volume did not expand with reduction in arterial pressure. This antihypertensive effect was not related to baseline plasma renin activity levels or age. Nifedipine tablets provided a better control of mean arterial pressure (66%) than did capsules (44%).

Comparison of once daily atenolol, nitrendipine and their combination in mild to moderate essential hypertension

1. The aim of the study was to compare the efficacy and the tolerability of treatment with atenolol (50-100 mg once daily), nitrendipine (20-40 mg once daily) and their combination (atenolol 50 mg + nitrendipine 20 mg) once daily in patients with mild to moderate essential hypertension. 2. The study was a randomised, double-blind, placebo controlled parallel groups design: blood pressures were measured at 'trough' effect (i.e. 24 h after dosing) to assess the adequacy of once-daily treatment. 3. Mean blood pressures (mm Hg) recorded on four occasions over 12 weeks of treatment were significantly lower both with atenolol (155/97 sitting: 155/104 standing) and with the combination of atenolol plus nitrendipine (153/96 sitting: 152/104 standing) than with placebo (169/108 sitting: 169/114 standing). Nitrendipine alone had no significant effect on blood pressure 24 h after dosing (165/104 sitting: 165/110 standing). 4. Withdrawals due to adverse effects were more common during treatment with nitrendipine: 7/32 of the patients experienced adverse effects attributable to intense systemic vasodilatation (e.g., flushing, erythema, headache). 2/37 patients taking atenolol were withdrawn: one because he developed a psoriatic rash and the other because of impaired peripheral circulation. Of the 35 patients taking combination treatment, two were withdrawn: one developed headaches and dyspnoea, and the other asthma. 5. The results suggest that once daily dosing with nitrendipine does not control blood pressure throughout the 24 h period in the majority of patients, and is associated with a considerable burden of adverse effects. Combination treatment was better tolerated but appeared to offer no advantages over atenolol alone in terms either of blood pressure control or adverse effects.

Cardiovascular properties of LF 2.0254, a new potent vasoselective calcium channel blocker with a slow onset of action

The effects of LF 2.0254, a new 1,4-dihydropyridine derivative, were studied in rabbit aorta stimulated by various contractile agents and in isolated guinea pig atria. LF 2.0254 inhibited in a time-dependent fashion K(+)- and CA2(+)-induced contractions of rabbit aorta with respective IC50 of 2.7 nM and 1.7 nM. An action of LF 2.0254 at the voltage operated calcium channel was consistent with the finding that LF 2.0254 antagonized 45Ca2(+)-uptake induced by depolarisation of smooth muscle, and since contractile responses evoked by (-) norepinephrine and the calcium ionophore A23187 were insensitive to the drug. In isolated paced left atria and spontaneously beating right atria of guinea pig, LF 2.0254 added for 60 min at 1 microM only slightly decreased the contractile force and beating rate. In anesthetized open-thorax dogs, LF 2.0254 (1 to 100 micrograms/kg, iv) dose-dependently lowered systemic blood pressure and increased cardiac output with a slower onset of action than nifedipine. LF 2.0254 and nifedipine decreased total peripheral, coronary, femoral and vertebral resistance. In marked contrast to nifedipine, LF 2.0254 induced only a slight decrease in left ventricular dP/dt. In conscious hypertensive dogs LF 2.0254 (0.1 and 0.3 mg/kg per os) decreased blood pressure and concomitantly increased heart rate and plasma renin activity. It is concluded that LF 2.0254 differ markedly from nifedipine in its more gradual onset of action and greater selectivity for the vasculature with respect to the myocardium.

Nicardipine monotherapy in ambulatory elderly patients with hypertension

The antihypertensive effect of nicardipine was evaluated in 89 ambulatory elderly patients with hypertension through a multicenter trial enrolling patients over the age of 65 years. After a baseline period during which they received placebo, subjects were randomized by an unbalanced assignment to a double-blind comparison of nicardipine (n = 57) and placebo (n = 32). The initial dose of nicardipine was 20 mg every 8 hours, which was then increased to 30 mg if needed. Blood pressure and heart rate were measured 1 and 8 hours after doses at each visit with subjects in both the supine and standing positions. Seventy-six per cent of patients who received nicardipine and 55% who received placebo responded (p less than 0.05). During standing, blood pressure did not decrease significantly from supine levels in either group, but a small, transient increase in heart rate occurred with nicardipine. Adverse reactions (apart from failure to respond) occurred in 8% of those who received nicardipine and 3% who received placebo. Three patients were withdrawn: two for symptoms, nausea, or flushing and one for transient and asymptomatic abnormalities on ECG. Nicardipine is effective and safe as monotherapy in elderly patients with hypertension, causing greater reduction in systolic than in diastolic pressure, but without orthostatic hypotension.

Systemic and regional hemodynamic and humoral effects of nitrendipine in essential hypertension

The hemodynamic effects of 3 months of nitrendipine therapy were evaluated in 14 patients with mild to moderate essential hypertension. Nitrendipine reduced systolic and diastolic pressures from 145 +/- 4/95 +/- 3 to 119 +/- 3/78 +/- 2 mm Hg, respectively, (p less than 0.001) through a fall in total peripheral resistance index (46 +/- 4 to 34 +/- 3 units/m2, p less than 0.001) without associated reflex cardiac stimulation. This antihypertensive effect was related directly to the height of pretreatment arterial pressure (r = -0.67, p = 0.006) but not to age or pretreatment plasma renin activity. Renal and forearm blood flow increased, vascular resistance decreased, and glomerular filtration rate remained stable. In addition, nitrendipine reduced left ventricular mass index (133 +/- 7 to 116 +/- 5 g/m2, p = 0.003) and wall thickness, changes that were accompanied by improvement in diastolic as well as systolic (ejection fraction and fractional fiber shortening rate) left ventricular functions. Intravascular volume did not expand with reduction in pressure. This study provides new information concerning the long-term hemodynamic effects and associated echocardiographic changes with nitrendipine. It also provides the first regional hemodynamic data in essential hypertensive patients detailing forearm and splanchnic changes and renal blood flow increase during prolonged treatment.

Acute and chronic studies of diltiazem in elderly versus young hypertensive patients

The pharmacodynamics, disposition and hormonal responses to acute intravenous and chronic oral diltiazem treatment were compared in young and elderly hypertensive patients. In elderly patients, supine diastolic blood pressure decreased significantly during the first week of treatment (baseline mean +/- standard error of the mean, 100 +/- 1 to 93 +/- 2 mm Hg) and decreased further during the study to 86 +/- 2 mm Hg at the end of the study. Diastolic blood pressure of the young patients decreased significantly by the third week of treatment (from 104 +/- 2 to 97 +/- 3 mm Hg) and decreased further during the study to 94 +/- 2 mm Hg at the end of the study. Baseline supine systolic blood pressure was greater in elderly than in young patients (167 +/- 5 vs 144 +/- 3 mm Hg; p less than 0.01) and was significantly reduced in the elderly by the fourth week (167 +/- 5 to 154 +/- 3 mm Hg; p less than 0.003), with a significantly reduction sustained throughout the 14-week period. Young patients had little change in systolic blood pressure. Supine heart rate tended to decrease in both groups during the 14-week period. Acute intravenous diltiazem pharmacokinetics determined at the beginning of the study showed that total diltiazem clearance was similar in elderly (13.3 +/- 1.0 ml/min/kg) and young (13.7 +/- 1.9 ml/min/kg) patients as was volume of distribution (4.2 +/- 0.3 vs 4.3 +/- 0.6 liters/kg) and elimination half-life (3.78 +/- 0.19 vs 3.69 +/- 0.23 hours).(ABSTRACT TRUNCATED AT 250 WORDS)

Systemic and pulmonary hemodynamic responses to nicardipine during graded ergometric exercise in patients with moderate to severe essential hypertension

In 10 patients with moderate to severe hypertension, the hemodynamic effects of ergometric exercise and nicardipine, a dihydropyridine calcium channel antagonist, were characterized under basal conditions and after 1 week of therapy. The responses of plasma renin activity and catecholamines were also assessed. Nicardipine induced significant reductions of systolic, diastolic and mean blood pressure under conditions of rest and peak exercise (p less than 0.001), mediated by reversal of vasoconstriction (p less than 0.001). Overall, cardiac index and stroke volume index responses were not significantly altered by nicardipine. Although rest pulmonary wedge pressure was unchanged (6 +/- 3 to 5 +/- 4 mm Hg), peak exercise pulmonary wedge pressure decreased from 24 +/- 22 to 7 +/- 5 mm Hg (p less than 0.001) with nicardipine therapy. This effect of nicardipine on pulmonary wedge pressure was present across all work loads studied, and was accompanied by reduction of peak exercise pulmonary artery pressure from 43 +/- 10 to 25 +/- 7 mm Hg (p less than 0.001). Oxygen consumption was unchanged, associated with reduction of arteriovenous oxygen difference (p less than 0.02). Both plasma renin activity (p less than 0.05) and norepinephrine (p less than 0.005) were significantly increased with nicardipine therapy. Thus, nicardipine produced significant blood pressure reduction by reversal of vasoconstriction in patients with essential hypertension. The preservation of cardiac output, with markedly reduced pulmonary wedge pressure, indicated that nicardipine improved ventricular performance in response to reversal of vasoconstriction.

Disparate hemodynamic responses to mental challenge after antihypertensive therapy with beta blockers and calcium entry blockers

The hemodynamic response to mental challenge was studied in 40 male outpatients with mild essential hypertension. The patients were treated randomly either with a beta adrenoreceptor blocker (oxprenolol) or with a calcium entry blocker (nitrendipine). Cardiovascular reactivity was evaluated with two different mental arithmetic tasks before and six months after treatment by continuously measuring systolic and diastolic pressure (ultrasonic Doppler device), heart rate (electrocardiography), and stoke volume (impedance cardiography). Patients in both treatment groups had equal decreases in arterial pressure and the same pressures at rest. In patients receiving calcium entry blockers, mental challenge provoked an increase in stroke volume and a decrease in total peripheral resistance similar to results in the pretreatment phase. In contrast, beta adrenoreceptor blockade reversed the hemodynamic response pattern to a distinct decrease in stroke volume (p less than or equal to 0.05) and an increase in total peripheral resistance (p less than or equal to 0.05). In addition, an attenuated heart rate response (p less than or equal to 0.01) and a larger increase in diastolic pressure (p less than or equal to 0.01) were found in the beta blocker group compared with the calcium entry blocker group. Although beta blockers and calcium blockers produce equal decreases in arterial pressure, beta blockers evoke an abnormal hemodynamic response to mental challenge, whereas calcium entry blockers preserve the physiologic reactivity pattern of the untreated state.

Tiapamil and hydrochlorothiazide: a double-blind comparison of two antihypertensive agents

Tiapamil is an investigational calcium-channel antagonist that is chemically related to verapamil. The antihypertensive efficacies of tiapamil and hydrochlorothiazide (HCTZ) were compared in a randomized double-blind trial. Thirty patients, age 44 to 80 years, with mild to moderate hypertension (World Health Organization stage I-II) entered and completed the study. Previous therapy, if any, was stopped for at least one week prior to study initiation, and patients received placebo tablets for two weeks. The participants were then given active medication, which was titrated for the next three weeks; HCTZ 25 to 50 mg bid or tiapamil 300 to 600 mg bid was given until supine diastolic blood pressure (BP) was no higher than 90 mm Hg or the ceiling dose was reached. Both drugs caused a significant reduction in systolic as well as in diastolic blood pressure (P less than .01). The reduction was seen in both the supine and erect position. The median decrease in supine systolic blood pressure from baseline to the end of treatment was 20 mm Hg in the tiapamil group and 27 mm Hg in the hydrochlorothiazide group, whereas the median decrease in supine diastolic blood pressure was 14 mm Hg and 18 mm Hg, respectively. The median difference in supine diastolic BP reduction after HCTZ and tiapamil administration was 3.8 mm Hg (not significant). There were no significant changes in heart rate. Dizziness occurred in one patient taking tiapamil and in three receiving HCTZ. One patient receiving HCTZ developed acute arthritis urica.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium channel blockers in the management of hypertension in the elderly

Calcium channel blockers seem to be particularly suitable for elderly hypertensive patients since these agents do not cause salt and fluid retention, postural hypotension, sedation, depression, or biochemical abnormalities. Moreover, their use is compatible with several common diseases of old age, such as diabetes, obstructive lung disease, and peripheral vascular disease. We recently conducted a study in 21 patients (average age, 79 +/- 2 years) who completed an eight-week trial with 20-mg nifedipine tablets taken twice daily. Mean blood pressure decreased from 191 +/- 2/96 +/- 2 mm Hg to 151 +/- 4/80 +/- 3 mm Hg. In 15 patients (71 percent), blood pressure decreased to less than or equal to 160/90 mm Hg; in four additional patients (19 percent), diastolic blood pressure decreased by 15 to 25 percent. Thus, there was a sustained lowering of blood pressure in 90 percent of the participants receiving nifedipine monotherapy. A review of recent studies in elderly hypertensive patients revealed similarly favorable results with calcium channel blockers given alone or in combination with other agents. The accumulating data suggest that these compounds may offer a useful new approach to the treatment of hypertension in old age. However, in these studies, the number of patients and the duration of follow-up need to be extended to confirm the favorable impression obtained thus far.

Calcium-channel blockers in acute hypertension

The acutely hypertensive patient may present with a broad spectrum of dysfunction. Given the wide variety of signs and symptoms, clinical settings, pathophysiological mechanisms, and type of end organ dysfunction, there is no ideal antihypertensive agent. In selecting an agent for treating such patients, the physician must consider efficacy in a variety of settings, rapidity of onset of action, duration of action, and ease of administration. In addition, one should keep in mind the risk of producing hypotension, the contraindication profile, the side-effect profile, and the cost and long-term usefulness of the agent. In this review, the calcium channel blockers verapamil and nifedipine are compared with drugs such as nitroprusside, diazoxide, hydralazine, labetalol, and clonidine. Verapamil, by intravenous administration, has a rapid onset of action, a reasonable duration of effect, a good side-effect profile, and appears to be useful on a long-term basis. Nifedipine, by oral or buccal administration, is useful in a variety of settings and had a rapid onset of action and reasonable duration of effect. In addition, nifedipine rarely causes hypotension, has minimal contraindications, an excellent side-effect profile, reasonable cost, and long-term utility. There is now extensive worldwide experience with verapamil and nifedipine in acute hypertension. They compare favorably with currently used agents.