Calcium antagonists and the second drug for hypertensive therapy

Plasma Renin test-guided drug treatment algorithm for correcting patients with treated but uncontrolled hypertension: a randomized controlled trial

BACKGROUND

Undefined pathophysiologic mechanisms likely contribute to unsuccessful antihypertensive drug therapy. The renin test-guided therapeutic (RTGT) algorithm is based on the concept that, irrespective of current drug treatments, subnormal plasma renin activity (PRA) (<0.65 ng/ml/h) indicates sodium-volume excess "V" hypertension, whereas values >or=0.65 indicate renin-angiotensin vasoconstriction excess "R" hypertension.

METHODS

The RTGT algorithm was applied to treated, uncontrolled hypertensives and compared to clinical hypertension specialists' care (CHSC) without access to PRA. RTGT protocol: "V" patients received natriuretic anti-"V" drugs (diuretics, spironolactone, calcium antagonists, or alpha(1)-blockers) while withdrawing antirenin "R" drugs (converting enzyme inhibitors, angiotensin receptor antagonists, or beta-blockers). Converse strategies were applied to "R" patients. Eighty-four ambulatory hypertensives were randomized and 77 qualified for the intention-to-treat analysis including 38 in RTGT (63.9 +/- 1.8 years; baseline blood pressure (BP) 157.0 +/- 2.6/87.1 +/- 2.0 mm Hg; PRA 5.8 +/- 1.6; 3.1 +/- 0.3 antihypertensive drugs) and 39 in CHSC (58.0 +/- 2.0 years; BP 153.6 +/- 2.3/91.9 +/- 2.0; PRA 4.6 +/- 1.1; 2.7 +/- 0.2 drugs).

RESULTS

BP was controlled in 28/38 (74% (RTGT)) vs. 23/39 (59% (CHSC)), P = 0.17, falling to 127.9 +/- 2.3/73.1 +/- 1.8 vs. 134.0 +/- 2.8/79.8 +/- 1.9 mm Hg, respectively. Systolic BP (SBP) fell more with RTGT (-29.1 +/- 3.2 vs. -19.2 +/- 3.2 mm Hg, P = 0.03), whereas diastolic BP (DBP) declined similarly (P = 0.32). Although final antihypertensive drug numbers were similar (3.1 +/- 0.2 (RTGT) vs. 3.0 +/- 0.3 (CHSC), P = 0.73) in "V" patients, 60% (RTGT) vs. 11% (CHSC) of "R" drugs were withdrawn and BP medications were reduced (-0.5 +/- 0.3 vs. +0.7 +/- 0.3, P = 0.01).

CONCLUSIONS

In treated but uncontrolled hypertension, RTGT improves control and lowers BP equally well or better than CHSC, indicating that RTGT provides a reasonable strategy for correcting treated but uncontrolled hypertension.

Evaluation of amlodipine, lisinopril, and a combination in the treatment of essential hypertension

Angiotensin converting enzyme (ACE) inhibitors and dihydropyridine calcium antagonists are well established and widely used as monotherapy in patients with mild to moderate essential hypertension. Earlier studies combining short acting drugs from these classes require multiple dosing and were associated with poor compliance. Availability of longer acting compounds allows once daily administration to avoid the inconvenience of a multiple daily dose. It was decided to perform a randomised double blind, crossover study with the long acting calcium channel blocker amlodipine and the long acting ACE inhibitor lisinopril, given either alone or in combination in essential hypertension. Twenty four patients with diastolic blood pressure (DBP) between 95 and 104 mm Hg received amlodipine 2.5 mg and 5 mg, lisinopril 5 mg and 10 mg, and their combination as per a prior randomisation schedule. Supine and standing blood pressure and heart rate were recorded at weekly intervals. Higher doses of both the drugs individually or in combination were used if the target supine DBP below 90 mm Hg was not achieved. There was a significant additional blood pressure lowering effect with the combination when compared either with amlodipine or lisinopril alone. Five mg amlodipine and 10 mg lisinopril monotherapy achieved the target blood pressure in 71% and 72% patients respectively. The combination of 2.5 mg amlodipine with 5 mg lisinopril produced a much more significant lowering of blood pressure in a higher percentage of patients than that with an individual low dose.

Evaluation of enalapril combined with diltiazem ER in patients with stage 3-4 essential hypertension

Enalapril combined with an extended-release formulation of diltiazem was evaluated in a 12-week multicenter trial of 112 patients with Stages 3-4 essential hypertension. Patients were randomized to once daily therapy with enalapril 5 mg plus diltiazem ER 120 mg or 180 mg. Dosages could be titrated and other antihypertensive agents added for blood pressure control. Efficacy was assessed with sitting blood pressures at trough (24 hours postdose). Overall, there was a decrease of -21.7/-18.4 mmHg. Patients responding to enalapril/diltiazem ER alone had a reduction of -15.0/-16.3 mmHg. Of all patients, 70% achieved a trough sitting diastolic blood pressure of < 95 mmHg. Common drug-related adverse experiences were headache, dizziness, rash, and asthenia/fatigue. This once daily fixed-combination of enalapril/diltiazem ER was generally well tolerated and effective when given alone or with other antihypertensives in Stage 3-4 hypertension.

A comparative assessment of the duration of action of amlodipine and nifedipine GITS in normotensive subjects

1 This study in normotensive subjects compared the duration and consistency of action of amlodipine (5 mg) and nifedipine GITS (60 mg) by assessment of the attenuation of pressor responses to noradrenaline and angiotensin II. 2 Both drugs significantly attenuated pressor responses to both vasoconstrictors at 6 and 24 h post-dose with rightward shifts of up to 2.3-fold in the dose-response curves. 3 There was significantly less pharmacokinetic variability with amlodipine: for example, intra-subject variability was 33% with amlodipine and 59% with nifedipine GITS. 4 There were no significant differences in the pressor dose ratios up to 48 h post-dose with amlodipine whereas there was a significant and progressive reduction in the pressor dose ratios with nifedipine. 5 These results suggest that both drugs are broadly comparable as once daily treatments but amlodipine displayed less intra- and inter-subject variability and provided a significantly more sustained effect with a reserve of pharmacological activity up to 48 h post-dose.

The antihypertensive efficacy and tolerability of a low dose combination of ramipril and felodipine ER in mild to moderate essential hypertension

1. The antihypertensive efficacy and tolerability of a low dose combination of the angiotensin converting enzyme inhibitor ramipril (2.5 mg) and the extended release formulation of the dihydropyridine calcium channel antagonist felodipine (5 mg) were assessed in a double-blind, double dummy placebo controlled, randomised, crossover study in 20 patients (mean age 55.4 years; range 46-69) with uncomplicated mild to moderate hypertension (supine diastolic > 90 mmHg < 115 mmHg after 4 weeks of single-blind wash-out on placebo). The four randomised, double-blind, crossover study phases evaluated the response to 4 weeks of once daily treatment with placebo, monotherapy with each drug and the combination. Noninvasive ambulatory blood pressure monitoring (Spacelabs 90207) was performed for 24 h at the end of each phase. 2. The mean 24 h ambulatory blood pressure (mmHg) was 147.9/92.0 following placebo, 141.3/87.8 following monotherapy with ramipril 2.5 mg, 136.8/85.8 following monotherapy with felodipine ER 5 mg and 131.1/82.6 following the combination of ramipril 2.5 mg and felodipine ER 5 mg. All active treatment phases significantly reduced mean 24 h ambulatory diastolic pressure by comparison with placebo. The antihypertensive efficacy of the combination was additive. 3. The coadministration of ramipril did not attenuate the incidence of headache attributable to felodipine ER.

The nifedipine gastrointestinal therapeutic system in the treatment of hypertension

As the number of antihypertensive agents increases, the choice of optimal therapy becomes more difficult. Certainly, hemodynamic derangements caused by the disease state as well as therapy must be considered. Patient convenience and quality of life are also issues that must be addressed. Preliminary experience suggests that the gastrointestinal therapeutic system (GITS) push-pull osmotic pump formulation of nifedipine is safe and efficacious in the treatment of hypertension. In 1 study, nifedipine GITS was compared with sustained-release propranolol in patients with mild to moderate hypertension already receiving diuretics. Using a 2-week placebo run-in, double-blind study design, patients were randomly assigned to receive nifedipine GITS (n = 31) in doses of 30, 60 or 90 mg once daily, or sustained-release propranolol (n = 32) in doses of 80, 160 or 240 mg once daily. Previous diuretic therapy was continued. Sitting and 5-minute standing blood pressure and heart rate measurements were obtained 24 hours after dosing. At the end point of treatment, both nifedipine GITS and sustained-release propranolol reduced blood pressure compared with placebo (p less than 0.001) in the sitting and standing positions. Nifedipine GITS was more effective than sustained-release propranolol in reducing standing (p less than 0.005) and sitting (p less than 0.001) systolic blood pressure and sitting diastolic blood pressure (p less than 0.02). Sustained-release propranolol caused a greater reduction in standing (p less than 0.001) and sitting (p less than 0.0006) resting heart rate than nifedipine GITS. Both drugs were well tolerated.(ABSTRACT TRUNCATED AT 250 WORDS)

Verapamil. An updated review of its pharmacodynamic and pharmacokinetic properties, and therapeutic use in hypertension

Although verapamil is a well-established treatment for angina, cardiac arrhythmias and cardiomyopathies, this review reflects current interest in calcium antagonists as anti-hypertensive agents by focusing on the role of verapamil in hypertension. Verapamil is a phenylalkylamine derivative which antagonises calcium influx through the slow channels of vascular smooth muscle and cardiac cell membranes. By reducing intracellular free calcium concentrations, verapamil causes coronary and peripheral vasodilation and depresses myocardial contractility and electrical activity in the atrioventricular and sinoatrial nodes. Verapamil is well suited for the management of essential hypertension since it produces generalised systemic vasodilation resulting in a marked reduction in systemic vascular resistance and, consequently, blood pressure. Evidence from clinical studies supports the role of oral verapamil as an effective and well-tolerated first-line treatment for the management of patients with mild to moderate essential hypertension. Clinical studies have shown that verapamil is more effective the higher the pretreatment blood pressure and some authors have found a more pronounced antihypertensive effect in older patients or in patients with low plasma renin activity. Sustained release verapamil formulations are available for oral administration which, as a single daily dose, are as effective in lowering blood pressure over 24 hours as equivalent doses of conventional verapamil formulations given 3 times daily. As a first-line antihypertensive agent, oral verapamil is equivalent to several other calcium antagonists, beta-blockers, diuretics, angiotensin-converting enzyme (ACE) inhibitors and other vasodilators, and is not associated with many of the common adverse effects of these treatments. Verapamil may be preferred as an alternative first-line antihypertensive treatment to diuretics in elderly patients because it has similar efficacy in these patients without causing the adverse effects commonly linked with diuretic treatment. Furthermore, because verapamil does not cause bronchoconstriction, it may be used in preference to beta-blockers in patients with asthma or chronic obstructive airway disease. Reflex tachycardia, orthostatic hypotension or development of tolerance is not evident following verapamil administration. As a second- or third-line treatment for patients refractory to established antihypertensive regimens, verapamil produces marked blood pressure reductions when combined with diuretics and/or ACE inhibitors, beta-blockers and vasodilators such as prazosin.(ABSTRACT TRUNCATED AT 400 WORDS)

Issues, goals, and guidelines in selecting first-line drug therapy for hypertension

Modern antihypertensive therapy is enriched by an explosion in drug development that makes available increasingly specific agents whose effects have advanced our understanding of pressor mechanisms. This and other research into hypertensive mechanisms has defined the clinical, pharmacological, and endocrinologic heterogeneity of human hypertension. The sum of these developments is a greatly enhanced ability to identify curable and definable causes of hypertension and to pathophysiologically stratify the remaining cases of essential hypertension. Modern treatment can be much more specific than before. When long-term drug therapy is indicated, the regimen is more likely to achieve a primary goal for each patient, that is, the fewest possible drugs in the smallest amount and in lowest frequency. Two clinically quantifiable mechanisms for long-term arteriolar vasoconstriction can be identified within the spectrum of human hypertension. The first, renin-mediated vasoconstriction, is directly related to the plasma renin level. The second, sodium-volume-related vasoconstriction, is marked by a reciprocally subnormal renin level and involves abnormal sodium retention and calcium transport. A baseline renin-sodium profile can identify the pressure of one of these two forms of vasoconstriction and therefore is the key for the diagnosis of the two curable disorders that fully express one of the two pressor mechanisms--renovascular hypertension and primary aldosteronism. Renovascular hypertension, more common than once thought, is often cured by angioplasty. It is important to diagnose these curable forms before beginning long-term drug therapy. The renin-sodium profile, used in conjunction with serum potassium and creatinine measurements, is valuable not only in screening patients for curable forms, but also for stratifying the remainder according to the pathophysiological vasoconstrictor mechanism that underlies the hypertension. Converting enzyme inhibitors or beta-blockers are, by themselves, often effective in correcting the hypertension of high- or medium-renin patients, whereas calcium antagonists, diuretic agents, or alpha-blockers alone are most effective against the low-renin form of vasoconstriction. In the large midzone of renin values, if monotherapy fails, a rational basis for combined antirenin-antisodium volume therapies can be developed.

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.

Diltiazem and captopril alone or in combination for treatment of mild to moderate systemic hypertension

The efficacy and safety of sustained-release diltiazem, 60 to 180 mg twice daily, was compared with that of captopril, 25 to 75 mg twice daily, alone and in combination, in 132 patients with mild to moderate essential hypertension (supine diastolic blood pressure [BP] 95 to 114 mm Hg). All patients received placebo for 4 to 6 weeks, followed by randomization to diltiazem or captopril during the double-blind monotherapy phase. Either study drug was titrated over 6 weeks to achieve a goal supine diastolic BP reduction of at least 10 mm Hg and a diastolic BP of less than 90 mm Hg. Patients achieving the goal BP reduction were maintained on monotherapy for an additional 8 weeks. Patients not achieving the treatment goal after 8 weeks with either drug alone received the other drug in combination, titrated to achieve goal BP response. Both drugs lowered BP significantly and, at the doses used, diltiazem had a greater effect on diastolic BP than did captopril. The mean changes from baseline at week 8 were -10.6 and -7.3 mm Hg, respectively, (p = 0.01). Goal BP was achieved in 38% of patients taking diltiazem monotherapy and in 34% of patients taking captopril monotherapy. There were no significant differences between diltiazem and captopril in diastolic or systolic BP reductions by race or age. The addition of alternate therapy for non-goal achievers at week 8 resulted in significant reductions in diastolic and systolic BP by week 16.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium channel antagonists. Part IV: Side effects and contraindications drug interactions and combinations

With the correct selection of drug and patient, the calcium antagonists as a group can be remarkably effective at relatively low cost of serious side effects. Almost all side effects are dose related. Minor side effects include those caused by vasodilation (flushing and headaches), constipation (verapamil), and ankle edema. Serious side effects are rare and result from improper use of these agents, as when intravenous verapamil (or diltiazem) is given to patients with sinus or atrioventricular nodal depression from drugs or disease, or nifedipine to patients with aortic stenosis. The potential of a marked negative inotropic effect is usually offset by afterload reduction, especially in the case of nifedipine which actually has the most marked negative inotropic effect. Yet caution is required when even calcium antagonists, especially verapamil, are given to patients with myocardial failure unless caused by hypertensive heart disease. Drug interactions of calcium antagonists occur with other cardiovascular agents such as alpha-adrenergic blockers, beta-adrenergic blockers, digoxin, quinidine, and disopyramide. The most marked interaction with digoxin is that with verapamil, which may raise digoxin levels by over 50%. Combination therapy of calcium antagonists with beta-blockers is increasingly common, and is probably safest in the case of dihydropyridines. Other combinations being explored are those with angiotensin-converting enzyme inhibitors and diuretics.

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.

Platelet abnormalities and the pathophysiology of essential hypertension

The mechanisms whereby intracellular calcium concentration is controlled are briefly reviewed. With the current knowledge of both calcium homeostasis and the function and properties of cellular Ca2+-target proteins/signal transduction systems, a dysfunction of cellular calcium metabolism is considered in relation to the pathogenesis of hypertension. Although the enhanced peripheral vascular resistance characteristic of hypertension is ultimately a function of Ca2+ availability for smooth muscle cell contraction, the platelet possesses many parallel biochemical and physiological properties. Therefore, we have utilized the platelet as the cell-model for investigating the role of Ca2+ in hypertension disorders. An overview of Ca2+-linked platelet processes altered in essential hypertension is presented, and an attempt is made to integrate these multiple aberrations in a fundamental membrane lesion.

Multicenter comparison of the nifedipine gastrointestinal therapeutic system and long-acting propranolol in patients with mild to moderate systemic hypertension receiving diuretics. A preliminary experience

The efficacy and safety of nifedipine in a gastrointestinal therapeutic system (GITS) push-pull osmotic pump formulation was compared with long-acting propranolol in 49 patients with mild to moderate hypertension already receiving diuretics. Using a two-week placebo run-in, double-blind study design, patients were randomly assigned to receive nifedipine GITS (n = 24) in doses of 30 mg, 60 mg, or 90 mg once daily; or long-acting propranolol (n = 25) in doses of 80, 160, or 240 mg once daily. Previous diuretic therapy was continued. Sitting and five-minute standing blood pressure and heart rate measurements were made 24 hours after dosing. At the endpoint of treatment, both nifedipine GITS and sustained-release propranolol reduced blood pressure compared with placebo (p less than 0.001) in the sitting and standing positions. Nifedipine GITS was more effective in lowering standing systolic blood pressure than was propranolol (p less than 0.02). Propranolol caused a greater reduction in resting heart rate than did nifedipine GITS (p less than 0.003). Both drugs were well tolerated. Nifedipine GITS is an effective and safe once-daily drug for use in patients with hypertension who are already receiving diuretics, may be more effective than sustained-release propranolol, and may be better tolerated than conventional nifedipine capsules.