Calcium-channel blockers in systemic hypertension

Verapamil revisited: a transition in novel drug delivery systems and outcomes

Verapamil, the oldest calcium-channel blocker, is now being rediscovered and reevaluated in the light of new novel drug delivery systems and new evidence-based trials. Verapamil, a phenylalkylamine, is useful in the treatment of hypertension, stable angina, and narrow QRS supraventricular arrhythmias. This calcium antagonist is effective in both young and old, and both black and white hypertensive patients, and is free of metabolic side effects. Verapamil has a well-documented history as an effective antianginal agent when directly compared with a beta-blocker, and is more effective in reducing myocardial ischemia compared with amlodipine monotherapy. Because of the short half-life of verapamil, drug delivery systems are used to prolong the duration of action. Novel drug delivery systems using encapsulated beads or a modified osmotic pump have been designed to be taken at nighttime to provide maximal blood pressure reduction in the early morning hours and effective 24-hour blood pressure control, and to avoid excessive blood pressure reduction during sleep. The Verapamil in Hypertension and Atherosclerosis Study has documented equivalent effectiveness of verapamil compared with chlorthalidone, but showed superior plaque regression and reduced events in subjects with the greatest plaques with verapamil treatment. The Angina Prognosis Study in Stockholm, comparing verapamil and metoprolol for stable angina, found no difference in total cardiovascular mortality or combined cardiovascular events. Other large ongoing randomized, multicenter trials, including Controlled-Onset Verapamil Investigation of Cardiovascular Endpoints and the International Verapamil-Trandolapril Study, will expand our knowledge of the role of verapamil in the treatment of hypertension.

Management of hypertensive urgencies and emergencies

Hypertensive emergency is a condition in which there is elevation of both systolic and diastolic blood pressure with the presence of acute target organ disease. Hypertensive urgency is a condition where the blood pressure is elevated (diastolic > 120 mmHg) with the absence of acute target organ disease. Hypertensive emergencies are best managed with parenteral drugs and careful intraarterial blood pressure monitoring. Hydralazine has been widely used in treatment of hypertension in eclampsia and preeclampsia, and its safety has been demonstrated in these patients. Sodium nitroprusside (SNP) has the most reliable antihypertensive activity, which begins immediately after its administration and ends when the infusion is stopped. As with diazoxide, it should be used with caution in patients with impaired cerebral flow. SNP is the preferred drug in obtaining controlled hypotension in patients undergoing neurovascular surgery. Intravenous nitroglycerin is useful in patients prone to myocardial ischemia, but should be avoided in patients with increased intracranial pressure. Esmolol is effective in controlling both supraventricular tachyarrhythmias and severe hypertension. Its short onset of duration of action make it useful in the emergent setting, but because of its negative inotropic effect its use should be avoided in patients with low cardiac output. Verapamil should not be used in patients with preexisting conduction abnormalities. Nicardipine is a potent arteriolar vasodilator without a significant direct depressant effect on myocardium. As with other afterload reducing agents, it should not be used in patients with severe aortic stenosis. Because angiotensin-converting enzyme (ACE) inhibitors generally cause cerebral vasodilatation, enalaprilat may be particularly beneficial for patients who are at high risk of developing cerebral hypotensive episodes secondary to impaired cerebral circulation. Fenoldopam, a selective post-synaptic dopaminergic receptor (DA1) has been shown to be effective in treating severe hypertension with a lower incidence of side effects than SNP. Hypertensive urgencies can usually be managed with oral agents. Oral nifedipine, captopril, clonidine, labetalol, prazosin, and nimodipine have all been shown to be effective in these situations.

A new extended-release formulation of diltiazem HCl for the treatment of mild-to-moderate hypertension

Calcium-channel blockers are a safe and effective treatment modality and have been used extensively in the treatment of angina and hypertension. Dilacor XR capsules, a new extended-release formulation of diltiazem, has been developed for the treatment of hypertension. Dilacor XR (Rhône-Poulenc Rorer Pharmaceuticals Inc., Collegeville, PA) uses a novel drug delivery system, the Geomatrix (JAGO Research AG, Zollikon, Switzerland) controlled-release system, to deliver diltiazem at a constant rate for 24 hours. The rate of absorption is also slower. As doses of Dilacor XR were increased from 120 mg to 540 mg/day, there were disproportionate increases observed in area under the curve, maximum peak plasma concentration, minimum peak plasma concentration, and average peak plasma concentration. The efficacy data from two clinical trials have confirmed the established efficacy of diltiazem and the 24-hour efficacy of Dilacor XR in the control of mild-to-moderate hypertension. The incidence of adverse effects with Dilacor XR in doses as high as 540 mg/day was generally comparable to that of placebo. This new extended-release formulation of diltiazem should significantly facilitate blood pressure control because of better patient compliance with a once daily regimen.

Nisoldipine: a new dihydropyridine calcium-channel blocker

Nisoldipine is a new calcium-channel blocker of the dihydropyridine subclass, with a chemical structure similar to nifedipine. It has been used in clinical trials to assess its efficacy and safety in patients with hypertension, angina pectoris, and congestive heart failure. Similar to other dihydropyridines, nisoldipine is a potent peripheral and coronary dilator. The most optimal dosage regimen has not been established in clinical trials. The drug appears to have a favorable side-effect profile.

Rapid-acting parenteral antihypertensive agents

Parenteral antihypertensive agents are useful in those clinical situations where rapid reduction of blood pressure is necessary or where treatment with oral antihypertensive medications is not feasible. Given the diverse selection of parenteral antihypertensive drugs now available, therapy can be individualized. The presence of concurrent diseases will often influence the decision-making process regarding choice of an agent. Complications of parenteral antihypertensive therapy can arise from the intrinsic properties of the various drugs or the development of severe hypotension. Gradual lowering of blood pressure, in conjunction with careful clinical evaluation, will minimize the risks of acute parenteral antihypertensive therapy. Given that parenteral antihypertensive therapy often needs to be replaced by oral therapy, those drugs that can be used both parenterally and orally may have an advantage.

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)

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.

Efficacy and safety of sustained-release diltiazem as replacement therapy for beta blockers and diuretics for stable angina pectoris and coexisting essential hypertension: a multicenter trial

To determine if a sustained-release form of the calcium entry blocker diltiazem would be a satisfactory substitute for the combination of beta-adrenergic blocking agent and thiazide diuretic in the treatment of systemic hypertension and angina pectoris, 38 patients were studied in a 4-center trial. Blood pressure and heart rate were measured in the supine position, immediately after and 5 minutes after standing. Modified Bruce protocol treadmill tests were performed to determine the time to onset of 1 mm ST-segment depression, time to onset of chest pain and time to termination of exercise. Diltiazem monotherapy resulted in equivalent blood pressure control in 28 of 38 patients (74%). In the remaining patients, blood pressure control was achieved with resumption of the diuretic. Blood pressure with beta blocker plus diuretic compared with diltiazem were, in the supine position 137 +/- 22/82 +/- 7 (+/- 1 standard deviation) versus 139 +/- 22/82 +/- 8 mm Hg, immediately after standing 131 +/- 20/84 +/- 9 versus 133 +/- 21/82 +/- 10 mm Hg and after standing for 5 minutes 134 +/- 19/85 +/- 8 versus 137 +/- 18/85 +/- 9 mm Hg (difference not significant for each). The heart rate with diltiazem was higher supine (67 +/- 11 versus 60 +/- 11 beats/min), standing (73 +/- 13 versus 64 +/- 14 beats/min) and 5 minutes after standing (73 +/- 14 versus 63 +/- 14 beats/min, p less than 0.01 for each).(ABSTRACT TRUNCATED AT 250 WORDS)