Verapamil and propranolol: a comparison of two antihypertensive agents

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)

Calcium channel antagonists. Part III: Use and comparative efficacy in hypertension and supraventricular arrhythmias. Minor indications

The major antihypertensive mechanism of calcium antagonists is by decreasing the systemic vascular resistance, modified by the counter-regulatory responses of the baroreflexes and the renin-angiotensin-aldosterone system. In severe hypertension, the concept that calcium overload of the vascular myocyte could precipitate or aggravate peripheral vasoconstriction provides a logical basis for the use of these agents as first choice therapy; nifedipine, especially, has been well tested. As monotherapy for mild to moderate hypertension each of the three first-generation agents compares well with beta-blockers. Calcium antagonists may have a special role in the therapy of certain patient groups (elderly, black) or in those subjects whose life style involves intense physical or mental exertion (hemodynamics better maintained than with beta-blockade) or in patients with early end-organ damage such as left ventricular hypertrophy or renal insufficiency. However, the goal blood pressure may not be reached during monotherapy so that drug combinations may be required. Further indications for these compounds are as follows. Verapamil and diltiazem are frequently used in supraventricular tachycardias including acute and chronic atrial fibrillation. In the arrhythmias of the Wolff-Parkinson-White syndrome, there is the potential danger of provocation of anterograde conduction. Further indications for calcium antagonists, still under evaluation, include congestive heart failure (controversial), hypertrophic cardiomyopathy (verapamil), primary pulmonary hypertension (high doses required), Raynaud's phenomenon (nifedipine and diltiazem effective), peripheral vascular disease (proof not yet documented), cerebral insufficiency and subarachnoid hemorrhage (nimodipine promising), migraine, exertional bronchospasm, renal disease, atherosclerosis (experimental), and primary aldosteronism (nifedipine inhibits aldosterone release). Second-generation agents include dihydropyridines, such as nitrendipine, nicardipine, felodipine, amlodipine, nisoldipine, nimodipine, and isradipine. From these will be selected agents that are longer acting and provide higher vascular selectivity. New preparations of existing agents include slow-release formulations of nifedipine, verapamil, and diltiazem. 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 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. Yet caution is required when 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.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of sustained-release verapamil therapy on the blood pressure at rest and on the pressor response to isometric exertion in hypertensive patients

The effect of a new formulation of verapamil sustained release (SR) 240 mg tablets on resting blood pressure (BP) and on the pressor response to isometric exertion have been examined in a single-blind, placebo-controlled, cross-over study in 12 hypertensive patients (mean age 45 years). SR verapamil and placebo were administered every 12 h for 6 consecutive weeks. At the end of each period of treatment BP and heart rate (HR) were measured at rest and during isometric exercise, performed as a handgrip (HG) test for 3 min at 30% of the maximum voluntary contraction. There was a significant reduction in resting systolic and diastolic BP, with no change in HR. BP and HR at peak exercise were lower after verapamil than after placebo, but the maximal absolute increase did not change during verapamil therapy. The results are compatible with a role of SR verapamil b.d. in reducing resting BP in hypertension, and in lowering very high pressure at the peak of a HG test, without modifying the physiological reactivity of cardiovascular system.

Cardiovascular effects of verapamil in patients with essential hypertension

The cardiovascular effects of intravenous verapamil and 3 months of oral administration of a slow-release form of verapamil (verapamil-SR) were studied in 10 patients with mild-to-moderate essential hypertension. Intravenous verapamil reduced arterial pressure by 15% (p less than .01) through a fall in total peripheral resistance of 29% (p less than .01); provoked a reflexive rise in heart rate (by 19%, p less than .02), cardiac output (by 74%, p less than .01), and plasma catecholamines; and shifted intravascular volume toward the cardiopulmonary circulation indicating peripheral venoconstriction. Quite in contrast to the immediate effects of the intravenous drug, oral therapy with verapamil-SR for 2 to 3 months lowered arterial pressure effectively (by 15%, p less than .01) by inducing vasodilation of 15% (p less than .02), but without causing reflex tachycardia, activation of the sympathetic-adrenergic or renin-angiotensin systems, or volume expansion. Oral therapy with verapamil-SR preserved systemic and renal blood flow and slightly reduced cardiac mass (by 6%, p less than .05) and renal vascular resistance (by 25%, p less than .05). Whereas intravenous verapamil tended to depress myocardial contractility, oral verapamil-SR did not at all affect myocardial contractility or left ventricular function. These cardiovascular effects make verapamil-SR an excellent agent for long-term antihypertensive therapy.