Reduction of ventricular ectopic beats with oral acebutolol: a double-blind, randomized crossover study

Acebutolol: Ventricular Tachycardia

This Hospital Pharmacy feature is extracted from Off-Label Drug Facts, a quarterly publication available from Wolters Kluwer Health. Off-Label Drug Facts is a practitioner-oriented resource for information about specific drug uses that are unapproved by the US Food and Drug Administration. This new guide to the literature enables the health care professional or clinician to quickly identify published studies on off-label uses and determine if a specific use is rational in a patient care scenario. A summary of the most relevant data is provided, including background, study design, patient population, dosage information, therapy duration, results, safety, and therapeutic considerations. References direct the reader to the full literature for more comprehensive information before patient care decisions are made. Direct questions or comments regarding Off-Label Drug Uses to hospital pharmacy@drugfacts.com .

Holter-guided identification of premature ventricular contractions susceptible to suppression by beta-blockers

To evaluate whether the identification of the different types of relations between premature ventricular contractions (PVCs) and the preceding sinus cycle length is capable of predicting the effect of beta-blockers on the PVCs themselves, 55 patients (43 men, 12 women, mean age 52.6 +/- 15.6 years) with different cardiac diseases, and >30 PVCs/hr characterized by stability and the same relation at two Holter monitoring periods were studied. The relation was tachycardia enhanced (the shorter the preceding cycle length, the higher the incidence of PVCs) in 23 patients (group 1); indifferent (no correlation between the preceding cycle length and PVC incidence) in 21 (group 2); and bradycardia enhanced (the longer the preceding cycle length, the higher the incidence of PVCs) in 11 (group 3). A third Holter monitoring was performed 6 days after nadolol administration (80 mg/day) to evaluate its effect on the three types of PVCs. Incidence in all patients (-88;p<0.001). In group 2, it caused a reduction in the majority of patients (-60%;p<0.05) but an increase in five. In group 3, it caused a reduction in only half of the patients (-45%) and a 91% increase in the remainder. The difference in the effect of nadolol in the three groups was highly significant (X2=27.5;p<0.0001). The relation between the incidence of PVCs and the preceding cycle length is a useful means of identifying subsets of patients with PVCs who will benefit from beta-blockers.

The effects of slow channel blockers and beta blockers on atrioventricular nodal conduction

The PR interval on the electrocardiogram represents the time that it takes an impulse to travel through the atrium and atrioventricular (AV) conduction system to the ventricles. Normally, activation is slowest in the AV node, and variations in PR interval most commonly parallel changes in AV nodal activation time. The AV nodal conduction time and effective refractory period are rate dependent and, in adult humans, are usually prolonged with increasing atrial paced rates. In addition, alterations in autonomic tone effect AV nodal conduction as well as sinus rate. The effect is usually in the same direction but often to different degrees. In patients with normal AV nodal function, parasympathetic and sympathetic tone are balanced at rest, but in patients with abnormal AV conduction, the effect of the parasympathetic system is more marked. Drugs including the slow channel blockers and beta blockers, affect AV nodal function. Slow channel blockers inhibit the slow inward calcium current, which may prolong conduction and refractoriness in the AV node. However, whereas diltiazem and verapamil have been shown to prolong AV nodal conduction and refractoriness in humans, nifedipine, a potent vasodilator, cannot be used in doses large enough to affect the AV node. The increase in PR interval caused by verapamil is minimal, and at doses of less than 480 mg/d, AV block occurs infrequently. When AV block occurs, it is first degree block in most patients, and it is usually asymptomatic. The electrophysiologic effects of diltiazem are similar to those of verapamil. Beta blockers also have a negative dromotropic effect on the AV node. They prolong the AH interval and AV nodal refractory periods and may lengthen the PR interval. The prolonged PR interval rarely results in more than first degree AV block in patients receiving maintenance therapy. In selected patients, combination therapy with a slow channel blocker and a beta blocker rarely causes second-degree AV block.

Antihypertensive therapy and the concept of total cardiovascular protection

Drug-induced reduction of elevated blood pressure decreases cardiovascular mortality and morbidity in patients with moderate and severe hypertension. Furthermore, antihypertensive drug studies in mild hypertensive subjects (diastolic blood pressure 90 to 104 mm Hg) have shown protection against stroke, left ventricular hypertrophy, congestive heart failure and progression of renal damage, as well as improved patient longevity. The Hypertension Detection and Follow-up Program trial, recently carried out in the U.S., documented reduced coronary artery disease events (fatal and nonfatal) in special drug-treated patients with mild hypertension. From the standpoint of practical management and considering the ubiquity of essential hypertension, a modified stepped-care regimen advocating initial drug therapy with a beta blocker and addition of low-dose thiazide diuretic when necessary constitutes a judicious approach for widespread application. Although there are 8 orally active beta blockers currently approved in the U.S. for clinical use in systemic hypertension, only acebutolol possesses all of the salutary pharmacologic properties of cardioselectivity, intrinsic sympathomimetic activity and hydrophilicity, thereby making this compound an effective and safe beta-blocking agent for first-order management of a broad segment of the hypertensive population.

The role of beta blocking agents as adjunct therapy to membrane stabilizing drugs in malignant ventricular arrhythmia

Antiarrhythmic drugs are often either partially or totally ineffective for the suppression of ventricular arrhythmias in a given patient. Drug combinations afford an additional therapeutic option. We report the role of beta-blocking agents as adjunct therapy to membrane stabilizing drugs in the management of patients with malignant ventricular arrhythmias. The study group included 54 patients who were evaluated by 24-hour ambulatory monitoring and symptom-limited exercise testing. Patients underwent control studies without antiarrhythmic drugs, were evaluated on membrane stabilizing drugs and beta blocking agents separately, and were then tested on combination therapy. The combination of a beta-blocking agent and a membrane stabilizing drug abolished ventricular tachycardia and couplets in 83% and 86% of exercise tests in patients with this arrhythmia present during therapy with membrane drugs alone (p less than 0.01). The addition of a beta blocker to a membrane drug, as evaluated by ambulatory monitoring, resulted in an abolition of ventricular tachycardia and couplets in 43% and 20% of studies (p less than 0.05). Ventricular premature beat frequency was reduced by more than 50% in 65% of exercise tests and in 52% of monitoring studies (p less than 0.05). In this population, beta-blocking agents failed to reduce ventricular arrhythmias when used alone. Thus the addition of a beta blocker to a membrane stabilizing drug significantly enhances the suppression of ventricular arrhythmia, especially when assessed by exercise testing. This results from synergistic drug effects of the combination rather than from the effect of the individual drugs.

Acebutolol: a review of its pharmacology, pharmacokinetics, clinical uses, and adverse effects

Acebutolol is a new hydrophilic, cardioselective beta-adrenergic-blocking agent that possesses partial agonist and membrane-stabilizing activities. In the treatment of mild to moderate essential hypertension, once-daily acebutolol as monotherapy provides effective control in a large majority of patients and produces a further reduction in blood pressure when used concomitantly with diuretics. Acebutolol is as effective as other beta-blocking agents, and in a large, double-blind, parallel study against propranolol was found to cause less reduction in heart rate, and fewer neurologic side effects and patient withdrawals due to adverse effects. Oral acebutolol is also effective in suppressing premature ventricular contractions, and in small numbers of patients generally beneficial results were obtained in supraventricular and ventricular arrhythmias with intravenous administration. These salutary effects are attributable to beta blockade. Controlled clinical trials documented the antianginal actions of oral acebutolol in chronic stable angina pectoris; its efficacy in this regard is comparable to that of other beta-blocking agents. The drug produces smaller decreases in heart rate and cardiac output and alterations in peripheral vascular hemodynamics than beta-blocking drugs without partial agonist activity, and because of its cardioselectivity, it may be used cautiously in patients with bronchospastic disease. Acebutolol has minimal metabolic effects and does not elevate levels of blood lipids during long-term therapy; high-density-lipoprotein cholesterol increased with acebutolol in a small number of patients.

Acebutolol: ten years of experience

During 10 years of clinical use involving almost 3 million patient-years, acebutolol has become established as a remarkably safe and well-tolerated beta-blocking agent, effective in treating essential hypertension and cardiac arrhythmias. The existence of a long-lived active metabolite (diacetolol) confers a 24-hour duration of action, which permits effective use of a once-daily regimen, particularly for hypertension. Acebutolol has low lipid solubility and low protein binding; the former property reduces the risk of central side effects, and the latter means that displacement interactions with other drugs are unlikely. Because acebutolol and its metabolite normally have both renal and hepatic excretion pathways, an alternative pathway is available should either be compromised through disease. Acebutolol is cardioselective, and clinical use has borne out the low incidence of bronchospasm in patients with impaired lung function. The possession of intrinsic sympathomimetic activity (ISA) leads to only modest reductions in cardiac output, which in turn reduces the chance of excessive bradycardia and the likelihood of precipitating heart failure. A combination of selectivity and ISA may be responsible for the low incidence of tiredness and cold extremities observed with acebutolol compared with other beta blockers. The unique pharmacologic and pharmacokinetic profile of acebutolol confers several therapeutic advantages and may be responsible for the generally low level of side effects experienced in clinical use.

Comparison of acebutolol and propranolol therapy for ventricular arrhythmias

The effects of acebutolol, a new investigational cardioselective beta blocker, and propranolol on ventricular arrhythmias were compared in 14 patients with more than 30 premature ventricular contractions (PVCs) per hour. Each patient served as their own control, receiving both drugs and placebo in random sequence and in double-blind fashion, with an intervening one-week, drug-free period. Each drug was given for a two-month period, the maximum acebutolol dosage reaching 600 mg tid and the maximum propranolol dosage 80 mg tid. Seventy-two-hour ambulatory electrocardiographic monitoring assessed arrhythmia frequency for each study period. Mean PVC counts did not significantly differ during the two control periods. Acebutolol decreased mean PVC count by 65% (P less than .02), with eight patients exhibiting a 70% or greater decrease. Only three patients exhibited a similar decline with propranolol. The incidence of PVCs was not significantly decreased by propranolol. Acebutolol reduced the number of couplets by 70% (P less than .04), whereas propranolol did not significantly affect couplets. At the dosage of 600 mg tid, acebutolol was well tolerated, effectively suppressed total PVCs and couplets, and appeared to be more effective than propranolol administered at 80 mg tid.

Efficacy of flecainide in the management of ventricular arrhythmias: comparative study with amiodarone

The effects on ventricular arrhythmias of a new class IA drug, flecainide, were compared with those of amiodarone in 10 patients with frequent, chronic, and stable ventricular ectopic beats (VEBs). The study consisted of an initial 1-week, placebo-controlled, baseline period followed by two 12-day, randomized, crossover, double-blind treatment periods with incremental dosage and 1 month of placebo between drug periods. Frequent VEBs, which were present in all 10 patients during both placebo control periods (30 or more VEBs/hour every hour, during 24-hour Holter monitoring), were markedly suppressed (reduction greater than 80%) in nine patients with both drugs (p less than 0.01). There was almost total abolition of the VEBs in six patients with flecainide, and the satisfactory results with a minimal dose in three demonstrate its fast onset of action. Side effects from either agent were infrequent and no discontinuation was necessary. We conclude from our study that flecainide is a highly effective antiarrhythmic agent.

Comparison of the antiarrhythmic effects of acebutolol and propranolol in the treatment of ventricular arrhythmias

This study was designed to assess the relative antiarrhythmic activity of fixed doses of 2 beta-adrenergic blocking agents, propranolol and acebutolol, in a prospective double-blind crossover trial. Twenty-one patients who had at least 30 premature ventricular contractions (PVCs) per hour while receiving placebo were entered into the study. Ten patients were randomized to initially receive propranolol, 40 mg every 8 hours, and 11 were assigned to receive acebutolol, 300 mg every 8 hours. After 6 weeks of treatment, patients were weaned off medication for 1 week and then placed on placebo for 1 week. Eighteen patients were available and eligible for crossover to the alternative regimen for an additional 6 weeks. All 21 patients completed courses with propranolol and 17 completed courses with acebutolol. The mean number of PVCs per hour during placebo, propranolol and acebutolol treatment were 267, 87 and 119, respectively. Using paired t test statistics on observation differences, both propranolol and acebutolol significantly reduced the number of PVCs per hour compared with placebo, whereas similar analysis revealed no significant difference in the antiarrhythmic effect. However, with the current sample size the power of the test is too low for the latter conclusion to be stated with confidence. Side effects were mild and infrequent, requiring discontinuation of acebutolol in 2 patients and discontinuation of propranolol in 1. Thus, acebutolol is a safe and effective antiarrhythmic agent and compares favorably with propranolol.