An open, multicentre study of acebutolol, given as a single daily dose, in the management of hypertension

Large-scale in silico identification of drugs exerting sex-specific effects in the heart

Background

Major differences exist between men and women in both physiology and pathophysiology. Dissecting the underlying processes and contributing mechanisms of sex differences in health and disease represents a crucial step towards precision medicine. Considering the significant differences between men and women in the response to pharmacotherapies, our aim was to develop an in silico model able to predict sex-specific drug responses in a large-scale.

Methods

For this purpose, we focused on cardiovascular effects because of their high morbidity and mortality. Our model predicted several drugs (including acebutolol and tacrine) with significant differences in the heart between men and women. To validate the sex-specific drug responses identified by our model, acebutolol was selected to lower blood pressure in spontaneous hypertensive rats (SHR), tacrine was used to assess cardiac injury in mice and metformin as control for a non-sex-specific response.

Results

As our model predicted, acebutolol exhibited a stronger decrease in heart rate and blood pressure in female than male SHRs. Tacrine lowered heart rate in male but not in female mice, induced higher plasma cTNI level and increased cardiac superoxide (DHE staining) generation in female than male mice, indicating stronger cardiac toxicity in female than male mice. To validate our model in humans, we employed two Chinese cohorts, which showed that among patients taking a beta-receptor blocker (metoprolol), women reached significantly lower diastolic blood pressure than men.

Conclusions

We conclude that our in silico model could be translated into clinical practice to predict sex-specific drug responses, thereby contributing towards a more appropriate medical care for both men and women.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1612-6) contains supplementary material, which is available to authorized users.

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 in the treatment of diabetic patients with hypertension

A double-blind, parallel group comparison study was carried out in 20 diabetic patients with mild to moderate hypertension to assess the effectiveness and tolerance of acebutolol compared with placebo. After a 4-week wash-out period on placebo, patients received either 400 mg acebutolol or placebo once daily for 12 weeks and then placebo for a further 4 weeks. The results showed that acebutolol was more effective than placebo in lowering raised blood pressure in these patients. No deterioration in diabetic control occurred during the study and no significant side-effects of the drug were observed compared with placebo. In particular, the previously described side-effects of beta-blocker therapy in diabetic patients were not observed as a clinical problem in this study.

Once-daily administration of acebutolol in treatment of hypertension

A comparison of once-daily and twice-daily regimens of treatments with a beta-adrenoceptor-blocking agent, acebutolol, was carried out in patients with mild to moderate essential hypertension. Following an initial placebo phase, all patients entered an open 9-week period during which the dose of acebutolol, given on a twice-daily basis to all patients, was titrated to reduce seated diastolic blood pressure to less than 90 mm Hg or to decrease it by at least 10 mm Hg. After a further 4-week maintenance period, patients whose blood pressure had been successfully controlled entered a 3-month double-blind study in which they were randomly divided into three groups: those receiving continuation of twice-daily treatment (n = 47); those receiving once-daily treatment (using the same total daily dose as in the earlier twice-daily phase (n = 97); and those receiving placebo twice daily (n = 48). By the end of the study, 78% of the once-daily treatment group were still under control, a result similar to that of 72% in the twice-daily treatment group. In contrast, only 39% of the placebo patients remained under control. Moreover, the blood pressure in this group was significantly higher than in the other two groups. Acebutolol is an efficacious antihypertensive agent when used on a once-daily basis.

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.

Merits of adding a beta blocker (acebutolol) to a diuretic (hydrochlorothiazide) in the treatment of hypertension

In a double-blind crossover study, the antihypertensive effect of hydrochlorothiazide alone and in combination with the beta blocker acebutolol was assessed in 18 patients suffering from mild to moderate hypertension. After a placebo period, the patients were placed on hydrochlorothiazide alone for four weeks at a dose of 50 mg daily. Acebutolol was than gradually titrated into the regimen until the optimum dose was established. The average dose was 555 mg per day, with the usual optimum dose 200 mg b.i.d. The patients then entered the crossover portion of the trial during which patients received either hydrocholorothiazide with acebutolol or hydrochlorothiazide with placebo. Each treatment period lasted six weeks. Blood pressure and heart rate were significantly lower with the combination treatment than with hydrochlorothiazide alone. At the end of each treatment period, the mean diastolic blood pressure (erect) was 90.5 mm Hg with hydrochlorothiazide-acebutolol but remained above 100 mm Hg with the diuretic alone. Neither hydrochlorothiazide nor acebutolol produced any significant changes in plasma renin activity or plasma aldosterone. There were very few side effects and no reports of bradycardia.

A multicentre study of a once daily dosage of acebutolol in the treatment of hypertension in general practice

A three-month open, multicentre trial was carried out in 2132 hypertensive patients under uncontrolled conditions in general practice, to assess the effectiveness and tolerance of acebutolol when given orally as a single morning dose, in the range of 200 to 1200 mg/day. Concomitant antihypertensive therapy was given to 702 patients. Forty-five patients, out of 1893 who were eligible for analysis, showed inadequate blood pressure control and were withdrawn from the study. There were 602 reports of side-effects of adverse reactions attributed to acebutolol in 584 patients, necessitating 120 withdrawals from the trials. The results showed that acebutolol given once daily produces a substantial and progressive reduction in blood pressure over the three months of the trial. The changes from pre-trial values of all haemodynamic assessments measured were statistically significant (p less than 0.001).

Acebutolol (400 mg) given as a single daily dose to hypertensive patients previously stabilized on 400 mg acebutolol daily in divided doses: an open multicentre study

An open multicentre trial was carried out in 13 hypertensive patients, who had responded satisfactorily to and been stabilized on treatment with 400 mg acebutolol daily in divided doses, to assess the effectiveness and tolerance of the same daily dosage given as a single morning dose. On admission, patients were changed over immediately to the new dosage regimen and continued on it for 3 months. Blood pressure and pulse rate measurements were made on the day before change over and then at the end of each month. The results indicated that once-a-day 400 mg acebutolol gave satisfactory continued control of blood pressure. Side-effects reported spontaneously by the patient, observed by the physician, and elicited in response to a questionnaire, diminished in incidence and severity in most of the patients during the trial period.