Acebutolol (Acebutolol Hydrochloride) - Drug Interactions, Contraindications, Overdosage

DRUG INTERACTIONS

Carcinogenesis, Mutagenesis, Impairment of Fertility

Chronic oral toxicity studies in rats and mice, employing dose levels as high as 300 mg/kg/day, which is equivalent to 15 times the maximum recommended (60 kg) human dose, did not indicate a carcinogenic potential for acebutolol. Diacetolol, the major metabolite of acebutolol in man, was without carcinogenic potential in rats when tested at doses as high as 1800 mg/kg/day. Acebutolol and diacetolol were also shown to be devoid of mutagenic potential in the Ames Test. Acebutolol, administered orally to two generations of male and female rats at doses of up to 240 mg/kg/day (equivalent to 12 times the maximum recommended therapeutic dose in a 60-kg human) and diacetolol, administered to two generations of male and female rats at doses of up to 1000 mg/kg/day, had no significant impact on reproductive performance or fertility.

Pregnancy

Teratogenic Effects

Pregnancy Category B

Reproduction studies have been performed with acebutolol in rats (up to 630 mg/kg/day) and rabbits (up to 135 mg/kg/day). These doses are equivalent to approximately 31.5 and 6.8 times the maximum recommended therapeutic dose in a 60-kg human, respectively. The compound was not teratogenic in either species. In the rabbit, however, doses of 135 mg/kg/day caused slight fetal growth retardation; this effect was considered to be a result of maternal toxicity, as evidenced by reduced food intake, a lowered rate of body weight gain, and mortality. Studies have also been performed in these species with diacetolol (at doses of up to 450 mg/kg/day in rabbits and up to 1800 mg/kg/day in rats). Other than a significant elevation in postimplantation loss with 450 mg/kg/day diacetolol, a level at which food consumption and body weight gain were reduced in rabbit dams and a nonstatistically significant increase in incidence of bilateral cataract in rat fetuses from dams treated with 1800 mg/kg/day diacetolol, there was no evidence of harm to the fetus. There are no adequate and well-controlled trials in pregnant women. Because animal teratology studies are not always predictive of the human response, acebutolol should be used during pregnancy only if the potential benefit justifies the risk to the fetus.

OVERDOSAGE

No specific information on emergency treatment of overdosage is available for acebutolol. However, overdosage with other beta-blocking agents has been accompanied by extreme bradycardia, advanced atrioventricular block, intraventricular conduction defects, hypotension, severe congestive heart failure, seizures, and in susceptible patients, bronchospasm and hypoglycemia. Although specific information on the emergency treatment of acebutolol overdose is not available, on the basis of the pharmacological actions and the observations in treating overdoses with other beta-blockers, the following general measures should be considered:

1. Empty stomach by emesis or lavage.
2. Bradycardia: IV atropine (1 to 3 mg in divided doses). If antivagal response is inadequate, administer isoproterenol cautiously since larger than usual doses of isoproterenol may be required.
3. Persistent hypotension in spite of correction of bradycardia: Administer vasopressor (e.g., epinephrine, norepinephrine, dopamine, or dobutamine) with frequent monitoring of blood pressure and pulse rate.
4. Bronchospasm: A theophylline derivative, such as aminophylline and/or parenteral β₂-stimulant, such as terbutaline.
5. Cardiac failure: Digitalize the patient and/or administer a diuretic. It has been reported that glucagon is useful in this situation.

Acebutolol is dialyzable.

CONTRAINDICATIONS

Acebutolol hydrochloride capsules are contraindicated in: 1) persistently severe bradycardia; 2) second- and third-degree heart block; 3) overt cardiac failure; and 4) cardiogenic shock (see WARNINGS).