Ancillary pharmacologic properties of acebutolol: cardioselectivity, partial agonist activity, and membrane-stabilizing activity

A case of fatal acebutolol poisoning: an illustration of the potential of molecular networking

Acebutolol is a β1-selective adrenergic receptor antagonist with moderate membrane-stabilizing activity and intrinsic sympathomimetic activity; accordingly, the drug is indicated in hypertension, angina pectoris, and arrhythmia. However, acebutolol's beta-blocking properties also extend the QRS and QTc intervals, and may predispose the patient to ventricular tachydysrhythmia. Here, we report autopsy and toxicological findings on a fatal case of acebutolol self-poisoning in a 70-year-old woman. Toxicological analyses of post-mortem samples (using a liquid chromatography high-resolution mass spectrometry (LC-HR-MS) method) highlighted high concentrations of acebutolol and its metabolite diacetolol in femoral blood (92.8 mg/L and 21.2 mg/L, respectively) and other matrices (cardiac blood, urine, bile, and gastric contents). A molecular networking approach provided useful information on acebutolol's metabolism and revealed the existence of an unknown phase II metabolite of acebutolol. Molecular networking also facilitated visualization of the complex LC-HR-MS/MS datasets and the sample-to-sample comparisons that confirmed massive acebutolol intoxication by ingestion.

Influence of some beta-adrenoceptor antagonists on the anticonvulsant potency of antiepileptic drugs against audiogenic seizures in DBA/2 mice

The two enantiomers of propranolol antagonize generalized tonic-clonic seizures in DBA/2 mice with the (-)-enantiomer being about 1.5 times more potent than the (+)-enantiomer. Metoprolol was less active and atenolol was unable to affect audiogenic seizures. In combination with conventional antiepileptic drugs, both propranolol enantiomers tested in doses not affecting the occurrence of audiogenic seizures increased the anticonvulsant activity of diazepam, phenobarbital, valproate and lamotrigine and tended to increase that of carbamazepine and phenytoin. The effect was more pronounced with the (-)-enantiomer. This increase was associated with an enhancement of motor impairment, however, the therapeutic index of combined treatment of the antiepileptic drugs with both propranolol enantiomers was more favourable than the combination with saline alone. Metoprolol was also able to decrease the ED(50) values of the antiepileptic drugs, whereas atenolol showed no effects. Since neither enantiomer of propranolol significantly influenced the total and free plasma levels of the antiepileptics, pharmacokinetic interactions are not likely. In addition, (+)- and (-)-propranolol did not significantly affect the hypothermic effects of the antiepileptics tested. In conclusion, both enantiomers of propranolol and metoprolol showed an additive anticonvulsant effect when co-administered with some conventional antiepileptic drugs, most notably diazepam, phenobarbital, lamotrigine and valproate, implicating a possible therapeutic relevance of such drug combinations.

Acebutolol-induced ventricular tachycardia reversed with sodium bicarbonate

BACKGROUND

Acebutolol is a unique beta blocker that possesses cardioselectivity, partial agonist activity, and membrane stabilizing activity. Sodium bicarbonate is used to reverse the cardiotoxic effects of other drugs with membrane stabilizing activity. There have been no reported cases of acebutolol-induced ventricular dysrhythmias treated successfully with bolus sodium bicarbonate.

CASE PRESENTATION

A 48-year-old man ingested approximately 6.4 g of acebutolol with ethanol (blood ethanol 61 mmol/L). There were no other coingestants identified. One hour after presentation, the patient had a cardiac arrest with the monitor showing ventricular tachycardia. Sodium bicarbonate 50 mEq intravenous push converted the patient to sinus rhythm and the blood pressure improved to 129/90 mm Hg.

CONCLUSION

This case demonstrates a temporal relationship between bolus sodium bicarbonate administration and the termination of acebutolol-induced ventricular tachycardia.

Pharmacokinetic and pharmacodynamic properties of beta-blocking drugs influencing choice in treatment of systemic hypertension

Diuretics and beta blockers are the mainstay in treating mild and moderate systemic hypertension, but there is controversy as to which should be used first. Recent evidence of an increase in sudden death and a greater number of intolerable side effects in the diuretic-treated groups in the Multiple Risk Factor Intervention Trial in the U.S. and the Medical Research Council Trial in Great Britain has prompted some to suggest beta blockers as first-line therapy. However, beta blockers also have side effects, such as decreased ventricular function in patients with mild heart failure, increased airways resistance in those with chronic obstructive lung disease, increased plasma lipids, in particular low density lipoprotein cholesterol, and increased problems in patients with peripheral vascular disease and those with diabetes requiring insulin treatment. Many new beta-blocking drugs with different pharmacokinetic and pharmacodynamic properties allow the physician to choose the best one for each patient. beta-blocking drugs with long durations of action, high levels of bioavailability, beta 1 selectivity and intrinsic sympathomimetic activity appear most suitable for therapy. Cardioselectivity is suggested for patients with obstructive lung disease and peripheral vascular disease, and diabetic patients who take insulin. Long durations of action permit infrequent administration and recently agents with intrinsic sympathomimetic activity have been shown to have less effects on plasma lipid levels. Acebutolol also reduces ventricular arrhythmias, and may therefore be used to reduce sudden death in patients with coronary artery disease. The pharmacokinetic and pharmacodynamic properties of beta-blocking drugs can indicate the most appropriate choice for hypertensive patients.(ABSTRACT TRUNCATED AT 250 WORDS)