clinical pharmacology ~ . '------------------------------------------------------------'

CONTROLLING CARDIAC ARRHYTHMIAS WITH ~-BLOCKERS

... Acebutolol Suppresses Premature Ventricular Contractions A positive correlation between the presence of frequent premature ventricular contractions (PYCs) and sudden cardiac death suggests that suppression of these ectopic impulses would decrease the incidence of sudden death in these patients. So far, there have been few :antiarrhythmic drugs suitable for chronic use. However, acebutolol (Ives Laboratories) effectively suppressed PYCs in a short-term study in 12 patients (II men) with frequent Pyes [I].

• In the 12 hours after a single 300mg oral dose, 9 patients showed a reduction in totalPYCs, while I showed an increase. The effect began in the first hour and was statistically significant for lQ hours(p< O.OS). From 2 hours after the dose, the concentration of the acetyl metabolite was greater than $at of acebutolol.

• In 8 of 1.1 patients who took acebutolol 300mg 8-hourly for 5-10 days PYCs were reduced by more than 70 % , and all II patients showed a reduction of at least 37 % . The reduction lasted for a whole 24-hour monitoring period. Heart rate was reduced over 24 hours from 80.5 .to 65 .5 and there was a statistically significant lengthening of the mean PR interval (p < 0.0 I), but QRS duration and QT interval (corrected for heart rate) were unchanged. Clinical toxicity was minimal, necessitating drug withdrawal in only 1 patient, and there was no laboratory or ECG evidence of toxicity .

. . . Sotalol Proves Effective Too Sotalol 20mg iy over I minute was given to 20 patients with various cardiac arrhythmias [2]. They received 1-3 infusions at 20 minute intervals. In 2 patients with sinus tachycardia, the arrhythmia was suppressed by 26 and 35 %. Paroxysmal atrial tachycardia was converted to sinus rhythm in 3 cases and was refractory to sotalol 60mg in I. Atrial flutter was converted to sinus rhythm with sotalol 20mg in I case but was resistant to 60mg and 40mg in 2 others. Premature ventricular contractions resistant to lignocaine (lidocaine) completely disappeared in 6 of 8 patients, and lignocaine-resistant ventricular tachycardia in 3 patients was converted to normal sinus rhythm. Sotalol did not change BP in normotensive patients, but in 4 hypertensive patients it normalised BP. Oral sotalol 80-l60mg bid suppressed arrhythmias in 8 of 10 patients. The other 2 discontinued because of severe sinus bradycardia in I and cardiac arrest in the other.

'Although the total number of cases studied is too small to make a definitive con­clusions (sic), the excellence of the results obtained in the treatment of acute ventriCllll!r arrhythmias associated with myocardial infarction and resistant to lidocaine .. '. is worthy of comment:

[I) Gradman. A.H. et al. : Circulation 55: 785 (May 1977) [2] Latour. Y. et al.: International Journal of Clinical Pharmacology 15: 275 (Jun 1977)

INPHARMA 6th August. 1977 p13