The efficacy of cibenzoline in preventing PES induction of ventricular tachycardia in the dog

Effects of cibenzoline on cardiac function and metabolism in the rat heart--lung preparation

BACKGROUND AND OBJECTIVE

Although there is concern that cibenzoline, an antidysrhythmic drug for the treatment of ventricular and supraventricular dysrhythmias, may be associated with dose-dependent inhibition of myocardial contractility there are few reports about the relationship between myocardial metabolism and cardiac function when it is used. The present study was designed to investigate the effects of cibenzoline on cardiac function and metabolism. The effects of cibenzoline on cardiac function and myocardial metabolism were assessed in the isolated rat heart-lung preparation.

METHODS

Thirty-two male Wistar-ST rats were divided into four groups: control, and those to receive cibenzoline, either 300, 900 or 3000 ng mL(-1). The cibenzoline was administered into the perfusate 5 min after the start of perfusion. Heart rates in the 3000 ng mL(-1) group were significantly lower than those in the control group. Cardiac output in the 3000 ng mL(-1) group at 15 and 30 min was significantly lower than in the control group. In all groups, values for %LV dP/dt max (the ratio of values at each time to those at 5 min) at 20, 25, 30 min were significantly higher than at 5 min. Myocardial adenosine triphosphate concentration in the 3000 ng mL(-1) group was significantly lower than in controls. There was no difference between groups in the lactate/pyruvate ratio.

CONCLUSION

The therapeutic range of cibenzoline has few effects on cardiac function and metabolism, although concentrations 10 times greater may cause a deterioration in myocardial metabolism.

Cardiovascular effects of optical isomers of cibenzoline, assessed in the canine isolated, blood-perfused papillary muscle and sinoatrial node preparations

A clinically available racemic mixture of the optical isomers of cibenzoline possesses a potent sodium channel-blocking action in addition to the moderate calcium channel-blocking action. It has been reported that the S(-)-isomer inhibits sodium channels more potently than calcium channels, whereas the R(+)-isomer suppresses the sodium channels as well as calcium channels, and that the calcium channel-blocking potency of these isomers is similar. This study was designed to assess the effects of each optical isomer of cibenzoline on ventricular contraction, coronary blood flow, and sinus node automaticity by using the canine isolated, blood-perfused papillary muscle and sinoatrial node preparations. Each isomer showed negative inotropic and chronotropic effects as well as coronary vasodilator action in a dose-dependent manner. The negative inotropic effect of S(-)-cibenzoline was 1.8 times more potent than that of R(+)-cibenzoline, whereas there was no significant difference between the isomers in the negative chronotropic and coronary vasodilator effects. These results suggest that the difference of the inotropic effects between the optical isomers of cibenzoline is mainly derived from the extent of the sodium channel-blocking action, whereas the vasodilator and negative chronotropic effects may chiefly depend on the calcium channel inhibition.

Cibenzoline. A review of its pharmacological properties and therapeutic potential in arrhythmias

Cibenzoline is a class I antiarrhythmic drug with limited class III and IV activity which can be administered orally or intravenously. An elimination half-life of about 8 to 12 hours permits twice daily administration, although age and renal function must be considered when determining dosage. Cibenzoline has some activity in ventricular and supraventricular arrhythmias, including drug-refractory ventricular tachycardia or ventricular arrhythmias following recent acute myocardial infarction, although results in patients with sustained ventricular tachycardia are less promising. In comparative trials, cibenzoline has demonstrated efficacy similar to or better than that of a variety of other class I antiarrhythmic drugs and was at least as well tolerated, with a more convenient dosage schedule. However, further studies to clarify the proarrhythmic effects of cibenzoline and its use in patients with impaired left ventricular function are required, and the use of cibenzoline (and other class I antiarrhythmic agents) in patients with other than potentially lethal ventricular arrhythmias should be avoided following the results of the CAST studies. Thus, cibenzoline is an effective antiarrhythmic agent with a favourable pharmacokinetic profile that may be considered with other class I drugs in patients requiring therapy for high risk arrhythmias.

Comparison of Ca2+ channel inhibitory effects of cibenzoline with verapamil on guinea-pig heart

1. Cibenzoline, a class 1 antiarrhythmic drug, was studied on the effects upon the myocardial slow inward Ca2+ current (ICa) and the contractile force, and was compared with verapamil. 2. In voltage-clamp experiments with guinea-pig ventricular myocytes, cibenzoline caused a concentration-related inhibition of ICa (IC50 = 30 microM), whereas verapamil exerts a stronger effect (IC50 = 0.6 microM). 3. Cibenzoline also produced a concentration-related decrease in contractile force of isolated papillary muscle preparation (IC50 = 30 microM), while IC50 of verapamil was 0.8 microM. 4. Although the myocardial Ca2+ channel blocking effect of cibenzoline is about 1/50 compared to verapamil, cibenzoline possesses an inhibitory action on Ca2+ channel as well as on Na+ channel.

Evaluation of dosing interval and optimum dose of cibenzoline

Fifteen patients with ventricular premature complexes (VPCs) were included in this open study designed to assess the relative efficacy of bid (two times daily) and tid (three times daily) dosing regimens for cibenzoline as compared with qid (four times daily) administration. Patients started therapy with qid administration; this was followed in sequence by tid and bid administration at the maximum effective total daily dose determined during the qid administration. Of the nine patients evaluated for efficacy for suppression of VPCs, eight demonstrated a 75% or greater suppression of VPCs with cibenzoline administered qid (total daily dose of 130-325 mg). This effectiveness was maintained in four patients with a bid regimen and in three with a tid regimen. All four patients who had ventricular tachycardia (VT) had a decrease in the number of VT episodes while receiving cibenzoline (only one of these patients had satisfactory suppression of VPCs at the same dosage regimen). Twelve patients continued to receive extended therapy with cibenzoline for up to two years, as this was considered to be the optimum antiarrhythmic treatment for these patients. Two patients had to be removed from the study and two had the dosage lowered because of adverse reactions (dry mouth, blurred vision, dizziness, congestive heart failure) although in one instance, the congestive heart failure was subsequently considered to be unrelated to cibenzoline. One patient was able to complete the short-term phase of the trial, but was not given extended treatment because of persistent dry mouth. Two patients had treatment discontinued during the extended therapy phase because of adverse reactions (fever, nausea, vomiting, asthenia).(ABSTRACT TRUNCATED AT 250 WORDS)

Antiarrhythmic efficacy and hemodynamic effects of cibenzoline in patients with nonsustained ventricular tachycardia and left ventricular dysfunction

This was a prospective single-blind, placebo-controlled study of cibenzoline in 21 patients with five or more runs of nonsustained ventricular tachycardia (VT) and left ventricular dysfunction (mean left ventricular ejection fraction 36 +/- 24%). Ambulatory electrocardiographic monitoring revealed a baseline of 616 +/- 431 runs of VT/day on placebo. Of the 18 patients tolerating the drug, 14 (77%) patients initially had a 75% or greater reduction in VT (177 +/- 164 runs of VT/day, p less than .05). A repeat ambulatory electrocardiogram documented long-term suppression of VT in 13 of 14 patients at 1 month (2.1 +/- 1.3 runs VT/day, p less than .01), in 10 of 14 patients at 3 months (2.5 +/- 1.9 runs VT/day, p less than .01), and in nine of 14 patients at 6 months (1.5 +/- 0.8 runs VT/day, p less than .01). Aggravation of arrhythmia or drug failure was seen in four of 18 (22%) patients (new onset of sudden cardiac death, two patients; sustained VT, two patients). Hemodynamic measurements were obtained with the use of right heart catheterization in patients at rest and exercising during the placebo phase and after 60 hr of oral cibenzoline. Group hemodynamic variables, both measured and derived, showed no detrimental effect of cibenzoline. However, in three of 21 patients (mean ejection fraction 21%), cibenzoline was discontinued due to severe depression of left ventricular function. Caution is recommended in the use of cibenzoline in patients with left ventricular ejection fractions of less than 25%.

Antiarrhythmic effects of cibenzoline

Thirty-three patients with ventricular tachyarrhythmias were referred for evaluation of their arrhythmias using programmed electrical stimulation to guide antiarrhythmic therapy. Cibenzoline succinate, a new antiarrhythmic agent, was compared to procainamide in patients with ventricular tachycardia. Cibenzoline was given intravenously, initially 1.0 mg/kg, then in 1 mg/kg increments to a maximum of 3.0 mg/kg, during electrophysiologic testing. The results were compared to procainamide, which was also administered intravenously to 1000 and then to 1500 mg. Cibenzoline provided protection against ventricular tachycardia induction in 16 of 33 patients. The PR interval increased 13%, QRS duration widened 26%, and QTc interval was prolonged by 7%. There was a 9% fall in mean arterial blood pressure. Procainamide prevented ventricular tachycardia induction in 21 out of 31 patients tested. The PR interval increased 11%, QRS duration widened 27%, and QTc interval prolonged by 8%. Cibenzoline was given orally to 13 patients for chronic treatment. Chronic oral cibenzoline therapy after a mean follow-up of 8.8 months caused a reduction of ventricular ectopy from 666 to 190 beats/hr. Ventricular tachycardia events decreased per Holter monitor recording from 6 to 0.6. Cibenzoline therapy was discontinued in 5 of 13 patients due to break-through arrhythmias (nonsustained ventricular tachycardia on Holter monitor and recurrence of symptoms). Cibenzoline may be an effective antiarrhythmic agent in selected patients.