Propafenone: a new agent for ventricular arrhythmia

Propafenone, a new antiarrhythmic agent, was utilized in 30 patients with diverse heart disease who presented with sustained hemodynamically unstable ventricular arrhythmia. Drug efficacy was judged by means of ambulatory electrocardiographic monitoring and exercise testing. Nine patients additionally had invasive electrophysiologic studies. Seventeen patients (57%) responded to therapy as judged by monitoring and 21 patients (70%) responded to therapy as judged by exercise testing. When both methods were considered, 16 patients (53%) responded. The acute drug test predicted the result of maintenance therapy in 91% of patients. Seven of nine patients who had electrophysiologic testing responded based on this technique, and in all cases the results were concordant with the noninvasive evaluation. Serum blood levels did not correlate with antiarrhythmic effect. In patients with myocardial impairment, echocardiographic assessment of left ventricular function indicated a decrease in ejection fraction during propafenone therapy (32 versus 24%, p less than 0.05), while no change was observed in patients with normal left ventricular function. Side effects occurred in nine patients and included exacerbation of congestive heart failure, development of conduction abnormalities and aggravation of arrhythmia, each occurring in two patients. Ten patients who continued on long-term propafenone therapy for an average of 10 months (range 3 to 13) have remained free of arrhythmia and side effects. Propafenone needs to be employed with caution in patients with congestive heart failure or evidence of conduction system disease.

Effects of propafenone on induction and maintenance of atrioventricular nodal reentrant tachycardia

Electrophysiologic studies were performed in 10 patients with atrioventricular (A-V) nodal reentrant paroxysmal supraventricular tachycardias (PSVT), before and after intravenous administration of propafenone (1.5 mg/kg). All patients utilized an A-V nodal slow pathway for anterograde conduction and an A-V nodal fast pathway for retrograde conduction of the reentrant impulse. Propafenone depressed retrograde fast pathway conduction which was manifested by: 1) complete V-A block at all ventricular paced cycle lengths after propafenone in 3 cases; 2) increase in mean +/- SD of ventricular paced cycle length producing V-A block from less than 308 +/- 37 ms to 432 +/- 63 ms in the remaining 7 patients. Nine of the 10 patients had induction of sustained PSVT before propafenone. In 7 of the 9, PSVT could not be induced or sustained after propafenone, reflecting depression of the retrograde fast pathway conduction with either absence of atrial echoes (5 patients) or induction of nonsustained PSVT, with termination occurring after the QRS (2 patients). In 1 patient, single atrial echoes were induced before propafenone but none were noted after the drug. In only 2 patients was a sustained PSVT inducible after propafenone. In conclusion, propafenone inhibited induction of sustained A-V nodal reentrant PSVT in most patients, reflecting depression of retrograde A-V nodal fast pathway conduction.

[Combinations of some anti-arrhythmia drugs]

The need to treat severe and repetitive arrhythmias which are often resistant to treatment with single different drugs has led to an increasing interest towards associations of antiarrhythmic drugs. The advantages of this associations could be: enhancing effect of different pharmacological properties, synergism, reduction of doses and side-effects. The risks are: induction or aggravation of excitability and conduction disturbances, impairment of contractility, hypotension, interaction with digoxin. This study describes our experience in using associations of antiarrhythmic drugs of different classes (IA + II, IA + III, IB + III) or of the same class (IA). We also report our preliminary results with the use of Propafenon-Amiodarone association in the acute treatment of electrophysiologically induced ventricular tachycardias and in the chronic treatment of repetitive and symptomatic ventricular tachycardias. Our experience demonstrates that the association of antiarrhythmic drugs is effective in the treatment of severe and repetitive arrhythmias only if the patients are carefully selected and the risks of unwelcome electrophysiological actions and side-effects are taken into account.

[Propafenone in refractory supraventricular arrhythmias]

Twelve patients with ventricular arrhythmias were given 300-900 mg oral of propafenon daily. We have obtained VT's suppression in 6 of 8 cases (75%) and "complex" VEB's suppression or significant reduction in 6 of 10 cases (60%). Total VEB have been strongly reduced (-91,2%) in 7 of 12 patients (58,3%). The effects of Propafenon on electrocardiographic intervals have not been significant at lower doses and only with 900 mg we have noted a significant (p less than 0,05) lengthening of the P-R (+27,1%) and QTc (+10,2%) intervals. Propafenon has never caused important negative inotropic effects. These results have been confirmed during a follow-up period of 5-19 months. In conclusion we believe that Propafenon must be considered a highly efficient drug for the treatment and prevention of refractory ventricular arrhythmias.

Electrophysiologic and hemodynamic effects of intravenous propafenone in patients with recurrent ventricular tachycardia

Electrophysiologic and hemodynamic studies were performed before and after intravenous infusion of a new antiarrhythmic agent, propafenone, in 28 patients with recurrent ventricular tachycardia. Propafenone was given at a loading dose of 2 mg/kg in all patients. Subsequently, group A, the first 14 patients, received 1 mg/min and group B, the second 14 patients, received 2 mg/min continuous infusion. Propafenone exerted no effect on sinus nodal recovery time and sinoatrial conduction time, but significantly prolonged atrioventricular (AV) nodal and His-Purkinje conduction time and the QRS duration (respectively, 95 +/- 19, 48 +/- 10 and 120 +/- 23 ms before, and 110 +/- 28, 53 +/- 10 and 135 +/- 27 ms after; p less than 0.001). Propafenone did not change the mean arterial blood pressure but slightly increased right atrial, pulmonary artery and capillary wedge pressures resulting in mild depression of the cardiac index (2.6 +/- 0.8 liters/min per m2 before and 2.3 +/- 0.7 liters/min per m2 after; p less than 0.001). None of the patients were symptomatic from these changes. In group A, propafenone did not affect the inducibility of ventricular tachycardia except for one patient whose arrhythmia was sustained before and become nonsustained after propafenone. In group B, sustained ventricular tachycardia became noninducible in three patients and nonsustained in two patients, and nonsustained ventricular tachycardia became noninducible in one patient after propafenone. Therefore, an appropriate loading dose of intravenous propafenone such as 2 mg/kg followed by 2 mg/min infusion may be given safely and may suppress ventricular tachycardia. Propafenone may be a useful addition to currently available antiarrhythmic agents.

[Electrophysiologic effects of propafenone in subjects with pre-existing excito-conduction disorders]

Few data are currently available regarding the electrophysiological effects of Propafenon administration in patients with pre-existing excito-conduction system disturbances. We have performed electrophysiological evaluation in 18 patients (15 males and 3 females, mean age 61 +/- 9 years - 4 patients with sinus bradycardia, 5 pts with AVN block, 4 patients with bundle branch block and normal HV and 5 patients with bundle branch block and prolonged HV) before and after intravenous administration of Propafenon (1 mg/Kg B.W. in 5 minutes). Propafenone administration decreased the heart rate, significantly lengthened AH and HV intervals, lengthened atrial, ventricular and, above all, AVN refractory periods. In no cases sinus pauses, marked bradycardia, spontaneous A-V block or additional intraventricular conduction disturbances were observed. We conclude that: due to its marked electrophysiological effects on AVN and His-Purkinje system, Propafenon is electively indicated for the treatment of ventricular arrhythmias and paroxysmal supraventricular tachycardia with AVN reentry; Propafenon intravenous administration appears to be safe also in pts with preexisting excitation and conduction disturbances.

[Hemodynamic effects of propafenone in acute myocardial infarct]

The hemodynamic effects of Propafenon were evaluated in 11 patients with acute myocardial infarction complicated by atrial and/or ventricular arrhythmias (atrial fibrillation in 4 cases, atrial premature beats in 3 cases, ventricular premature beats Class II-IVa in 4 and rapid sustained ventricular tachycardia in one case). Drug was administered as a bolus of 1-2 mg/kg in 5 min, followed by a 10-15 gamma/kg/min infusion for 24 hours in 7 patients. Serial measurements were taken of heart rate, systemic blood pressure, right atrial, pulmonary and capillary wedge pressure, cardiac output, cardiac index, total systemic resistances, left ventricular stroke work index, left ventricular ejection time and left ventricular mean ejection rate (LVMER) (8 cases) and PEP/LVET ratio (5 cases). After the intravenous bolus, a significant reduction of cardiac index (p less than 0.01) and LVMER (p less than 0.05) parallel to an increase of total systemic resistances and PEP/LVET ratio (p less than 0.01 and p less than 0.05 respectively); was observed no other parameter varied significantly. The peak hemodynamic effect was observed after 10 minutes and return to normal required from 30 minutes to 3-6 hours in the more severely affected patients. No late negative inotropic action was evident in 6 out of 7 patients who received long term infusion. Suppression or greater than 80% reduction of premature beats was evident in 9/12 cases. Sinus node function, atrioventricular and intraventricular conduction, and the QTc interval did not vary significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

[Comparative evaluation of mexiletine and propafenone by dynamic electrocardiography]

We have compared the efficacy of Propafenon and Mexiletine in 12 subjects (7 males and 5 females, age range of 22-61 year) affected by chronic ventricular extrasystolic beats. Propafenon and Mexiletine were orally administered in doses of 900 mg/day and 600 mg/day respectively in a single blind, cross-over fashion. Our results show that: Propafenon is better tolerated; Propafenon has caused a statistically significant reduction of the total number of ventricular ectopic beats/24 hours; the efficacy of Propafenon has been greater than that of Mexiletine (66% and 25% respectively); with both drugs, in 2 cases, there was an increase of the total number of ventricular ectopic beats/24 hours; Propafenon has induced clear-cut electrocardiogram changes (statistically significant lengthening of P-Q and Q-T intervals).

[Comparative study on the efficacy of disopyramide and propafenone in the prevention of the recurrence of ventricular tachycardia]

The purpose of our study was to assess the efficacy of Propafenon in comparison with Disopyramide in the long-term treatment of repetitive ventricular tachycardia. We studied 34 patients suffering from episodes of repetitive ventricular tachycardia of different etiology. Propafenon and Disopyramide was administered in doses of 300 mg and 200 mg three times a day respectively. The number of ventricular tachycardias has been evaluated during a period of 4 months of basal observation and during two periods of 4 months each of treatment respectively with Disopyramide and Propafenon. Moreover a dynamic electrocardiogram was recorded to assess the efficacy of Propafenon in suppressing ventricular ectopic beats in 17 patients. We conclude that Propafenon shows greater efficacy than Disopyramide in the treatment of repetitive ventricular tachycardias and a comparable efficacy in the control of ventricular ectopic beats. Moreover Propafenon shows also a minor incidence of side effects.

[Clinical experience with propafenone in paroxysmal supraventricular reciprocating tachycardias]

We studied the long term antiarrhythmic efficacy of Propafenon, (300-900 mg/day) in 25 patients (18 females, 7 males; mean age 37,6; follow-up 10 +/- 9,3 months) affected by episodes of disabling paroxysmal supraventricular reciprocating tachycardia. We performed an electrophysiologic study using cardiac catheterization in all 25 patients. Fifteen patients had a Wolff-Parkinson-White syndrome; in 8/25 pts the reentrant circuit was in the atrio-ventricular node and in 2/25 pts it was into the atrium. Ten of fifteen patients with Wolff-Parkinson-White syndrome and 5/8 patients with the reentrant circuit in the atrio-ventricular node have been treated with Propafenon according to the results of the acute test performed during electrophysiologic study. Good results (no recurrences of paroxysmal supraventricular reciprocating tachycardia or less frequent recurrences at a much slower heart rate) have been obtained in 13/15 patients with Wolff-Parkinson-White syndrome and in 5/8 patients with the reentrant circuit in the atrio-ventricular node. The acute drug test with Propafenon during electrophysiologic study was predictive of the clinical response in 100% of patients with Wolff-Parkinson-White syndrome and in 60% of patients with the reentrant circuit in the atrio-ventricular node. We conclude that: 1) Propafenon may be good alternative to Amiodarone in the chronic treatment of pts affected by paroxysmal supraventricular reciprocating tachycardia, especially in patients with Wolff-Parkinson-White syndrome; 2) electrophysiologic study to evaluate Propafenon efficacy is most valuable in patients with Wolff-Parkinson-White syndrome.

[Experimental characterization of propafenone. Hemodynamic effects]

We studied the haemodynamic effects of Propafenon in a group of 20 subjects who had a coronary arteriography and a left ventriculography. The drug was been administered in doses of 1 mg/kg b.w. i.v. in 5 minutes. The haemodynamic parameters were measured in basal conditions and after 10 and 20 minutes. The basal data and those obtained after 20 minutes were analyzed and compared statistically. Our results show that Propafenon administered acutely i.v. in therapeutic doses causes a very small depression of cardiac inotropism. The same results were obtained in subjects whose basal haemodynamic parameters were abnormal. Our data show that the drug can be used safely also in subjects with mild heart failure.

[Comparison of the efficacy of propafenone and hydroquinidine in stabilized extrasystolic ventricular arrhythmia by means of dynamic electrocardiographic Holter monitoring]

The aim of our study has been to evaluate the efficacy of Propafenon by a reliable experimental method. We have compared the efficacy of Propafenon (300 mg three times daily) with that of Dihydroquinidine Chloride at an elevated dose (300 mg six times daily). Twelve patients, with chronic arrhythmia (at least 1500 premature ventricular beats - PVBs - during a preliminary 24-hour dynamic electrocardiographic Holter monitoring), have been studied. The study has been performed in a double-blind cross-over fashion, and the drugs were administered according to a randomized sequence by the double dummy technique for 4 days. Placebo administration periods of similar duration were established before, after and between the two periods of drug administration. At the end of each Propafenon Dihydroquinidine Chloride and Placebo administration period a 48-hour Holter monitoring was performed. The number of PVBs/hour measured during the 3 periods of Placebo administration (714 +/- 418, 804 +/- 422, 779 +/- 433 respectively) confirmed the chronic nature of the ventricular arrhythmia and the absence of spontaneous variations during the study. Treatment with Propafenon and Dihydroquinidine Chloride significantly reduced the number of PVBs/hour to 87 +/- 130 and to 216 +/- 453 respectively. The reduction observed during Propafenon administration was more than observed during Dihydroquinidine Chloride administration, but it was not statistically significant because of the different behaviour of the individual patients. All patients but one had an over 65% reduction of PVBs/h; only 8/12 patients showed a reduction greater than 65% during Dihydroquinidine Chloride administration.(ABSTRACT TRUNCATED AT 250 WORDS)

[Electrophysiologic characterization of propafenone in man]

We performed an electrophysiologic study in 10 subjects before and after administration of Propafenon in doses of 1,5 mg/Kg b.w. i.v. in 2-3 minutes. No symptoms and no significant reductions of arterial blood pressure were observed. The analysis of our data shows that Propafenon does not significantly influence the sinus node function and the sinoatrial conduction. As far the atrioventricular conduction, the drug caused a significant increase of the Wenckebach point, of St-Q interval duration and of the A-V node absolute refractory period. The H-V interval and the His-Purkinje refractory period were also increased. We conclude that P exerts a negative dromotropic effect by direct pharmacological action on the A-V node and on the intraventricular specific conduction pathways.

[Electrophysiologic effects of propafenone in patients with sinus node dysfunction]

The electrophysiologic effects of intravenously administered Propafenon (1,5 mg/kg) were evaluated in 16 patients (mean age: 62,1 +/- 11 years) with sinus node dysfunction, shown by sinus bradycardia or intermittent sino-atrial block. The variations of sinus cycle length were not statistically significant (NS), (1137,1 +/- 244,9 msec versus 1191,9 +/- 321,1 msec). In one patient sinus rate markedly decreased from 36 to 28 beats/min. In 2 patients the cycle length of a junctional rhythm was comparable before and after drug administration; in both patients the rate of the junctional rhythm decreased and in one markedly (from 39 to 32 beats/min). Sinoatrial conduction time increased in 4 patients and decreased in 6. The variations were not statistically significant (223,8 +/- 76 msec versus 230,6 +/- 75,9 msec). In one patient the sinoatrial conduction time which was normal during the control study, could not be evaluated after Propafenon due to the appearance of a retrograde block between the atrium and the sinus node. Maximum corrected sinus node recovery time was prolonged by the drug in 9 patients and shortened in 5. In 2 patients the sinus node recovery time was prolonged to about 10 sec. The mean value of corrected sinus node recovery time increased from 883,6 +/- 995,8 msec to 1820,5 +/- 2894 msec (NS). Propafenon significantly prolonged the effective refractory period and the functional refractory period of the atrium, as well as the A-H, H-V and QRS intervals, the A-V node functional refractory period, the relative refractory period of His-Purkinje system and the ventricular effective refractory period.(ABSTRACT TRUNCATED AT 250 WORDS)

[Electrophysiologic and anti-arrhythmia properties of propafenone deducible from experimental studies in vitro]

The aim of our study was to analyze which of the basic "in vitro" properties of Propafenon could be relevant to the antiarrhythmic action, as well as to contribute to its classification among the antiarrhythmic drugs. Propafenon belongs to class 1 of Singh and Hauswirth's classification and its characteristics are similar to those of lidocaine; Propafenon may act mainly on ventricular arrhythmias caused by a reentry circuit or by increased automaticity including those which occur in the post-ischemic state and those due to digitalis toxicity. A peculiar aspect of Propafenon seems, however, to be the beta-receptor blocking activity (especially beta-2) shown at therapeutical doses. Such property can induce a depression of heart rate and contractility mainly in patients with a compensatory increase of the sympathetic tone. On the contrary, the calcium-antagonist action of Propafenon is very weak, as it is detected only at doses 80-100 times higher than those that exert an electrophysiologic action. It is also possible that the pharmacological activity of the drug "in vivo" can assume aspects different from those expected from "in vitro" experiments, because of the various metabolites of Propafenon demonstrated in human beings.

[Clinical pharmacology of propafenone]

Aim of our study is to examine some aspects of the relationship between pharmacokinetics and pharmacodynamics of Propafenon that are important as far as its current use is concerned. Orally administered Propafenon is largely absorbed and easily metabolized by the liver. Bioavailability is on the average 50%. Ninety per cent of the administered dose is eliminated in the feces and in the urine in about 60 hours. Because of the lack of a good correlation between chronically administered doses and plasmatic concentration, we tried to see whether the peak concentration after administration of a single dose could predict in some way the response of the patients arrhythmia. So far we do not have a clear cut answer to this question, which probably requires a different, more complex approach to the relations between pharmacokinetics, plasmatic levels and therapeutic range of an antiarrhythmic drug.

[How and why treat supraventricular tachycardias]

The present study deals with pathophysiological and clinical aspects of two major supraventricular tachyarrhythmias: atrial fibrillation and reciprocating tachycardia. The main hemodynamic effects and the most frequent complications are examined, and therapeutic indications are given concerning pharmacologic, surgical or electrical treatment. Twelve patients with supraventricular tachycardia (5 with intranodal reentry and 7 with A-V by-pass tract) were treated with Propafenone and evaluated by repeated electrophysiological testing. Acute infusion of Propafenone (2 mg/kg over 10 minutes) interrupted the induced tachycardia in 9 of 11 patients (81%); Propafenone prevented the induction of the arrhythmia in 60% of patients with nodal reentry and in none with A-V by-pass. Electrophysiological evaluation repeated after one week of oral treatment (300 mg three times daily) in 5 patients indicated complete protection in two patients; in three the arrhythmia was still inducible but had a significantly lower rate. Finally, with regard to electrical treatment, data are presented concerning 10 patients with supraventricular reentrant tachycardia (4 intranodal, 6 with A-V by-pass tract) in whom an antiarrhythmic pacemaker was implanted (5 type Pasar Telectronics, 5 type Medtronic SP 500). The results were highly favourable in 9 patients with complete control of the arrhythmia.

Effect of propafenone on the membrane currents of rabbit sino-atrial node cells

The effects of propafenone (1-50 micrograms/ml) on the membrane potential and currents of the rabbit sino-atrial node were studied using the voltage clamp technique. Propafenone decreased the heart rate, amplitude of the action potential and maximum rate of depolarization. It also depolarized the maximum diastolic potential and the resting potential and prolonged the action potential duration dose dependently. On the current systems of the sino-atrial node, propafenone reduced the outward current (ik), the inward current activated by hyperpolarization (ih) and the slow inward current (is) dose dependently. The decrease in is and ik by propafenone was due to the reductions in their conductance, not to the changes in the voltage dependence of the inactivation of is or activation of ik. The decrease in ik might be the ionic mechanism of the negative chronotropic effect of propafenone.

Electrophysiologic and hemodynamic effects of propafenone, a new antiarrhythmic agent, on the anesthetized, closed-chest dog: comparative study with lidocaine

The relative hemodynamic and electrophysiologic effects of a new antiarrhythmic drug, propafenone, and lidocaine were evaluated in eight closed-chest, anesthetized dogs. Propafenone (4 mg/kg intravenously) significantly (p less than 0.05) lowered aortic and pulmonary systolic pressures and caused a rise in heart rate (p less than 0.05). Cardiac output decreased from 4.5 +/- 1 to 3.8 +/- 0.7 L/min (p less than 0.05) during atrial pacing at 400 msec cycle length. Propafenone had no effect on pulmonary and aortic diastolic pressures. Lidocaine (5 mg/kg intravenously) caused a significant (p less than 0.05) decrease in aortic systolic pressure and a rise in heart rate. Lidocaine had no significant effect on the other measured hemodynamic parameters. Propafenone, unlike lidocaine, significantly (p less than 0.05) increased atrioventricular nodal functional refractory period and right ventricular endocardial (apex) cathodal (0.5 +/- 0.1 mA to 1.9 +/- 0.3 mA) and bipolar (1.4 +/- 0.3 to 2.2 +/- 0.4 mA) diastolic excitability threshold. Propafenone, unlike lidocaine, also caused a significant (p = 0.05) intraatrial conduction delay; however, neither drug caused conduction slowing in the His-Purkinje system. Both drugs had no effect on sinus nodal recovery time and on the effective refractory period of the right ventricular endocardium (apex). Mean plasma propafenone levels during hemodynamic and electrophysiologic measurement ranged between 3.2 +/- 1.8 micrograms/ml and 1.7 +/- 1.1 micrograms/ml. All of the propafenone-induced effects were reversible within 90 minutes. We conclude that propafenone differs from lidocaine in its atrial, AV nodal, and ventricular electrophysiologic properties, and thus these may explain propafenone's greater efficacy over lidocaine against both certain atrial and ventricular arrhythmias.(ABSTRACT TRUNCATED AT 250 WORDS)

Fatal ventricular tachycardia in association with propafenone, a new class IC antiarrhythmic agent

A man with a past history of malignant ventricular arrhythmias occurring late after myocardial infarction was admitted for assessment. Monitoring revealed frequent ventricular premature beats and occasional non-sustained runs of ventricular tachycardia. Other drugs having failed, he was started on oral propafenone which is a new Vaughan Williams class IC antiarrhythmic agent. Several hours after starting this drug he had incessant ventricular tachycardia and subsequently died. Other class IC agents have been shown to have a high incidence of proarrhythmic effects, and particular care should be taken with these potent new drugs.

Demonstration of beta adrenoceptor blockade by propafenone hydrochloride: clinical pharmacologic, radioligand binding and adenylate cyclase activation studies

The postulated beta adrenoceptor blocking properties of the new antiarrhythmic drug propafenone were studied by in vivo comparison against placebo and propranolol in the antagonism of both exercise- and isoproterenol-induced tachycardia and by in vitro radioligand binding studies of animal and human left ventricular muscle membrane preparations. Interaction with frog erythrocyte membrane adenylate cyclase was also investigated. In the clinical studies, a double blind crossover comparison of oral propafenone (300 mg), propranolol (40 mg) and placebo indicated significant antagonism of chronotropic response to isoproterenol 2 hr postdose with dose ratios of 4.1 +/- 1.3 (mean +/- S.E.M.) for propafenone and 16.8 +/- 5.1 for propranolol. Chronotropic response to exercise was modestly reduced by propafenone. Analysis of the binding of [125I]iodocyanopindolol to human left ventricular membranes revealed specific beta adrenoceptor competition by propafenone with an EC50 of 111 +/- 13 nM. Propranolol EC50 was 2.4 +/- 0.2 nM in this system. Competitive inhibition of isoproterenol-stimulated frog erythrocyte membrane adenylate cyclase activity was also obtained with propafenone. The ratio of affinities (calculated from the apparent dissociation constant; KD) for propranolol-propafenone was 1:40 for the in vivo study and 1:50 for the in vitro system. Propafenone is a specific antagonist of the human beta adrenoceptor and this action can be demonstrated during in vivo study in human subjects. At clinical dosages it appears likely that it will achieve a modest degree of beta blockade which may contribute to its antiarrhythmic effect.

The multiple modes of action of propafenone

Previous studies of widely different concentrations of propafenone in various species have reported that in addition to having class 1 antiarrhythmic action, the drug was a beta adrenoceptor blocker and a calcium antagonist. High concentration shortened action potential duration in animal experiments, but Q-T interval was reported as being lengthened in man. It was thought desirable to study the effects of propafenone over a range of concentrations equivalent to those used clinically in various cardiac tissues of a single species, the rabbit. It was concluded that although the primary action of propafenone was on fast inward current, the drug being categorised as of group 1c, its potency as a beta blocker was sufficient for the effect to be of clinical significance. Its potency as a calcium antagonist was relatively weak. Action potential duration and effective refractory period were lengthened in both atrium and ventricle, the effects being long-lasting and persisting on wash-out of the drug when other measurements had returned to control values.

Studies on the metabolism of propafenone. 1st Comm.: synthesis and chromatographic/mass spectrometric properties of the labelled compound and of the reference substances

The synthesis of 14C-propafenone and 2H-propafenone (propafenone: 2-(2'-hydroxy-3'-propylamino-propoxy)-omega-phenyl-propiophenone hydrochloride) and some reference compounds is described. The thin-layer chromatographic, high-performance liquid and gas chromatographic properties of the substances are described. Propafenone and the reference substances were studied by mass spectrometry and compared with each other, with respect to structural elucidation of the metabolites. The chromatographic and mass spectrometric data (key ions) enables the metabolites of propafenone to be identified in biological material.

The metabolic fate of 2H-labelled propafenone in man

The metabolism of propafenone was studied in three humans by using 300 mg of the deuterated compound given orally. The excretion of propafenone and its metabolites was assessed by measuring the deuterium content in the excretion products by means of a microwave plasma detector. At selected times the metabolic pattern in plasma, urine, bile and feces was determined. The metabolites were isolated and the structure of the main compounds was characterized. Propafenone is absorbed completely and quantitatively metabolized. Unchanged propafenone is excreted neither in the urine nor in the feces in amounts of more than 1% the dose. The percentage of free unconjugated propafenone of the total deuterium content in the plasma was about 10% 3 and 6 hours after application. Conjugates of hydroxylated derivatives of propafenone are present predominantly in the plasma. The excretion of the metabolites takes place mainly by way of the feces, 53% of the dose is excreted by this route within 48 hours. Urinary elimination accounted for 18.5 and 38% of the dose within 48 hours in two humans. It was possible to elucidate the structure of 11 metabolites, accounting for more than 90% of the dose administered. The major metabolites are conjugates of 5-hydroxypropafenone and hydroxy-methoxy-propafenone with glucuronic and sulphuric acid and propafenone glucuronide. Furthermore, metabolic products of oxydative deamination pathway were identified, i.e. a glycol and a lactic acid derivative. C-C splitting yields a relatively large amount of 3-phenyl-propionic acid, while cleavage of the ether group leads to a phenolic product and is only of minor importance.

A controlled trial of propafenone for treatment of frequent and repetitive ventricular premature complexes

The effectiveness of oral propafenone was evaluated for the treatment of ventricular premature complexes (VPCs) in 12 patients, using a single-blind, dose-ranging trial followed by a double-blind comparison with placebo, and then an open-label, long-term protocol. During dose ranging, 8 of 12 patients achieved greater than or equal to 80% suppression of total VPCs (mean 83%) (p less than 0.01 vs single-blind placebo). Paired VPCs were suppressed greater than or equal to 90% and ventricular tachycardia was eliminated in 11 of the 12 patients (p less than 0.01). The effectiveness of propafenone for treatment of VPCs was confirmed during the double-blind trial (p less than 0.05 vs double-blind placebo) and during treatment for 6 months (p less than 0.05 vs initial single-blind placebo). Propafenone prolonged the PR interval by 16% (p less than 0.01 vs single-blind placebo) and the QRS interval by 18% (p less than 0.001). Left ventricular systolic performance decreased as assessed by 2-dimensional echocardiography (p less than 0.01 vs single-blind placebo). Propafenone increased serum digoxin levels in 5 of 5 patients (mean increase of 83%). Side effects included exacerbation of congestive heart failure (1 patient) and conduction abnormalities (2 patients). Thus, propafenone is effective for treatment of total and repetitive VPCs. Although generally well tolerated, the drug reduces left ventricular systolic function and atrioventricular conduction and increases serum digoxin levels.

Pharmacological studies on propafenone and its main metabolite 5-hydroxypropafenone

The new antiarrhythmic drug propafenone and its main human metabolite 5-hydroxypropafenone were investigated for antiarrhythmic, local anaesthetic, Ca++-antagonistic and beta-adrenoceptor blocking effects as well as for their activity on the central nervous system. In isolated organs (guinea-pig atria, rat aortic strips) 5-hydroxypropafenone had a smaller effect on the maximum following frequency, a greater negative inotropic effect, a greater Ca++-antagonistic effect and a very distinctly weaker beta-adrenoceptor blocking effect than propafenone. Consistent with its antiarrhythmic potency in vitro, intra-cutaneous 5-hydroxypropafenone had a smaller local anaesthetic effect in the guinea pig wheal. In contrast to these findings 5-hydroxypropafenone showed a stronger antiarrhythmic potency in vivo (rat and dog), as demonstrated on the aconitine- and infarction arrhythmias. In addition, in His bundle studies 5-hydroxypropafenone caused a more marked prolongation of the conduction time in atria, AV-node and His-Purkinje system. In vivo the beta-adrenoceptor blocking effect of 5-hydroxypropafenone (isoprenaline tachycardia, rat) was smaller than that of propafenone. The difference between the in vitro and in vivo potency of 5-hydroxypropafenone may be explained by differences in pharmacokinetics, e.g. by a smaller distribution volume compared to propafenone. CNS effects were investigated due to local anaesthetic properties of the substances tested. As indicator of CNS activity anticonvulsant effects, detectably beneath convulsion-inducing doses, were determined in rats (max. electroshock seizures). The results show low CNS activity of propafenone which is even lower for the metabolite but which is distinctly higher for lidocaine and - related to the antiarrhythmic potency - for flecainide, too.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical efficacy and electrophysiology of oral propafenone for ventricular tachycardia

Sixteen patients with ventricular tachycardia (VT) or nonfatal cardiac arrest were treated with propafenone (P), 900 mg/day. Electrophysiologic studies were performed before and during therapy with P. All patients had inducible sustained VT at the baseline study. During P therapy, VT was not inducible in 1 patient, was unsustained in 1 and was harder to induce in 2 patients. P increased the cycle length of VT from 307 +/- 67 to 382 +/- 107 ms. Five patients began outpatient therapy with P, including 2 in whom VT was slowed to less than 125 beats/min. Two are arrhythmia-free during follow-up of 2 and 8 months. P significantly increased intraatrial conduction time (from 44 +/- 12 to 72 +/- 22 ms), AH interval (from 115 +/- 36 to 152 +/- 45 ms), HV interval (from 55 +/- 18 to 92 +/- 42 ms), QRS duration (from 140 +/- 36 to 180 +/- 48 ms) and QT interval (from 402 +/- 30 to 459 +/- 60 ms). P increased atrial (from 247 +/- 36 to 288 +/- 38 ms) and ventricular (from 249 +/- 20 to 277 +/- 32 ms) effective refractory periods, Sinus cycle length did not change, but the corrected sinus node recovery time increased (from 162 +/- 85 to 821 +/- 1,607 ms). P aggravated arrhythmias in 4 patients. The plasma P concentration, measured either at the time of electrophysiologic studies of when therapy was discontinued, was 753 +/- 428 ng/ml. P suppressed ventricular ectopic beats in 33% and increased them in 1 patient. P has antiarrhythmic activity against VT similar to that of other antiarrhythmic drugs and has potential for serious adverse effects in some patients.

[Emergency treatment of arrhythmias in neonates and infants]

Emergency treatment of cardiac arrhythmias was required in 41 newborn and infants aged two days to 9 months (mean 77 days) from July 1977 until September 1981. Heart defects were present in 27 (65.8%). Invasive electrophysiological studies were performed in all patients. The different types of arrhythmias were: bradyarrhythmias in 9 (21.9%): bradycardia to cardiac arrest (5), congenital complete AV-block (3), postoperative complete AV-block (1). Tachyarrhythmias in 32 patients (78.1%): reentry through accessory connections (21), congenital atrial flutter (6), ventricular flutter/fibrillation (3), and AV-nodal tachycardia (2). Overdrive atrial or ventricular stimulation with a consecutive series of 15-20 impulses of 5-10 Volts abolished arrhythmic attacks in 22 patients including 4 in whom prior digitalization had no effect. In two other patients overdrive pacing achieved sinus rhythm only after i.v. Propafenon. In 4 further patients 36.2 to 63.8 mg/m2 i.v. Propafenon and in 4 other patients DC synchronized cardioversion with 1 to 3 Wsec/kg restored a normal heart rate. The 3 patients with congenital complete heart block died, one despite permanent pacing. Oral Propafenon therapy with 300 mg/m2 die in three divided doses following emergency therapy of tachyarrhythmias was discontinued in patients without arrhythmias after 1 year on drug therapy. There was no relapse after a mean follow-up period of 1.9 years. Only patients with congestive heart failure due to cardiac defects needed additional digitalisation. Thus, in our experience antiarrhythmic drug therapy with Propafenon was more effective in this age group than digitalization.

[Comparative studies on the cardiodepressant effect of disopyramide, mexiletine and propafenon]

The effect of clinical antiarrhythmic doses of disopyramide (Di), mexiletine (Me), and propafenon (Pr) on cardiac function was studied in 7 normal volunteers by M-mode echocardiography and the extent of functional changes caused by the three drugs was compared. For each of the substances echocardiographic parameters of left ventricular function were determined before injection, 5-25 min. after an intravenous administration (Di 2.0 mg/kg, Me 3.0 mg/kg, Pr 1.5 mg/kg) at intervals of 5 min., and after 3 days of oral therapy (Di 4 X 200 mg/day, Me 4 X 200 mg/day, Pr 3 X 300 mg/day). Di, Me, and Pr each showed significant negative inotropic activity, though of varying degree. For each drug the effect was more pronounced after intravenous administration than under oral therapy. Maximum decreases in myocardial contraction occurred 5-15 min. after termination of injection, with an increase in endsystolic diameter (Di 30.3%, Me 13.6%, Pr 9.7%), no change in preejection diameter, and a reduction in the percentage and velocity of mean circumferential fiber shortening and systolic ventricular wall thickness (Di 18.1%-45.1%, Me 9.6%-23.7%, Pr 11.8%-16.7%). While the cardiodepressant activity of orally administered Di, Me and Pr did not statistically differ, for the first 20 min. after intravenous administration Di exhibited a marked negative inotropic effect that was significantly greater than those of Me and Pr. In view of the considerable hemodynamic side effects of Di, Me, and Pr observed in this study, the benefit to risk ratio must be evaluated carefully and individually before commencement of antiarrhythmic therapy. Because of its acute and pronounced cardiodepressant activity, intravenous Di should be used with particular caution; a dose reduction and slow injection are recommended in patients with left ventricular dysfunction.

Clinical pharmacology of propafenone

We determined the efficacy, pharmacokinetics, and plasma concentration-response relationships of propafenone, a promising new antiarrhythmic drug. Thirteen patients with frequent and complex ventricular premature beats were studied after receiving four increasing doses, during drug washout and during a randomized double-blind placebo-controlled trial, to evaluate the optimal dose in each patient. A nonlinear relationship was found between propafenone dose and steady-state mean concentration with a 10-fold increase in drug concentration as dose increased threefold from 300 to 900 mg/day. There was great intersubject variability in elimination half-life (mean 6 hr, range 2.4 to 11.8), steady-state mean concentration on 900 mg/day of propafenone (mean 1008 ng/ml, range 482 to 1812), and "therapeutic" plasma concentration (mean 588 ng/ml, range 64 to 1044). The interaction of these three parameters in individual patients determined the duration of the antiarrhythmic action of propafenone during washout (mean 11.5 hr, range 4 to 22). There was a greater than 90% reduction of ventricular premature beats in 10 subjects during dose ranging and in seven during double-blind crossover. Side effects requiring discontinuation of the drug occurred in three patients and included apparent worsening of arrhythmias in two. We conclude that propafenone effectively suppresses ventricular arrhythmias and that nonlinear drug accumulation and intersubject variability in elimination of half-life, steady-state mean plasma concentration, and therapeutic concentration indicate a need for individual therapy.

[Esophageal ulcer caused by mexiletine]

The anti-arrhythmic drug mexiletine caused an oesophageal ulcer, confirmed by endoscopy and biopsy, in a 72-year-old woman. This side-effect has not previously been published. The clinical course was similar to that observed after oesophageal ulceration caused by other drugs. An ulcer in the piriform recess also developed in a 63-year-old man who was taking both acetylsalicylic acid and mexiletine: it cleared up after mexiletine had been discontinued.

Drug therapy of cardiac arrhythmias

The authors provide an overview of the general features of pharmacokinetics and report the pharmacodynamic and pharmacokinetic interactions of selected antiarrhythmic drugs. Their clinical experience in the use of investigational antiarrhythmic drugs is also presented.

New and old concepts in sarcoidosis

These discussions are selected from the weekly staff conferences in the Department of Medicine, University of California, San Francisco. Taken from transcriptions, they are prepared by Drs Homer A. Boushey, Associate Professor of Medicine, and David G. Warnock, Associate Professor of Medicine, under the direction of Dr Lloyd H. Smith, Jr, Professor of Medicine and Chairman of the Department of Medicine. Requests for reprints should be sent to the Department of Medicine, University of California, San Francisco, School of Medicine, San Francisco, CA 94143.

Beta-blocking and electrophysiological effects of propafenone in volunteers

The chemical structure of propafenone (P) and certain experimental findings suggest that this antiarrhythmic compound could possess beta-blocking properties. To evaluate the clinical relevance of the latter cardiovascular effects of P during exercise were studied. After oral administration of P 150 and 300 mg in solution, six healthy volunteers were subjected to graded exercise. These doses of P, which are usually effective against arrhythmias, decreased exercise-induced tachycardia, whereas the systolic blood pressure was lowered but only at rest, and the diastolic pressure was slightly raised. However, taking into account dose ratio, and the intensity and duration of the reduction in exercise tachycardia, this effect of P was only about 5% at its maximum compared to propranolol and similar active beta-blocking compounds. The reduction in heart rate produced by P was not correlated with the plasma level nor did it show dose dependency, in contrast to beta-blocking agents, and also in contrast to its electrophysiological effects on the PQ interval.

[The effect of disopyramide, mexiletine and propafenon after intravenous and oral administration on left ventricular function in the M-mode echocardiogram]

The effects of the antiarrhythmic drugs disopyramide (D), mexiletine (M), and propafenone (P) on left ventricular function after intravenous injection and after oral therapy of at least 48 hours, and of the combined oral application of D and M, were studied by M-mode echocardiography in patients with ventricular arrhythmias in whom antiarrhythmic therapy was indicated. The drugs were given in doses comparable in terms of clinical efficacy. The results showed that the three drugs had varying negative inotropic power. The intravenous injection resulted in a more pronounced cardiac depression than the oral therapy. The most significant decrease in left ventricular wall motion after intravenous and oral application was seen after D, the smallest negative inotropic effect after M. P caused a cardiac depression between these extremes. After the combined oral application of D and M the impairment of left ventricular function was more pronounced than after therapy with the single drugs.