Pirmenol for control of ventricular arrhythmias: oral dose-ranging and short-term maintenance study

Profiles of aprindine, cibenzoline, pilsicainide and pirmenol in the framework of the Sicilian Gambit. The Guideline Committee for Clinical Use of Antiarrhythmic Drugs in Japan (Working Group of Arrhythmias of the Japanese Society of Electrocardiology)

The Vaughan Williams classification has been used widely by clinicians, cardiologists and researchers engaged in antiarrhythmic drug development and testing in many countries throughout the world since its initial proposal in the early 1970s. However, a major criticism of the Vaughan Williams system arose from the extent to which the categorization of drugs into classes I-IV led to oversimplified views of both shared and divergent actions. The Sicilian Gambit proposed a two-dimensional tabular framework for display of drug actions to solve these problems. From April to December 1996, members of the Guideline Committee met to discuss pharmacologic profiles of 4 antiarrhythmic drugs (aprindine, cibenzoline, pilsicainide, and pirmenol) that were not included in the original spreadsheet but are used widely in clinical practice in Japan. The discussion aimed to fit the drug profiles into the Gambit framework based on all the important literature published to date regarding the actions of the 4 drugs. This report is a summary of that deliberation.

Pharmacokinetics of pirmenol enantiomers and pharmacodynamics of pirmenol racemate in patients with premature ventricular contractions

The pharmacokinetics and pharmacodynamics of pirmenol were investigated in 12 patients with premature ventricular contractions (PVCs) after oral administration of racemic pirmenol, 100 mg and 200 mg every 12 hours. Holter monitoring was performed and serial blood samples were collected after the seventh doses. Plasma concentrations of pirmenol enantiomer were determined using a stereospecific liquid chromatographic assay. Clearance of total (-)-pirmenol was 20% higher than that of total (+)-pirmenol, and the difference in unbound clearance was 45% between enantiomers. Total pirmenol showed a smaller difference because of stereoselective protein binding, with 25% (100-mg dose) or 27% (200-mg dose) higher fraction unbound for (+)-pirmenol than for (-)-pirmenol. Distribution volume was similar for both enantiomers. Dose-dependent clearance was observed for unbound pirmenol enantiomers, as both enantiomers showed 20% lower unbound clearance at the higher dose. Antiarrhythmic effect (% reduction in PVCs from baseline) was correlated with plasma concentrations of pirmenol using a sigmoid maximum drug effect model, and patients showed a large variability in their antiarrhythmic response to plasma concentrations of pirmenol. The median value for minimum effective plasma concentration of racemic pirmenol was 1.5 micrograms/mL.

Clinical effects and pharmacokinetics of a single oral dose of pirmenol hydrochloride

To establish the clinical efficacy of a single oral dose of pirmenol, we evaluated electrophysiologic and hemodynamic effects simultaneously after drug administration, performing electrophysiologic testing in 20 patients with ECG-documented paroxysmal supraventricular tachycardia (PSVT) before and after a single oral 200-mg dose of pirmenol. Hemodynamic measurements were made with a Swan-Ganz catheter in the first 10 consecutive patients. In a different series of patients, we administered a single 200-mg oral dose of pirmenol to evaluate its acute termination effect in 7 patients with PSVT and 9 with paroxysmal atrial fibrillation. Pirmenol prolonged the refractory period of the retrograde conduction system in patients with or without an accessory pathway, and supraventricular tachycardia was no longer inducible at 60 min in 11 patients [8 of 11 with atrioventricular (AV) reentrant tachycardia and 3 of 5 with AV nodal reentrant tachycardia]. Pirmenol increased the heart rate (p < 0.01) and total systemic resistance (p < 0.05), and reduced the stroke volume index (p < 0.01), all significantly. The plasma concentration of pirmenol at 1 h after administration was 0.75 +/- 0.48 microgram/ml. A single oral dose of pirmenol during tachyarrhythmia successfully restored sinus rhythm in 4 of 7 (57%) patients with PSVT and 4 of 9 (44%) patients with paroxysmal atrial fibrillation. A single oral dose of pirmenol was well tolerated as episodic treatment in patients with supraventricular tachyarrhythmias.

Pirmenol: an antiarrhythmic drug with unique electrocardiographic features--a double-blind placebo-controlled comparison with quinidine

Previous reports have stated that pirmenol is a Class IA antiarrhythmic drug that prolongs the QT interval, but did not use computerized electrocardiography. We randomized 18 patients with frequent ventricular ectopic depolarizations to pirmenol (8 patients) or quinidine (10 patients). Pirmenol was effective and tolerated for suppression of arrhythmia in all 7 patients treated (1 patient withdrew for personal reasons) but quinidine was effective and tolerated for 4 weeks in only 5 of 10 patients (p less than 0.05). Using computerized 12-lead electrocardiography, the mean change in PR interval from placebo to treatment was 5 +/- 18 ms for quinidine and 5 +/- 11 ms for pirmenol (p = NS). The mean change in QRS interval was 5 +/- 14 ms for quinidine and 10 +/- 5 ms for pirmenol (p = NS). The mean change in QT interval was 46 +/- 30 ms for quinidine and 8 +/- 9 ms for pirmenol (p less than 0.01) and the mean change in JT interval was 41 +/- 36 ms for quinidine and -2 +/- 10 ms for pirmenol (p less than 0.01). After the double-blind phase, 4 quinidine patients had computerized electrocardiographic intervals measured on pirmenol; the above findings were confirmed. These electrocardiographic features of pirmenol clearly distinguish it from quinidine, the prototype Class IA drug. However, pirmenol has minimal effect on the PR and QRS intervals, and thus does not appear to be a Class IC drug either. Although its electrocardiographic features are closest to Class IB, its electrophysiology in isolated cells and its antiarrhythmic and side effect profile are atypical for a IB agent.(ABSTRACT TRUNCATED AT 250 WORDS)

Reassessment of benefit-risk ratio and treatment algorithms for antiarrhythmic drug therapy after the cardiac arrhythmia suppression trial

The Cardiac Arrhythmia Suppression Trial (CAST) has led to serious reconsideration of both the benefit-risk ratio of antiarrhythmic drug therapy and the appropriate therapeutic approach to various cardiac arrhythmias. Class IC drugs, such as encainide and flecainide, should not be used to treat asymptomatic postinfarction arrhythmias. Furthermore, because the CAST raises serious questions about the concept of treating asymptomatic but "potentially malignant" (prognostically important) arrhythmias guided by ambulatory monitoring, the prophylactic use of any of the antiarrhythmic agents (except beta blockers) must be considered inappropriate and potentially harmful until otherwise established by specific clinical trials. For prophylaxis of malignant ventricular arrhythmias (sustained ventricular tachycardia or ventricular fibrillation), treatment may still begin with standard agents in classes IA, IB, or both, preferably guided by electrophysiologic testing alone or in combination with noninvasive testing. Class IC therapy may be most useful in those patients in this group who do not have such high-risk characteristics for proarrhythmia as a history of multiple myocardial infarctions (MIs), congestive heart failure, or low ejection fraction. Amiodarone is moderately effective for treating these arrhythmias but is reserved as second- or third-line therapy because of its potential organ toxicity. Sotalol, a beta blocker with class III activity, is often effective and relatively well tolerated in these patients and may become a preferred drug when approved. For symptomatic but nonmalignant ventricular arrhythmias, a more conservative approach is more appropriate than in the past, with therapy reversed for those with debilitating symptoms. An initial trial of beta blockade is often appropriate before class I agents are considered.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical implications of new studies in the treatment of benign, potentially malignant and malignant ventricular arrhythmias

For purposes of clinical management, ventricular arrhythmias have been divided into risk categories of benign, prognostically important (potentially malignant) and malignant. Benign arrhythmias occur in the setting of structurally normal hearts and do not require therapy unless associated with debilitating symptoms. Malignant arrhythmias such as sustained ventricular tachycardia or fibrillation deserve aggressive therapy to prevent recurrence. Arrhythmias occurring in the presence of organic heart disease (often ischemic disease) are frequently asymptomatic but prognostically important as a risk factor for sudden death or cardiac arrest. The common empiric practice to treat such arrhythmias (by about 40 to 50% of cardiologists in the United States) needs to be reassessed in the face of the Cardiac Arrhythmia Suppression Trial. For malignant arrhythmias, class IA agents (procainamide and quinidine) continue to be the standard of treatment, and class IB agents (e.g., mexiletine) may be used as alternative or additive therapy. Class IC agents are used as second-line therapy, especially in the setting of ischemic heart disease. Class III therapy with amiodarone is reserved for refractory patients because of potential toxicity. Sotalol, a new class II-III agent, may become a first-line drug. For prognostically important arrhythmias, beta blockers remain the agents of choice, class IC agents are contraindicated, and class IA or IB drugs, or both, should be used conservatively (i.e., only for symptomatic arrhythmias). For symptomatic but benign arrhythmias requiring treatment, beta blockers are safe although not always effective. Class IA, IB and IC agents may then be considered. In these patients, the proarrhythmic potential of quinidine and class IC agents remains a concern.(ABSTRACT TRUNCATED AT 250 WORDS)

Recent antiarrhythmic drugs

Clinical failure of antiarrhythmic drugs often occurs in practice. Therefore, there is a need for new, effective and long-acting drugs with a wide therapeutic range and a low level of toxicity. Most new class I compounds block the fast sodium ion inward current of myocardial cells. According to their effects on the recovery kinetics of the sodium ion channel, these drugs are classified into 3 groups: IA (intermediate--cibenzoline, pirmenol, hydroxy-3-S-dihydroquinidine, quinacainol); IB (fast--tocainide, moricizine); IC (slow--flecainide, encainide, propafenone, lorcainide, indecainide, recainam and penticainide). Class IC drugs greatly depress intracardiac conduction and are the most potent antiarrhythmic compounds able to suppress ventricular premature beats. However, it is doubtful that long-term suppression of ventricular arrhythmias will improve survival of the patients. Some new drugs have been developed belonging to other classes: class II, esmolol, a new ultrashort-acting beta blocker; class III, N-acetyl-procainamide and sotalol, which prolong duration of the action potential and increase ventricular refractoriness; class IV, the mixed sodium ion-calcium ion-potassium ion antagonist, bepridil. The pharmacologic properties and the clinical effects of these new antiarrhythmic drugs are reviewed. However, future therapeutic trends will depend on the results of large multicenter clinical secondary prevention trials such as the Cardiac Arrhythmia Suppression Trial. New antiarrhythmic drugs with original electrophysiologic profiles and minimal adverse effects must prove their ability not only to suppress arrhythmias but also to reduce sudden cardiac death rate.

Effects of pirmenol hydrochloride on the spontaneous action potentials and membrane current systems of rabbit sinoatrial node cells

The electrophysiologic effects of pirmenol hydrochloride on rabbit sinoatrial node cells were examined and compared with those of several class I antiarrhythmic agents. At 1 microM, pirmenol decreased the heart rate and the rate of diastolic depolarization and increased the action potential duration at half-amplitude. Above 10 microM, the agent also decreased the maximum rate of rise (Vmax) and the action potential amplitude significantly. The order of the inhibitory potency on Vmax was apridine greater than 711389-S greater than pirmenol greater than mexiletine greater than tocainide. With respect to the current systems, pirmenol decreased the slow inward current (Isi) and the time-dependent potassium outward current (IK). The agent also prolonged the recovery time constant of Isi without any changes in the decay process of the tail current (IK). These findings suggest that pirmenol depresses the spontaneous discharge of the sinoatrial node through a decrease in Isi and Ik.

Efficacy and pharmacokinetics of oral pirmenol, a new antiarrhythmic drug

Pirmenol is a new orally effective antiarrhythmic agent. Reported are the results of oral administration of pirmenol to six patients (age 48.5 +/- 8.6 years, weight 83 +/- 15 kg) with stable ventricular extrasystoles (PVCs)--average ectopy rate 1040 +/- 630/hr (mean +/- SD). Patients received oral doses of placebo or 200 mg of pirmenol in a double-blind cross-over fashion followed by a single-blind rising-dose administration of 250 mg and 300 mg of pirmenol. The time period between doses was 48 hours. Pirmenol was rapidly absorbed (time to peak plasma levels 1 to 1.5 hours) and the mean maximum plasma concentrations were 1.8, 2.7 and 3.4 micrograms/mL with 200-mg, 250-mg and 300-mg doses, respectively. The elimination half-life was 9.3 +/- 3.0 hours and 31 +/- 14% of the dose was recovered in urine. The response criterion (80% suppression of PVCs of control for 8 hours) was met after the 300-mg dose in three patients. In three patients greater than 80% reduction occurred for up to 8 hours after the 200-mg dose. Pirmenol administration was not associated with any significant changes in blood pressure, heart rate, hepatic and renal function, PR interval or QRS duration. LV ejection fraction determined echocardiographically decreased from 63.0 +/- 6.9% predose to 59.7 +/- 5.0% about 2 hours after the 300-mg dose and QT interval increased by less than 10%. Two patients complained of transient bad taste sensation. Our results suggest that 250 mg to 300 mg of pirmenol, administered twice a day will suppress the PVCs effectively.

Long-term efficacy of oral pirmenol in suppressing ventricular premature depolarizations

Pirmenol is an investigational type 1A antiarrhythmic drug the long-term efficacy of which has not been fully determined. Therefore the long-term efficacy of oral pirmenol in suppressing ventricular premature depolarizations (VPDs) was assessed in an open-label, dose-titration study. Twelve patients (eight men and four women; mean age 57 +/- 12 years) were treated for 24 to 36 months (mean 33 +/- 4). Seven had structural heart disease (three valvular heart disease, two ischemic heart disease, and two hypertensive heart disease) and five did not. The mean left ventricular ejection fraction was 0.63 +/- 0.13. Exclusion criteria included less than 30 VPDs/hr, greater than 15 beats of ventricular tachycardia (VT), or prior failure of more than two antiarrhythmic drugs. Drug efficacy was assessed by 24-hour ambulatory ECG monitoring performed every 3 months during the first year, every 4 months during the second year, and at 6-month intervals during the third year. The mean hourly frequency of VPDs during the placebo phase was 732 +/- 608. Seven patients (58%) were treated successfully with effective (greater than 75%) long-term suppression of VPDs. Two patients (17%) had a partial response with effective suppression of VPDs for the first 16 months and 5 months of treatment, respectively. Three patients failed to show consistent suppression of VPDs while receiving pirmenol. The daily dose of pirmenol ranged from 200 to 500 mg (mean 317 +/- 94 mg at the beginning of the study and 375 +/- 97 mg at the end). No proarrhythmic effects were identified during long-term treatment, and none of the patients withdrew from the study prematurely.(ABSTRACT TRUNCATED AT 250 WORDS)

The relation of the kinetics of pirmenol to its antiarrhythmic efficacy

In a single-blind study the multiple oral dose kinetics of pirmenol were related to its efficacy in eight patients with frequent (mean, 631; range, 167-1374 beats/hour) premature ventricular contractions (PVC). Oral pirmenol was started at 100 mg bid for 48 hours and increased to 150 mg bid in six patients to obtain more than 70% suppression of PVC counts. Efficacy was achieved without side effects. Pirmenol decreased heart rate but not PR interval, QRS duration, or QTc interval. Peak plasma levels after the first 100-mg dose occurred at 1 to 3 hours and ranged from 0.6 to 1.9 micrograms/mL. Plasma elimination half-life ranged from 9.7 to 31 hours (mean, 18.3). From 67.4 to 171.3 mg pirmenol (mean, 102.3 mg) were recovered in the urine in 48 hours after the last dose. Cumulative excretion in divided urine collections was consistent with a mean elimination half-life of 15 to 20 hours. The pharmacokinetics of pirmenol support oral twice-daily administration. The minimum PVC suppressing plasma level is between 0.5 and 1.5 micrograms/mL.

Comparative efficacy of pirmenol and procainamide in a drug-resistant population with ventricular tachycardia

The acute antiarrhythmic properties of pirmenol were studied in 12 patients who failed clinical oral drug therapy with a history of a cardiac arrest or sustained ventricular tachycardia (VT). Programmed electrical stimulation studies were performed in ten men and two women with a mean age of 63 +/- 2 years. All patients had inducible ventricular tachycardia by programmed electrical stimulation when they were off all antiarrhythmic therapy. Patients were then tested on procainamide, 1000 mg, administered intravenously, and ventricular tachycardia could be provoked in nine of twelve patients. Pirmenol was given intravenously, 1.1 mg/kg bolus followed by 40 micrograms/kg/min over 40 minutes prior to drug testing. Pirmenol did not significantly change the baseline heart rate, blood pressure, or measured electrocardiographic values from control values. Ten of 12 patients were still inducible to ventricular tachycardia on pirmenol. Procainamide protected one of nine patients against VT induction. In patients still inducible on drug therapy, the VT rate was significantly slowed from 221 beats/min to 166 beats/min on pirmenol and to 200 beats/min on procainamide. The effects of this new antiarrhythmic agent were similar to procainamide in this drug-resistant study population.

Preclinical and clinical pharmacokinetics of pirmenol

Metabolic disposition and pharmacokinetics of pirmenol were studied in laboratory animals and in patients with premature ventricular beats. After intravenous administration, pirmenol pharmacokinetics were adequately characterized by a 2-compartment body model with elimination half-lives of 3 to 4 hours in animals and 6 to 9 hours in patients. Oral absorption of pirmenol was complete and devoid of significant first-pass metabolism. Systemic oral bioavailability averaged 87% in humans. Pirmenol was 83% to 90% bound to human plasma proteins. Animal studies showed that pirmenol was widely distributed in tissues resulting in higher drug concentrations in tissue than in plasma. Pirmenol was partly eliminated as unchanged drug and partly metabolized. Tracer studies in animals showed that approximately 40% to 50% of the administered radioactive dose was excreted in the urine and the remainder in the feces. The latter route was due to excretion of radioactivity in the bile. Evidence of enterohepatic recycling was established in bile duct-cannulated monkeys. Approximately 23% to 31% of the administered pirmenol dose was recovered unchanged in human urine.

A multicenter dose-response study of pirmenol hydrochloride in patients with ventricular premature contractions

The efficacy of pirmenol in suppressing ventricular premature complexes (VPCs) was assessed in 196 patients in a placebo-controlled, double-blind, multicenter study. At a daily dosage of 200 to 400 mg, pirmenol was effective in suppressing VPCs. In the double-blind phase of the trial, 60% of patients had at least a 70% reduction in VPC frequency and at least 70% of those patients who entered the open-label phase of the study continued to show at least a 70% reduction in VPC rate. Pirmenol was well tolerated by most patients; 66% of the patients treated with pirmenol in the double-blind phase had no adverse experiences. Of those who did have an adverse experience, the most common complaint was unusual taste. Serious adverse reactions were rare and only 2% of the patients had what may have been a proarrhythmic response. The same pattern of tolerance was seen in the open-label phase of the study when 151 patients were treated for an extended length of time with pirmenol. Pirmenol shows considerable promise for patients in whom the reduction of VPC frequency is desirable. Currently available antiarrhythmic drugs may have limited efficacy, cause serious or intolerable side effects or require frequent administration. Pirmenol has a convenient twice-daily dosing regimen, dependable antiarrhythmic action and a good safety record. This study demonstrated the effectiveness and safety of pirmenol in the control of VPCs.

Pirmenol in the termination of paroxysmal supraventricular tachycardia

The effects of pirmenol in terminating paroxysmal supraventricular tachycardia were studied in 25 patients. Pirmenol was administered as 1 or 2 injections of 50 mg to 17 patients during a spontaneous attack, or as a 50-mg bolus followed by steady infusion of 2.5 mg/min in 8 patients during a tachycardia that was induced electrophysiologically. Termination was successful in 11 of 17 patients who had a spontaneous attack and in 3 of 8 patients who had induced tachycardia. Pirmenol was effective in 3 of 5 patients with atrioventricular nodal reentrant mechanism, but in none of 3 patients with a reentrant tachycardia with a retrogradely conducting atrioventricular bypass tract. Conversion to sinus rhythm was achieved in 14 of 25 patients (56%). No hemodynamic adverse effects occurred. Pirmenol increased the atrial effective refractory period, but had little effect on conduction in the atrioventricular node and His-Purkinje system. Reentry was abolished through a block in the retrograde part of the dual atrioventricular nodal pathway, which is typical of class I antiarrhythmic agents.

Electrophysiology and antiarrhythmic efficacy of intravenous pirmenol in patients with sustained ventricular tachyarrhythmias

We assessed the electrophysiologic effects and antiarrhythmic efficacy of intravenous pirmenol in 15 patients who had spontaneous and induced sustained ventricular tachyarrhythmias. At a plasma concentration of 2.29 +/- 0.75 micrograms/ml, pirmenol decreased sinus cycle length by 11 +/- 13%, increased QRS, QTc, and HV intervals by 14 +/- 12%, 13 +/- 12%, and 22 +/- 28%, respectively, and increased atrial and ventricular effective refractory periods (ERP) by 20 +/- 14% and 7 +/- 8%, respectively. There was a greater increase in QRS duration during ventricular tachycardia and ventricular pacing than during sinus rhythm (p less than 0.005). By electropharmacologic testing, pirmenol was judged effective in six patients (40%) and was proarrhythmic in one (6%). In the nine patients in whom pirmenol was judged ineffective, the cycle length of induced VT increased by 36 +/- 15% and the associated mean arterial pressure increased by 21 +/- 14 mm Hg. The only side effects were mild hypotension and mild nausea in one patient each. Intravenous pirmenol has type IA electrophysiologic effects. It can be administered safely to patients with sustained ventricular tachyarrhythmias and is as effective as approved antiarrhythmic drugs when assessed by electropharmacologic testing.

Electrophysiologic actions of pirmenol in dogs with recent myocardial infarction

The electrophysiologic actions of pirmenol, an investigational class I antiarrhythmic agent, were evaluated in eight anesthetized dogs, 5 to 10 days after anterior myocardial infarction. Before administration of the drug, programmed ventricular stimulation failed to initiate nonsustained or sustained ventricular tachyarrhythmias (VT) in any of the postinfarction dogs. After the cumulative administration of 2.5, 5.0, and 10.0 mg/kg pirmenol, programmed stimulation initiated sustained VT in six of the eight postinfarction dogs tested, with one additional dog responding with reproducible nonsustained VT (15 to 20 monomorphic complexes) after pirmenol administration. Only one of eight postinfarction dogs tested remained noninducible throughout the pirmenol dosing schedule. Administration of pirmenol tended to increase ventricular excitation thresholds, relative (p less than 0.05 after 10 mg/kg) and effective refractory periods in ischemically injured ventricular myocardium, and increased the difference or disparity in relative (p less than 0.05 after 5.0 and 10.0 mg/kg) and effective (p less than 0.01 after 2.5, 5, and 10, mg/kg) refractory periods between ischemically injured and normal noninjured ventricular myocardium. These findings suggest a potential for the provocation or aggravation of ventricular arrhythmias by pirmenol in the setting of recent myocardial infarction.

Pirmenol in termination of paroxysmal supraventricular tachycardia

An assessment was made of the effect of pirmenol in the termination of paroxysmal supraventricular tachycardia (SVT). Sinus rhythm was restored by intravenous administration in 11 of 17 patients during a spontaneous attack. Another 8 patients were studied electrophysiologically. Pirmenol terminated an induced SVT in 3 of 5 patients having an atrioventricular (AV) intranodal re-entry mechanism but in none of 3 patients having an atrioventricular bypass tract as one re-entrant limb. The overall success in restoring sinus rhythm was 14 of 25 patients (56%). The drug was hemodynamically well tolerated even in cases of continued SVT. Pirmenol increased the atrial effective refractory period and had no obvious effect on AH and HV intervals. The functional refractory period of the AV node was decreased, probably by an anticholinergic effect. The effective and functional refractory periods of retrograde atrioventricular conduction via the AV node and bypass tract were increased in some patients. The mechanism terminating the AV intranodal SVT was a block in the retrograde part of the dual AV nodal pathway, a typical antiarrhythmic Class I effect.

Acute electrophysiologic effects of pirmenol in normal subjects and in patients with Wolff-Parkinson-White syndrome

The acute electrophysiologic effects of pirmenol are reported in 8 normal subjects and in 8 patients with Wolff-Parkinson-White (WPW) syndrome. Standard electrophysiologic testing was performed before and after a 50-mg intravenous bolus and a 60-minute infusion of 150 mg of pirmenol. After pirmenol administration, AH interval, atrial refractory period, atrioventricular (AV) nodal functional refractory period and Wenckebach cycle length did not change; however, sinus cycle length decreased from 743 +/- 169 to 650 +/- 133 ms (p less than 0.001), sinoatrial conduction time from 103 +/- 35 to 78 +/- 37 ms (p less than 0.05) and AV nodal effective refractory period from 308 +/- 51 to 272 +/- 23 ms (p less than 0.01). Pirmenol increased the HV interval from 43 +/- 5 to 48 +/- 6 ms (p less than 0.05) and ventricular functional refractory period from 247 +/- 21 to 260 +/- 21 ms (p less than 0.005). Anterograde effective refractory period of the accessory AV pathway increased in 4 of 6 patients with ventricular preexcitation and retrograde effective refractory period increased in all patients. Pirmenol treatment prolonged the shortest preexcited RR interval from 253 +/- 38 to 459 +/- 19 ms (p less than 0.05) and the average RR interval from 354 +/- 26 to 421 +/- 60 ms (p less than 0.01) during atrial fibrillation in all 6 patients with preexcitation. Pirmenol did not influence the inducibility or cycle length of AV reciprocating tachycardia in the patients with WPW syndrome. The pirmenol infusions were well tolerated.(ABSTRACT TRUNCATED AT 250 WORDS)

Conversion of paroxysmal atrial fibrillation to sinus rhythm by intravenous pirmenol. A placebo controlled study

The efficacy of pirmenol (a class I antiarrhythmic agent) as a converter of paroxysmal atrial fibrillation was investigated. Forty patients without congestive heart failure or a history of sinus node disorder were randomly allocated to receive either intravenous pirmenol (50-100 mg) or placebo in a double blind trial. In 12 of 20 patients sinus rhythm was restored 2-16 minutes after pirmenol, and in 3 of 20 patients in the control group it returned within one hour. A nodal escape rhythm was seen during sinus slowing in one patient, but in other patients there was no sinus arrest, atrioventricular conduction disturbance, or hypotension. The ventricular rate was slightly increased in patients in whom sinus rhythm was not restored by pirmenol. The results indicate that pirmenol has an antifibrillatory effect on the atria. Sinus rhythm was restored rapidly after intravenous administration. It was well tolerated in patients with atrial fibrillation of recent onset.

Initial and long-term outpatient experience with pirmenol for control of ventricular arrhythmias

Pirmenol, a new class IA antiarrhythmic agent, has shown promise in short-term trials, but long-term efficacy has not been documented. We thus evaluated 11 patients with frequent (greater than or equal to 60/h) premature ventricular complexes (PVC) given oral pirmenol for 25-727 days. Ten of 11 patients entering the long-term open trial had shown greater than or equal to 70% (mean 83%) PVC suppression during in-hospital pirmenol dose ranging. Long-term pirmenol was given in divided doses of 100-600 mg/day. Mean PVC frequency during baseline was 13,078/24 h (range, 3,218-32,718); couplets averaged 481/24 h (1-2,829) and runs 45/24 h (0-334). Ambulatory monitoring was performed at 1, 3, 6, and 12 months, then semiannually. Mean absolute PVC suppression at 1 month averaged 75% (p less than or equal to 0.02). Median individual percentage PVC suppression was 94%. During the first 3 months, 8 patients (73%) continued to show a favorable response (greater than or equal to 70% suppression), and 3 had arrhythmia recurrence and were dropped. One responder was withdrawn after the onset of paroxysmal atrial fibrillation, and another early responder was withdrawn after 3 months because of arrhythmia relapse. Six patients have been treated for over 1 year, with 99% mean PVC suppression. Mean couplet and run frequencies at 1 month decreased by means of 76% (p less than or equal to 0.05) and 92% (p = 0.001) respectively. At 1 year, couplets were suppressed 99.8% and runs by 99.7% in the 6 patients remaining on pirmenol.(ABSTRACT TRUNCATED AT 250 WORDS)