Safety and efficacy of intravenous quinidine

Continuous intravenous quinidine infusion for the treatment of atrial fibrillation or flutter: a case series

BACKGROUND

The purpose of the study was to evaluate a continuous intravenous quinidine infusion (CIQI) for the treatment of cardiac arrhythmias in critically ill patients.

METHODS AND RESULTS

A 2-year retrospective review was conducted in adult patients receiving a CIQI for cardiac arrhythmias. Patient demographics, baseline laboratory values, indication for quinidine, dose, duration of therapy, efficacy, adverse events, and serum concentration were among the collected data. All patients were critically ill and receiving quinidine for the treatment of atrial arrhythmias. Quinidine was effective in 14 (61%) of the 23 enrolled patients. Ninety-one percent of the patients received the CIQI after surgery. A total of 8 (35%) patients died. Four (17%) patients had hypotension possibly attributed to the quinidine.

CONCLUSIONS

A continuous intravenous infusion of quinidine gluconate may be effective in patients in whom other agents are contraindicated or have failed. However, as with all antiarrhythmic agents, risks of therapy must be carefully considered.

Combination of sotalol and quinidine in a canine model of torsades de pointes: no increase in the QT-related proarrhythmic action of sotalol

INTRODUCTION

Clinical treatment with a combination of Class IA and III antiarrhythmic drugs is not recommended, as they both favor bradycardia-dependent proarrhythmic events such as torsades de pointes (TdP). However, this theoretical additive effect on ventricular repolarization has never been demonstrated and could be questioned as other Class I drugs, such as mexiletine, a Class IB drug, limit the number of sotalol-induced TdP in dogs with AV block, suggesting the possibility of an antagonistic action of Class I properties against Class III effects.

METHODS AND RESULTS

We compared the electrophysiologic and proarrhythmic effects of sotalol (Class III) alone and combined with quinidine (Class IA) in a canine model of acquired long QT syndrome. Seven hypokalemic (K+: 3 +/- 0.1 mEq/L) dogs with chronic AV block had a demand pacemaker implanted and set at a rate of 25 beats/min. They were submitted to two (sotalol-alone and sotalol-plus-quinidine) experiments 48 hours apart using a randomized cross-over protocol. They were pretreated with quinidine (10 mg/kg + 1.8 mg/kg per hour) or saline infused throughout the experiment, and given sotalol (4.5 mg/kg + 1.5 mg/kg per hour) for 2 hours, 30 minutes after the beginning of the pretreatment infusion during both experiments. Ventricular and atrial cycle lengths were similarly increased by sotalol after quinidine or saline. The sotalol-induced prolongation of the QT interval was significantly shorter in quinidine-pretreated dogs (24 +/- 7 msec after quinidine vs 40 +/- 8 msec after saline). Fewer dogs developed TdP: significantly during the first hour of infusion (1/7 sotalol-plus-quinidine vs 6/7 sotalol-alone dogs, P < 0.05) but nonsignificantly during the second hour (3/7 vs 6/7).

CONCLUSION

In this model, the sotalol-plus-quinidine combination is at least no more arrhythmogenic than either of the drugs given alone.

Parenteral antiarrhythmics for life-threatening ventricular arrhythmias

The acute management of life-threatening ventricular tachyarrhythmias often includes the use of parenteral antiarrhythmics. There are a number of agents currently available for this purpose. They are used to suppress inducible monomorphic ventricular tachycardia during programmed electrical stimulation, they terminate spontaneous sustained ventricular tachycardia, and prevent ventricular fibrillation in the setting of an acute myocardial infarction. Serious adverse reactions include proarrhythmia, hypotension, severe bradyarrhythmias, and precipitation of congestive heart failure. A comparative evaluation of intravenous antiarrhythmics is difficult due to inherent differences in the choice of agents for study, protocol design, patient population, defined endpoint, and serum drug levels. Likewise, the reported adverse reaction rates vary from 0.4% to 75%. To understand the difficulties in clinical decision-making in this problem area, particularly drug selection, we present here a review of pertinent clinical trials evaluating parenteral drug efficacy and adverse effects.

Quinidine: is it a good drug or a bad drug?

Although quinidine, the oldest class I antiarrhythmic drug, has been available for several decades, recent reports have emphasized the possibility of dangerous side effects. Quinidine often successfully maintains sinus rhythm in patients with intermittent atrial fibrillation, suppresses sustained ventricular tachycardia in some patients, and minimally depresses left ventricular function. However, it can cause nonfatal and, occasionally, even fatal proarrhythmic complications. Therefore, it must be administered with caution in appropriately selected patients.

Treatment of severe malaria in the United States with a continuous infusion of quinidine gluconate and exchange transfusion

During the past decade the incidence of Plasmodium falciparum malaria in the United States has increased 10-fold. Treatment may be delayed because the therapy recommended for severe or complicated disease, intravenous quinine dihydrochloride, is available only from the Centers for Disease Control. We studied 17 patients who were treated for severe or complicated P. falciparum malaria in the United States between 1985 and 1987. Five patients were treated with a continuous infusion of quinidine gluconate, 10 with an exchange transfusion in addition to the continuous infusion of quinidine gluconate, and 2 with intermittently administered intravenous quinine dihydrochloride and an exchange transfusion. All 16 patients with P. falciparum malaria (1 patient had P. vivax malaria) had hyperparasitemia at the time of diagnosis (6 to 54 percent of the erythrocytes infected; median, 13 percent). Three patients with marked hyperparasitemia (54, 38, and 30 percent) and multiple other indicators of a poor prognosis, including advanced age, died. The 13 patients who completed their courses of quinidine with or without exchange transfusion had a parasitemia level of 1.1 percent or less 28 to 72 hours (mean, 44.4 hours) after the start of therapy. Side effects of quinidine treatment were observed in only two patients, one of whom had a serum quinidine concentration above the toxic level. We conclude that the continuous infusion of quinidine gluconate is well tolerated alone and with exchange transfusion and is effective in the treatment of severe and complicated malaria.

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.

Hypoglycaemia and antimalarial drugs: quinidine and release of insulin

Life threatening hypoglycaemia has been closely associated with the use of quinine, but the effect of quinidine and the synthetic antimalarials on the homoeostasis of glucose has not been investigated. In volunteers given a fixed dose of 500 mg base and patients with malaria given a quinidine loading dose (15 mg base/kg) mean (SEM) plasma insulin concentrations rose from 6.1 (1.5) mU/l to 10.9 (4.4) mU/l (p less than 0.02) and 10.4 (2.0) mU/l to 18.5 (5.3) mU/l (p less than 0.04), respectively. Plasma glucose concentrations fell from 4.5 (1.1) mmol/l (81 (20) mg/100 ml) to 4.0 (0.3) mmol/l (72 (5) mg/100 ml) in volunteers (p less than 0.04) and from 5.7 (1.3) mmol/l (102 (23) mg/100 ml) to 4.8 (1.6) mmol/l (86 (29) mg/100 ml) in patients (p less than 0.05). One of two patients with cerebral malaria and acute renal failure became profoundly hypoglycaemic (plasma glucose concentration 1.4 mmol/l (25 mg/100 ml), plasma insulin concentration 3.1 mU/l). Hypoglycaemia may occur in any severely ill fasting patient given parenteral quinidine. The other antimalarials tested, chloroquine, amodiaquine, mefloquine, and halofantrine, did not stimulate the release of insulin, an important advantage that should be taken into account when treatment is chosen for Plasmodium falciparum malaria.

Intravenous quinidine: relations among concentration, tachyarrhythmia suppression and electrophysiologic actions with inducible sustained ventricular tachycardia

A computer simulation was used to devise quinidine sulfate infusions to produce pseudo-steady-state concentrations in the low (8 microM/liter) and high (14 microM/liter) therapeutic ranges, avoiding high peak concentrations. Using this infusion, efficacy and electrophysiologic actions of quinidine sulfate were assessed in 21 patients with sustained inducible ventricular tachycardia (VT) when concentrations were 12.6 +/- 11 microM/liter (mean +/- standard deviation) and 18 +/- 9 microM/liter. Although mean concentrations approximated target levels, there was substantial individual variation. A reciprocal linear relation (r = 0.8, p less than 0.01) was noted between resultant serum concentrations and drug-free ejection fraction (EF). Transient hypotension occurred early in 3 patients, 2 of whom had a normal left ventricular (LV) EF. No hemodynamic compromise was seen in patients with LVEFs of less than 30%. Induced VT was suppressed in 5 patients at low concentrations and in an additional 4 at high concentrations (total 9 of 21, 42%). Concentration-dependent changes in the ventricular effective refractory period of the beat induced by S3 paralleled antiarrhythmic efficacy. Independent of response or lack of response to intravenous quinidine, 17 patients received gradually increasing oral quinidine dosages adjusted to reproduce plasma levels that had been effective during intravenous administration, or to maximal well-tolerated dosage (if side effects occurred). VT was still inducible during oral treatment in 4 of 5 patients in whom VT had been suppressed during the intravenous infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Intravenous quinidine by intermittent bolus for electrophysiologic studies in patients with ventricular tachycardia

The safety and efficacy of intravenous quinidine gluconate, using intermittent boluses of 80 mg/cc every 5 minutes to a total dose of 800 mg, was evaluated in 61 patients referred for electrophysiologic studies (EPS). Patients were referred because of out-of-hospital cardiac arrest (12), symptomatic ventricular tachycardia (VT) (24), asymptomatic VT (18), syncope of unknown origin (6), and supraventricular arrhythmias (1). Clinical heart failure was present in 74% of patients, with a mean ejection fraction of 45 +/- 3 for all patients. Quinidine prevented VT induction in 78% of patients at a mean dose of 9.6 mg/kg and facilitated VT induction in 7% of patients. Quinidine failed to decrease mean arterial pressure in 14 patients, and in the remaining 47 patients arterial pressure decreased by 16%. Six patients had hemodynamically significant hypotension. Two patients had hypotension severe enough to require saline administration, while four had hypotension not needing fluid replacement. Sixteen percent of patients experienced other side effects. Quinidine can be administered safely by intermittent infusion and is effective in preventing programmed stimulation induction of VT. Carefully monitored, intravenous intermittent bolus administration of quinidine should be utilized more frequently in EPS, since significant adverse side effects are infrequent.