Intravenous quinidine in congestive cardiomyopathy

Single-dose pharmacokinetics of sotalol in a pediatric population with supraventricular and/or ventricular tachyarrhythmia

The pharmacokinetics (PK) of the antiarrhythmic sotalol, which elicits Class III and beta-blocking activity, has not been adequately defined in a pediatric population with tachyarrhythmias. The goal of this single-dose study with administration of sotalol HCl at a dose level of 30 mg/m2 body surface area (BSA) was to define the PK of the drug in the following four age groups: neonates (0-30 days), infants (1 month to 2 years), younger children (> 2 to < 7 years), and older children (7-12 years) with tachyarrhythmias of either supraventricular or ventricular origin. The drug was administered in an extemporaneously compounded syrup formulation prepared from the tablets containing sotalol HCl. For safety, vital signs and adverse events were recorded and the QTc interval and heart rate telemetrically monitored. Scheduled blood samples were taken over a 36-hour time interval following dose administration. The drug concentrations in plasma were measured by a sensitive and specific LC/MS/MS assay. Standard compartment model-independent methods were applied to compute the salient PK parameters of sotalol. Twenty-four clinical sites enrolled 34 patients. Thirty-three had analyzable data. Sotalol was rapidly absorbed, with mean peak concentrations occurring 2 to 3 hours after administration. The elimination of sotalol was characterized by an average half-life of between 7.4 and 9.2 hours in the four age groups. There existed statistically significant linear relationships between apparent total clearance (CL/f) or apparent volume of distribution (V lambda z/f) after oral administration and the covariates BSA, creatinine clearance (CLcr), body weight (BW), or age. The best predictors for CL/f were CLcr and BSA, whereas BW best predicted the V lambda z/f. The total area under the drug concentration-time curve in the smallest children with a BSA < 0.33 m2 was significantly greater than that in the larger children. This finding indicated that the BSA-based dose adjustment used in this study led to a larger exposure in the smallest children, whereas the exposure to the drug was similar in the larger children. The dose of 30 mg/m2 was tolerated well. No serious drug-related adverse events were reported. It can be concluded that the PK of sotalol in the pediatric patients depended only on body size, except for the neonates and smallest infants in whom the disposition of sotalol was determined by both body size and maturation of eliminatory processes.

Prospective comparison of intravenous quinidine and intravenous procainamide in patients undergoing electrophysiologic testing

BACKGROUND

Intravenous procainamide hydrochloride is frequently used in the acute care setting and during electrophysiologic testing, but intravenous quinidine gluconate is rarely used because of concerns about its safety. This study prospectively compares the hemodynamic and electrophysiologic effects of these agents in patients undergoing electrophysiologic testing.

METHODS AND RESULTS

Sixty-five consecutive patients with inducible ventricular tachyarrhythmias were prospectively treated with either intravenous quinidine gluconate or intravenous procainamide hydrochloride in an alternating unblinded fashion. The hemodynamic and electrophysiologic effects of these two drugs were compared. Seven (22%) patients assigned to intravenous quinidine gluconate and eight (24%) patients assigned to intravenous procainamide hydrochloride were rendered noninducible for ventricular tachyarrhythmias. Four (13%) patients assigned to intravenous quinidine gluconate were unable to complete the infusion compared with none (p = 0.05) assigned to intravenous procainamide hydrochloride. Otherwise, the overall hemodynamic and electrophysiologic effects of the two drugs were similar.

CONCLUSIONS

Intravenous quinidine gluconate is a reasonable alternative to intravenous procainamide hydrochloride in patients requiring a parenteral type IA antiarrhythmic agent.

Pharmacodynamic comparison of L-bunolol with propranolol, metoprolol, and placebo

Twelve healthy volunteers received single oral doses of propranolol (80 mg), metoprolol (100 mg), L-bunolol (2 mg), and placebo in a four-way crossover study. Blood pressure, ventricular rate, and echocardiographically determined ejection fraction, ejection time, and mean rate of circumferential fiber shortening (mVcf) were measured before dosing and at multiple time points during 10 hours after each dose, with subjects maintained in the supine position. Reductions in systolic and diastolic blood pressure following administration of each of the beta blockers were greater than those observed with placebo, but differences among the four treatments were not significant. Heart rate reductions with the beta blockers differed significantly from placebo (P less than .001), but differences among the three beta blockers were not significant. Differences among the four treatments in mVcf decrement did not attain significance at the 5% level (.05 less than P less than .1), and there were no significant differences in ejection-time prolongation or ejection-fraction reduction. Thus, reduced blood pressure, heart rate slowing, and reduced cardiac contractility may be associated with placebo treatment and may indicate the need for placebo controls in studies of the cardiovascular effects of beta blockers. Despite differing secondary pharmacologic properties, the three beta blockers reduced heart rate to a similar extent. Other effects of the beta blockers on blood pressure and cardiac contractility could not be consistently distinguished from those associated with placebo.

Pharmacokinetics and dynamics of penbutolol in humans: evidence for pathway-specific stereoselective clearance

The pharmacokinetics and dynamics of the D- and L-isomers of the beta-adrenergic blocking agent penbutolol were investigated in healthy human volunteers. In Study One, subjects received a single 40-mg oral dose of L-penbutolol (the pharmacologically active stereoisomer), and matching placebo on two occasions. A mean peak serum penbutolol concentration of 268 ng/ml was reached at 0.9 h after dosing. Elimination half-life averaged 1.6 h, and total clearance 16.6 ml/min per kg body weight. Changes in blood pressure, ventricular rate, and rate of circumferential fiber shortening (Vcf) did not differ between L-penbutolol and placebo. In Study Two, subjects received 40 mg D-penbutolol, L-penbutolol, and placebo on three occasions. Total clearance of D-penbutolol was higher than for the L-isomer (43.7 vs 15.9 ml/min/kg; P less than 0.01); this was reflected in correspondingly increased area under the serum concentration curve for conjugates of the oxidized metabolite 4-hydroxy penbutolol (2.25 vs 0.66 micrograms/ml X h; P less than 0.005). In contrast, direct conjugates of L-penbutolol achieved higher serum concentrations than conjugates of D-penbutolol. Alterations in blood pressure, ventricular rate, and Vcf for D-penbutolol, L-penbutolol, and placebo were quantitatively small. Thus the clearance of penbutolol after oral administration in humans is stereoselective, but the oxidative pathway is more stereosensitive than the parallel conjugative pathway. Penbutolol causes minimal alterations in parameters of cardiac function after single 40-mg doses in healthy humans.

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.

Safety and efficacy of intravenous quinidine

The safety and efficacy of intravenous quinidine were evaluated in a patient population with a high prevalence of left ventricular dysfunction and intraventricular conduction delays. Quinidine gluconate (mean dose 9.1 +/- 1.6 mg/kg) was administered during electrophysiologic study to 100 patients with ventricular or supraventricular tachyarrhythmias. Clinical heart failure was present in 68 percent of the patients. Left ventricular end-diastolic pressure, cardiac index, and left ventricular ejection fraction were abnormal in 62, 48, and 70 percent, respectively. Major intraventricular conduction delays (QRS of 120 msec or more) were present in 27 percent, and the H-V interval was prolonged (over 55 msec) in 28 percent. Despite the prevalence of these abnormalities, quinidine was discontinued because of hypotension in only 10 patients. Saline solution was infused to maintain preload in 37 percent, and hypotension responded promptly to saline solution infusion or discontinuation of quinidine infusion in all subjects. Hypotension was not more common in patients with more severe left ventricular dysfunction. QRS duration, H-V interval, QTc, and right ventricular effective refractory period increased significantly (p less than 0.001) after quinidine administration. Heart block or QRS widening of 50 percent or more did not occur. Quinidine prevented arrhythmia induction in 26 percent of patients who received full doses. Ventricular tachycardia cycle length increased in all 41 patients in whom identical forms were induced before and after quinidine (287 +/- 71 msec versus 361 +/- 93 msec, p less than 0.001). Intravenous quinidine may be administered safely to patients with intraventricular conduction delays and moderate heart failure. When antiarrhythmic efficacy is assessed by electrophysiologic study, quinidine compares favorably with other antiarrhythmic agents.