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Biomedical subjects

C Lebsack

Publications and source records attributed to C Lebsack.

7 recordsLinked to original sources
PubMed1991

Disposition kinetics of orally administered enoximone in patients with moderate to severe heart failure.

Enoximone is a phosphodiesterase inhibitor, which has been studied extensively for use in the management of patients with moderate-to-severe heart failure. The authors have studied the absorption and disposition kinetics of enoximone and its primary metabolite, enoximone sulfoxide, after both single oral doses of enoximone and at steady-state after short-term chronic oral therapy. A total of ten patients (two female, eight male) with moderate-to-severe heart failure (NYHA class II-IV) were enrolled into the study after giving written informed consent. The plasma levels of enoximone sulfoxide were greater than those of enoximone at all sampling times. The peak enoximone sulfoxide plasma concentrations ranged from 3.5 to 17.3 times the peak enoximone plasma levels for individual patients. The average steady-state plasma concentrations for enoximone were 115 +/- 40 ng/mL and 190 +/- 78 ng/mL for 50 mg every 8 hours and 100 mg every 8 hours dosage regimens, respectively. The absorption and disposition kinetics of enoximone were found to be significantly variable between patients. The authors also evaluated the relationship between dose administered and steady-state plasma levels as well as the relationship between the observed and predicted steady-state plasma levels. The authors found a linear relationship between the dose that was administered and the accrued plasma levels, as well as a good correlation between the predicted and observed steady-state levels. Although these data confirm previous reports that the sulfide metabolite of enoximone accumulates extensively in the plasma during oral therapy, reaching levels much higher than those of enoximone, these data do not support previous suggestions that the disposition of enoximone is nonlinear.

Administration, Oral↗
PubMed1991

Clinical pharmacology of intravenous enoximone: pharmacodynamics and pharmacokinetics in patients with heart failure.

Twenty-one patients with heart failure (New York Heart Association [NYHA] class II to IV) received a 24-hour infusion of enoximone followed by a 12-hour washout period. Patients were randomly assigned to one of four treatment groups. Groups I to III received an 0.5 mg/kg bolus, followed by a maintenance infusion of 2.5, 5.0, or 10.0 micrograms/kg/min. Group IV patients received a maintenance infusion of 5.0 micrograms/kg/min without a loading dose. Serial assessment of hemodynamics, plasma levels of enoximone and enoximone sulfoxide, and ventricular ectopy were performed. Enoximone produced a clinically significant increase in cardiac index, and a decrease in mean pulmonary artery wedge pressure and systemic vascular resistance in all groups. Enoximone mildly increased heart rate, and had a minimal effect on mean arterial pressure. There was no statistically significant change in ventricular ectopy during the infusion. Significant hemodynamic improvement was noted at even the lowest infusion rate, and did not increase in linear fashion at higher infusion rates. In patients who did not receive an initial loading bolus of 0.5 mg/kg, the increase in cardiac index was delayed by approximately 1 hour. Plasma concentrations of both enoximone and its major metabolite continued to rise throughout the 24-hour infusion in group III (10.0 micrograms/kg/min), rather than reaching steady state as predicted by the terminal exponential half-lives of these compounds. This is suggestive of nonlinear pharmacokinetics and indicates a potential for excessive accumulation of enoximone and its metabolite during prolonged infusion. These findings may have important implications in guiding the intravenous administration of enoximone.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

Pharmacodynamics of enoximone during intravenous infusion.

Twenty-one patients with heart failure (NYHA class II-IV) received a 24-hour infusion of enoximone, followed by a 12-hour washout period. Patients were randomly assigned to one of four treatment groups. Groups I-III received a 0.5 mg/kg bolus, followed by a maintenance infusion of 2.5, 5.0 or 10.0 micrograms/kg/minute. Group IV patients received a maintenance infusion of 5.0 micrograms/kg/minute without the bolus. Serial assessments of haemodynamics, plasma levels of enoximone and enoximone sulphoxide, and ventricular ectopy were performed. Enoximone produced a significant increase in cardiac index (28.1-46.7%) and a decrease in mean pulmonary artery wedge pressure (6.4-35.7%) and systemic vascular resistance (34.7-78.9%). Enoximone had minimal effect on heart rate and blood pressure. In patients who did not receive an initial bolus of 0.5 mg/kg, haemodynamic changes were delayed by approximately 1 hour. Significant haemodynamic improvement was noted at even the lowest infusion rate and did not increase in linear fashion at higher infusion rates. During infusion of enoximone at 10.0 micrograms/kg/minute, both enoximone and its sulphoxide accumulated non-linearly and did not achieve a steady state. No significant adverse effects were noted in these patients. Enoximone infusion at rates greater than 5.0 micrograms/kg/minute may confer minimal additional haemodynamic benefit, while resulting in significant accumulation of enoximone and enoximone sulphoxide. Ventricular ectopy did not increase significantly in most patients.

Cardiotonic Agents↗
PubMed1989

Clinical experience with sotalol in patients with drug-refractory ventricular arrhythmias.

Sixty-five patients with symptomatic, drug-refractory, sustained ventricular tachycardia or fibrillation were treated with oral sotalol (80 to 480 mg twice daily). Sotalol was withdrawn in 11 patients because of continued inducibility of ventricular tachycardia at the time of follow-up electrophysiologic study. Therefore, the clinical effectiveness of sotalol could be evaluated in 54 patients followed up for 11.5 +/- 6 months (range 0.2 to 25). The actuarial incidence of successful sotalol therapy was 54 +/- 13% at 6 months and 47 +/- 13% at 12 months. In 39 patients who underwent electrophysiologic testing while receiving oral sotalol, the drug prevented the reinduction of ventricular tachycardia/fibrillation in 8 (20%). During follow-up study, arrhythmia recurred in 1 (17%) of 6 patients whose ventricular tachycardia was noninducible with oral sotalol and in 8 (44%) of 18 with inducible tachycardia but who were continued on oral sotalol therapy. Adverse effects were noted in 28 patients (42%), requiring drug withdrawal in 13 (22%) and dose reduction after hospital discharge in 10 (15%). Exacerbation of ventricular arrhythmia occurred in six patients (9%), one of whom had associated hypokalemia. Sotalol is frequently useful in the control of intractable, life-threatening ventricular arrhythmias, and its efficacy appears to be predicted by programmed stimulation. However, there is a high rate of limiting side effects, which precludes its use in a large number of patients, and a substantial risk of arrhythmia exacerbation.

Administration, Oral↗
PubMed1988

Propafenone: a new antiarrhythmic agent.

The chemical and pharmacologic properties, pharmacokinetics, drug interactions, clinical efficacy, adverse effects, and dosage of propafenone are reviewed. Propafenone is a class IC antiarrhythmic agent that is structurally similar to the beta blockers but that has only weak beta-blocking and calcium-channel-blocking activity. It is well absorbed after oral administration, but systemic bioavailability is only 12% after a 300-mg dose. Among extensive metabolizers (greater than 90% of the United States population), bioavailability seems to vary nonlinearly with dose and increases substantially with food; these effects are not seen in poor metabolizers. Elimination is primarily hepatic, with a mean elimination half-life after oral administration of 5.5 hours in extensive metabolizers and 17.2 hours in poor metabolizers. The relationship between plasma propafenone concentration and clinical response varies considerably among individual patients; therefore, plasma concentrations have limited usefulness in predicting efficacy or electrophysiologic effects. Propafenone is effective in treating ventricular tachycardia and in suppressing premature ventricular complexes (PVCs). It is less effective in the treatment of refractory ventricular tachycardia. Concurrent administration of digoxin, warfarin, or metoprolol with propafenone has been shown to increase the serum concentrations of those three drugs, while cimetidine slightly increases the propafenone concentrations. Additive pharmacologic effect can occur when lidocaine, procainamide, and quinidine are combined with propafenone. Overall, 21% to 32% of patients experience adverse effects, with 3% to 7% of these serious enough to warrant discontinuing therapy. The most common adverse effects are dizziness or lightheadedness, metallic taste, and nausea and vomiting; the most serious adverse effects are proarrhythmic events.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1984

Propafenone disposition kinetics in cardiac arrhythmia.

Propafenone disposition kinetics were studied after intravenous and oral doses in patients with ventricular arrhythmias. Plasma concentration-time data were fit to a two-compartment model for all but one patient, whose data required fitting to a three-compartment model. The model-independent calculated values of clearance, steady-state volume of distribution, and terminal t1/2 were 11.2 +/- 4.8 ml/min/kg, 3.6 +/- 2.1 l/kg, and 5.0 +/- 3.6 hr. After 5 days on oral propafenone, elimination t1/2 was 6.2 +/- 3.3 hr. The longer t1/2s and the estimates of steady-state bioavailability above 100% suggests that clearance decreases during chronic oral dosing. Considerable intersubject variability was noted in all disposition parameters.

Adult↗