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Pharmacokinetic implications of lorcainide therapy in patients with normal and depressed cardiac function
P Somani1, T D Fraker, P N Temesy-Armos
1Department of Medicine, Medical College of Ohio, Toledo 43699.
Insights
Left ventricular ejection fraction did not significantly alter lorcainide pharmacokinetics in cardiac patients. Therapeutic antiarrhythmic effects correlate with plasma lorcainide concentration, necessitating monitoring.
Area of Science:
- Pharmacology
- Cardiology
- Clinical Pharmacy
Background:
- Assessing antiarrhythmic drug efficacy requires understanding pharmacokinetic variability.
- Left ventricular ejection fraction (LVEF) is a key indicator of cardiac function.
- Lorcainide is a novel antiarrhythmic agent with potential for variable patient response.
Observation:
- Twenty cardiac patients were stratified by LVEF (normal >.40 vs. depressed <.40).
- Pharmacokinetic variables (half-life, clearance, volume of distribution) of lorcainide were analyzed.
- No significant pharmacokinetic differences were observed between normal and depressed LVEF groups.
Findings:
- Antiarrhythmic effect of lorcainide correlated with plasma drug concentrations.
- A minimum plasma concentration of 0.1 mg/L was required for antiarrhythmic effect.
- Significant interpatient variability (3- to 6-fold) in lorcainide elimination half-life exists.
Implications:
- Individualized monitoring of plasma lorcainide concentrations is crucial for efficacy and safety.
- Understanding pharmacokinetic variability is essential for optimizing lorcainide dosing.
- Therapeutic drug monitoring can minimize adverse events and maximize antiarrhythmic response.
Abstract:
The influence of cardiac function as measured by the left ventricular ejection fraction on the pharmacokinetic variables of a new antiarrhythmic drug, lorcainide, was investigated in 20 cardiac patients. Patients were divided into two groups: those with normal (ejection fraction greater than .40) or depressed (ejection fraction less than .40) left ventricular function. The elimination half-life, plasma clearance rates, or volume of distribution of lorcainide were not significantly different in patients with either normal or depressed cardiac function. A decrease in arrhythmia frequency could be correlated to plasma lorcainide concentration in the majority of patients, and it was noted that at least 0.1 mg/L of lorcainide was required for the presence of an antiarrhythmic effect. Three unusual cases are presented to illustrate the importance of measuring plasma drug concentrations and calculating the drug pharmacokinetics and to correlate these to the antiarrhythmic response in order to minimize the risk of plasma drug accumulation and side effects. A review of published data shows a three- to sixfold interpatient variation in the elimination half-life of lorcainide with practical implications in its use as an antiarrhythmic drug.