Lidocaine disposition in obesity.

Area of Science:

• Pharmacokinetics
• Obesity Research
• Clinical Pharmacology

Background:

• Lidocaine is a commonly used antiarrhythmic and local anesthetic.
• Body weight can influence drug pharmacokinetics, but its effect on lidocaine is not fully understood.
• Understanding how obesity affects lidocaine disposition is crucial for safe and effective dosing.

Purpose of the Study:

• To investigate the impact of obesity on the pharmacokinetic profile of lidocaine in men and women.
• To determine if obesity alters lidocaine's elimination half-life, clearance, and volume of distribution.
• To assess the relationship between body weight and lidocaine's pharmacokinetic parameters.

Main Methods:

• A single intravenous dose of 25 mg lidocaine was administered to obese and control men and women.
• Pharmacokinetic parameters including elimination half-life, clearance, and volume of distribution (Vd) were measured.
• Statistical analyses were performed to compare parameters between obese and control groups, and between sexes.

Main Results:

• Lidocaine's elimination half-life was significantly prolonged in obese men and women compared to their respective controls.
• This prolongation was attributed to an increased absolute volume of distribution (Vd) in obese individuals, not a change in clearance.
• Vd, when corrected for total body weight, remained unchanged, indicating Vd increases proportionally with body weight.

Conclusions:

• Obesity significantly alters lidocaine pharmacokinetics, primarily by increasing its volume of distribution.
• These findings suggest that standard lidocaine dosing may need adjustment in obese individuals to achieve therapeutic concentrations.
• The study implies that hepatic blood flow, a key determinant of lidocaine clearance, is not affected by extremes of body weight.