Disopyramide elimination in the isolated perfused rat liver

Area of Science:

• Pharmacokinetics and Drug Metabolism
• Hepatobiliary Transport

Background:

• Disopyramide is an antiarrhythmic drug with complex elimination pathways.
• Understanding its hepatic metabolism and excretion is crucial for optimizing therapeutic use.

Purpose of the Study:

• To investigate the elimination kinetics of disopyramide and its metabolites in an isolated perfused rat liver model.
• To elucidate the rate-limiting steps in disopyramide clearance and identify potential saturation mechanisms.

Main Methods:

• Utilized an isolated perfused rat liver system to study disopyramide elimination.
• Administered varying doses of disopyramide, including radiolabeled ([14C] and [2H]) forms, to assess dose- and time-dependency.
• Monitored disopyramide disappearance from the perfusate and quantified radioactivity.

Main Results:

• Disopyramide disappearance from the perfusate was dose- and time-dependent across a 0.3-7.5 mg dose range.
• Data suggest enzyme saturation and product inhibition as potential mechanisms influencing elimination.
• Biliary secretion of conjugated metabolites was identified as the rate-limiting step for total radioactivity clearance.
• A minor isotope effect was observed with [2H]disopyramide, deemed negligible in importance.

Conclusions:

• The elimination of disopyramide in the perfused rat liver is subject to saturable processes.
• Hepatobiliary excretion of disopyramide metabolites is a key determinant of overall drug clearance.
• The findings provide insights into the pharmacokinetic behavior of disopyramide, relevant for its clinical application.