Pharmacokinetics and pharmacodynamic effects of amiodarone in plasma of ponies after single intravenous administration.

This research paper investigates the effects of amiodarone, a drug used in human medicine for treatment of various heart arrhythmias, in ponies, specifically looking at its impact on ECG readings and pharmacokinetic parameters after single intravenous dose administration.

Objective of the Study

• The study aims to examine the impact of single intravenous doses of amiodarone on the electrocardiogram (ECG) of healthy minishetland ponies following drug administration. It also endeavors to calculate pharmacokinetic parameters using a physiologically based pharmacokinetic (PBPK) model with the help of amiodarone and desethylamiodarone plasma levels.

Methods and Techniques

• The experiment involves intravenous administration of amiodarone in two doses, 5 mg/kg and 7 mg/kg, to the ponies.
• Electrocardiograms are taken of the ponies over the two-day period post-administration to measure any potential changes.
• Bioanalysis of plasma samples to determine levels of amiodarone and desethylamiodarone, its metabolite, is performed using high-performance liquid chromatography (HPLC).
• Pharmacokinetic parameters are estimated using a physiologically based pharmacokinetic (PBPK) model using observed plasma levels.

Findings

• The ECG of the ponies post-administration showed statistically significant alterations in the QT interval and the T wave, an expected outcome for a drug that blocks potassium channels.
• The administered doses were generally well received from a clinical standpoint.
• The pharmacokinetic model suggested swift distribution of the drug in tissue, starting with rapidly perfused tissue like the heart, followed by slower perfused tissues, and finally a build-up in fat.
• The half-life for overall elimination was estimated at 16.3 days, with 99% of the drug expected to be eliminated by 97 days.
• The model predicts about 96% of amiodarone is excreted as desethylamiodarone in urine, 2% as desethylamiodarone in bile, and an additional 2% as other metabolites.