The pharmacology of furosemide in the horse. V. Pharmacokinetics and blood levels of furosemide after intravenous administration.

This research article explores how the drug furosemide acts in horses’ bodies, focusing particularly on how it’s distributed in the blood after being administered intravenously. It was found that the drug behaves in a dose-independent manner and the distribution characteristics best match a three-compartment open model.

Objective of the Study

• The main objective of this research was to understand the pharmacokinetics and blood levels of furosemide in horses after administration by intravenous (iv) injection. The doses examined were 0.5 and 1.0 mg/kg.

Method and Findings

• The researchers analysed the pharmacokinetic parameters and found them to be dose-independent, meaning that the drug’s behavior in the body didn’t significantly change with the varied doses.
• The disposition of the furosemide was found to best fit a three-compartment open model, which is a mathematical model used to describe how a drug is absorbed, distributed, metabolized, and excreted.
• The study found that the half-lives (the time taken for the drug’s concentration to halve) in three phases (alpha, beta, and gamma) were 5.6, 22.3, and 158.5 minutes respectively for the smaller dose, and slightly longer for the larger dose.
• The investigation also looked into the distribution of furosemide in a population of horses following drug administration. They analysed the blood levels at two different time intervals; 1 hour and 4 hours after administering the drug.
• At 1 hour after dosing, the drug levels were normally distributed across the population, with an average plasma level of 97.9 ng/ml. At 4 hours after dosing, the average concentration dropped to 9.6 ng/ml and a log transformation of the values resulted in a better fit to a normal distribution curve.

Conclusion and Implications

• This research concluded that the behavior of furosemide in horses can be best understood using a three-compartment open model, and that its pharmacokinetic parameters are dose-independent.
• The findings also provide knowledge about the duration of therapeutic levels of furosemide remaining in the bloodstream post-administration, which can aid in determining optimal dosing schedules.
• This information is important for veterinary medicine as furosemide is commonly used in horses for conditions like exercise induced pulmonary haemorrhage. Understanding the pharmacokinetics of this drug can assist in improving the drug administration practices and optimize therapeutic efficacy.