Pharmacokinetics of oral terbinafine in adult horses.

The research report discusses a study comparing the pharmacodynamics of oral terbinafine administered alone and with cimetidine in horses, also extending the study to its suspension form administered per rectum; the results reveal slightly different absorption rates, with minor side effects.

Objectives of the Study

• The study was primarily aimed at comparing the pharmacokinetics, or how the drug is absorbed, distributed, metabolized, and excreted, of oral terbinafine when given alone and with cimetidine in adult horses.
• The secondary aim was to study the pharmacokinetics of rectally administered terbinafine in two different suspensions at a dosage of 30mg/kg in adult horses.

Methodology Used

• The study was a crossover study involving six healthy horses.
• Plasma terbinafine concentrations were measured using a combination of liquid chromatography and mass spectrometry.

Key Findings

• The average half-life of terbinafine, when administered orally alone and with cimetidine, was approximately 8.38 and 10.76 hours respectively.
• Peak plasma concentrations of terbinafine occurred at 1.54 hours for solo oral administration and 1.28 hours when combined with cimetidine.
• When terbinafine was administered along with cimetidine, the concentration was around 44% higher than when administered alone, although this was not statistically significant.
• Terbinafine concentrations were seldom detected when administered rectally in two distinct suspensions (water or olive oil).
• Minor side effects noted in the study included oral irritation, fever, and colic, which were all self-resolving.

Implications and Recommendations

• There is a need for further pharmacokinetic studies, especially those focusing on drug-drug interactions. This would assist in improving understanding of effective oral dosing, potential for drug accumulation, and systemic adverse effects of terbinafine in horses.