Effect of feeding on the pharmacokinetics of oral minocycline in healthy adult horses.

The study investigates the influence of feeding on the effectiveness of minocycline, an antibiotic commonly used in horses to combat bacterial and rickettsial infections. Findings reveal that fasting horses prior to administering the drug increases its bioavailability and subsequently plasma concentrations, leading to improved efficacy.

Study Methodology

• The research was conducted using six healthy adult horses as subjects.
• The research methodology involved administering minocycline to these horses in two different scenarios – once with immediate access to hay (fed mode) and once with a 2-hour delay to hay after drug administration (fasted mode).
• A single dose of minocycline was given orally in both scenarios and the period between the two experimental treatments was 7 days, allowing for a washout between treatments.
• Additionally, an intravenous formulation of minocycline was administered in a dose of 2.2 mg/kg for comparison.
• The resulting plasma concentrations at various time intervals were studied and analyzed using noncompartmental pharmacokinetics, a method that quantitatively analyzes drug concentration versus time data without assuming any specific compartmental model.

Study Results and Conclusions

• The bioavailability (the proportion of the drug that enters the system and has an active effect) was measurably greater in fasted horses as compared to fed ones (38.6% ± 4.6 versus 15.7% ± 2.3).
• The average concentration of the drug (C) in the bloodstream was also higher in the fasted group (1.343 ± 0.418 μg/ml as compared to 0.281 ± 0.157 μg/ml in the fed group).
• This result indicates that the drug has a greater effect when administered after fasting, as a higher proportion of the oral dose is absorbed and utilized in the fasted state.
• The time taken to reach the maximum concentration (T) was not significantly different between the two groups.
• The conclusion drawn from these observations is that withholding feed prior to the administration of oral minocycline and delaying feeding for 2 hours post-administration improves the drug’s bioavailability and overall effectiveness in treating bacterial and rickettsial infections in horses.