Pharmacokinetics and distribution of minocycline in mature horses after oral administration of multiple doses and comparison with minimum inhibitory concentrations.

The research conducts an investigation into the pharmacokinetics, safety, and penetration of minocycline in horses following oral administration over multiple doses. The study supports the use of oral minocycline for treatment of non-ocular infections in horses, yet highlights the necessity for further research to establish effective dosing for the treatment of ocular infections.

Study Objective and Methods

• The objective of this study was to uncover the pharmacokinetics, safety, and penetration of minocycline into different body fluids like plasma, synovial fluid, aqueous humour, and cerebral spinal fluid in horses upon oral administration.
• The study involved administering six horses with oral minocycline in doses of 4 mg/kg bodyweight every 12 hours over five doses.
• Researchers collected thirty-three blood and nine synovial fluid samples over a period of 96 hours, and aqueous humour and CSF samples were collected an hour after the final dose.

Measurement and Analysis

• Using high-pressure liquid chromatography, minocycline concentrations in various samples were identified and measured.
• The study also determined the minimum inhibitory concentrations (MIC) for minocycline against equine pathogenic bacteria with 301 bacterial isolates used to determine the MIC values.

Result Report

• The peak concentration of minocycline in the plasma was 0.67 ± 0.26 µg/ml, while the mean half-life was around 11.48 hours.
• The highest trough synovial fluid minocycline concentration was 0.33 ± 0.12 µg/ml, and it was present at levels of 0.09 ± 0.03 µg/ml in normal eyes’ aqueous humour and 0.11 ± 0.04 µg/ml in blood aqueous barrier-disrupted eyes.
• The mean CSF concentration of minocycline was 0.38 ± 0.09 µg/ml.
• Minocycline concentrations were observed to be greater than MIC(50) and MIC(90) for numerous gram-positive equine pathogens.

Conclusions and Implications

• The study supports the use of orally administered minocycline at a dosage of 4 mg/kg bodyweight every 12 hours for treating nonocular infections in horses due to susceptible (MIC ≤ 0.25 µg/ml) organisms.
• Nonetheless, more research is needed to determine the efficient dose for treatment of minocycline in ocular infections.