Pharmacokinetics of clarithromycin and concentrations in body fluids and bronchoalveolar cells of foals.

The research paper describes a study on the pharmacokinetics of clarithromycin in foals and its concentration level in various body fluids and bronchoalveolar (BAL) cells. The study provides insights into how the drug is absorbed, distributed, and eliminated in the body.

Methodology

• The study was conducted on six healthy foals aged between two to three weeks.
• The experimental design was a crossover in which, clarithromycin was administered to each foal via two routes – intravenously (IV) and intragastric (IG). The dosage used was 7.5 mg/kg.
• Following the first IG administration, additional doses were given IG at 12-hour intervals, five times.
• The concentrations of clarithromycin and its 14-hydroxy metabolite, which is the substance formed when the body processes clarithromycin, were measured in the serum using high-performance liquid chromatography, a technique used to identify, quantify and purify components of mixtures.
• A microbiological assay, or a test to measure the effects of a substance on a living organism, was used to measure the activity of clarithromycin in a variety of body fluids, including serum, urine, peritoneal fluid, synovial fluid, cerebrospinal fluid (CSF), pulmonary epithelial lining fluid (PELF) and BAL cells.

Results

• After IV administration of clarithromycin, the study determined the elimination half-life (time it takes for the concentration or amount of drug in the body to be reduced by one-half), body clearance rate, and the apparent volume of distribution at steady state.
• The metabolite of clarithromycin was detected in all foals within one hour of administering the drug, indicating that the substance was readily processed in the body.
• Oral bioavailability of clarithromycin, which refers to the extent and rate at which the active drug ingredient is absorbed and becomes available in the bloodstream, was found to be slightly over 57%.
• The maximum concentration of clarithromycin in the serum after multiple IG administrations was 0.88 +/- 0.19 micrograms/mL.
• Interestingly, after IG administration of multiple doses, the concentration of clarithromycin in peritoneal fluid, CSF and synovial fluid were comparable to or lower than that in the serum. However, the concentration in urine, PELF, and BAL cells were significantly higher than that in the serum.

Conclusions

• It was found that oral administration of clarithromycin at a dosage of 7.5 mg/kg every 12 hours maintained concentrations in serum, PELF, and BAL cells that are higher than the minimum inhibitory concentration for Rhodococcus equi isolates for the entire dosing interval. The minimum inhibitory concentration is the lowest concentration of a drug that prevents visible growth of a bacterium. This suggests that the dosage and administration method were effective in managing bacterial growth.