Disposition of oral clarithromycin in foals.

The research explored the effectiveness of an antibiotic, clarithromycin, in treating Rhodococcus equi infections in foals, observing its presence in their systems after oral intake and suggesting an appropriate dosage for therapeutic purposes.

Overview of the Research

• This study by the authors was undertaken to examine and understand the breakdown or disposition of the antibiotic clarithromycin in foals – baby horses.
• The need arose from the known benefits of clarithromycin over another antibiotic, erythromycin, in treating infections caused by Rhodococcus equi, a bacteria often found in livestock conditions.
• The researchers administered an oral dosage of clarithromycin to six foals and then mapped out its presence in their systems over a certain duration.

Administration of Clarithromycin and Initial Observations

• The foals were given clarithromycin at a dosage of 10 mg per kg of their body weight through intragastric administration, a method involving delivering the drug straight to the stomach.
• The presence of the drug was initially checked at 10 and 20 minutes after administration. While only three of the six foals had detectable levels of clarithromycin at 10 minutes, all six showed presence of the antibiotic in their serum by the 20-minute mark.

Measuring Clarithromycin Concentration Over Time

• The scientists then observed and recorded the changes in serum concentration of the drug over time. The peak serum concentration (Cmax) was noted as 0.92+/-0.17 micrograms per milliliter and the time taken to reach this peak (Tmax) was 1.5 hours.
• These concentrations then gradually began to decline over the course of 24 hours, reaching a mean value of 0.03 micrograms per milliliter at the end of this period.

Safety and Proposed Dosage of Clarithromycin

• Throughout the duration of the study, none of the foals showed any adverse reactions to the oral administration of clarithromycin.
• Taking into account the calculated pharmacokinetic parameters (the behavior of the drug in the foals’ bodies), the MIC90 of Rhodococcus equi isolates (the minimum inhibitory concentration needed to inhibit the growth of 90% of organisms), and predicted steady-state concentrations of the drug, the researchers concluded that an oral dose of 7.5 mg per kg body weight of clarithromycin every 12 hours appears to be an effective treatment dosage for Rhodococcus equi infections in foals.