Pharmacokinetics and preliminary safety evaluation of azithromycin in adult horses.

The research article is about a study that investigates the pharmacokinetics and preliminary safety of azithromycin, a drug commonly used in foals, in adult horses. The findings suggest that the drug’s characteristics make it compatible for use in adult horses but further studies are needed due to observed gastrointestinal alterations.

Study Design and Methodology

• The objective of this study was to understand the pharmacologic action and preliminary safety of azithromycin in adult horses. Azithromycin is a commonly used drug in foals, but its impact and efficacy had not been studied in adult horses prior to this.
• Azithromycin was administered to six healthy mares in two ways – through intravenous injection (5 mg/kg) and intragastric (10 mg/kg). The design was a crossover design, meaning the methods of administration alternated.
• To measure azithromycin concentrations, serial plasma samples were collected, as well as blood neutrophils and pulmonary macrophages. The drug was also orally administered (10 mg/kg) daily for 5 days to another five healthy mares to evaluate its safety in adult horses.

Study Findings

• The drug’s bioavailability following intragastric administration was found to be 45 ± 12%. Azithromycin concentrations were several times higher within peripheral neutrophils and bronchoalveolar macrophages compared to plasma.
• Some side effects such as decreased appetite and changes in fecal consistency were noted in three mares after repeated oral administration.
• The pharmacokinetic profile of azithromycin suggests that the drug’s slow elimination rate and its accumulation in neutrophils and pulmonary macrophages make it suitable for use in adult horses.

Study Implications

• While the study indicates that azithromycin can potentially be used in adult horses due to its pharmacokinetic profile, the gastrointestinal alterations noted warrants further research. Only after more extensive study can azithromycin be recommended for use in adult horses.
• The study opens up new avenues for treating diseases in adult horses using azithromycin. Future studies need to focus not just on the efficacy of the drug, but also its safety and long-term effects on the health of the horses.