Pharmacokinetics of danofloxacin in horses after intravenous, intramuscular and intragastric administration.

This research looks at the absorption and effect of the antibiotic danofloxacin in horses through different administration methods, namely intravenous (IV), intramuscular (IM) and intragastric (IG). The results suggest that injecting danofloxacin either intravenously or intramuscularly is more effective in treating bacterial infections in horses than administering it orally through the stomach.

Study Design and Methodology

• The research was conducted using a cross-over design, which typically involves participants receiving multiple treatments in a randomized order over time. The same group of six healthy horses was administered danofloxacin in three separate phases, each time through a different route.
• The pharmaceutical was administered at a dosage of 1.25 milligrams per kilogram of horse body weight, with a 15-day ‘washout’ period in between different methods of administration to eliminate any residual effects of the drug.
• The researchers used High-Performance Liquid Chromatography (HPLC) with fluorescence detection to measure the concentration of danofloxacin in the horse’s plasma over time. This helped them understand how rapidly the drug is absorbed, distributed, metabolized, and eventually excreted by the body.
• They also monitored creatine kinase (CK) activity at the site of intramuscular injections as an indication of any muscle damage or irritation caused by the drug administration.

Study Findings

• The pharmacokinetic data obtained showed that danofloxacin present in horse’s blood after intravenous and intragastric administration followed a two-compartment open model, while intramuscular administration followed a one-compartment model. This shows differences in the way the drug was metabolized and distributed in the body based on its mode of administration.
• The results showed that the drug was most effective when administered either via intravenous or intramuscular injection, due to its higher bioavailability – the proportion of the drug that entered circulation and was able to have an active effect. IV and IM administration had bioavailabilities of nearly 89% and over 22% respectively.
• However, the researchers observed that the creatine kinase (CK) activity level, an indicator of muscle damage, increased three-fold above normal 12 hours after intramuscular administration, implying a slight discomfort or damage, though it did reduce approaching normal values by the 72nd hour post-administration.

Conclusion

• Given the pharmacokinetics and blood levels achieved through intravenous and intramuscular administration routes, coupled with their higher bioavailability and tolerability, danofloxacin is likely to be effective for treating bacterial infections in horses when administered through these routes.
• The study also points out that despite the convenience of oral administration, the intragastric route had limited efficacy, owing to its relatively low bioavailability.