Plasma disposition of enrofloxacin following intravenous and intramuscular administration in donkeys.

The research article summarises an experiment on how donkeys (Equus asinus) metabolise the drug enrofloxacin (ENR) when administered intravenously (directly into the bloodstream) versus intramuscularly (into the muscle tissue). The study found that ENR stays in a donkey’s system longer when given intramuscularly, and the body absorbs nearly 77% of the drug in this form, which may suggest a need for a higher dose compared to its use in horses.

Study Design and Procedure

• The study involved six donkeys divided into two groups. Each group was administered ENR either intravenously or intramuscularly, and then the groups were switched after a 2-week washout period (time allowed for the drug to be completely cleared from their bodies). This is known as a two-phase crossover design.
• The dose of ENR administered in both cases was 5 mg/kg of the donkey’s body weight.
• Before and after the drug administration, blood samples were collected from the donkeys at various time intervals up to 48 hours.
• Analysis of these blood samples was done using high-performance liquid chromatography with a fluorescence detector, a reliable method for detecting the presence and concentration of specific substances in a fluid.

Results and Observations

• The average time for ENR to remain in the body (mean residence time) and the time by which the drug reduces to half its initial concentration (half-life) was found to be longer when administered intramuscularly than intravenously. This occurrence, known as the flip-flop phenomenon, suggests that the drug’s absorption rate outperformed its elimination rate following intramuscular administration.
• It was observed that a considerable proportion (20-21%) of the administered ENR was metabolised into another drug – ciprofloxacin (CPR). The half-life of CPR paralleled the half-life of the parent drug (ENR) post intramuscular administration.
• Mean absorption time was relatively long (10.39 hours), and the systemic availability or bioavailability (percentage of the administered drug that enters the body’s bloodstream and is available at the site of action) of ENR was calculated to be 76.56% after intramuscular administration.
• Based on the plasma concentration level after intramuscular administration, the researchers suggested that it may require a higher dose of ENR administered intramuscularly (as compared to the intravenous route) to provide a sufficient concentration of the drug in the bloodstream of donkeys, than in horses.

These findings could significantly impact the dosage and method of administering ENR in veterinary settings for better efficacy and patient safety. Further research is recommended to establish the optimal dosage and administration route for ENR in donkeys as compared to other animals like horses.