Pharmacokinetics of bacampicillin in equids.

This research investigates the pharmacokinetics of an antibiotic medicine named bacampicillin in horses and ponies. The study measures how the drug is absorbed, distributed, metabolised and excreted in these animals.

Study Methodology

• The researchers administered bacampicillin hydrochloride, an ester prodrug, intragastrically to ponies and horses.
• The dosage given was 13.5 mg/kg of body weight. A prodrug is a substance that, once ingested, is metabolised into a pharmacologically active drug – in this case, ampicillin.
• In another experiment, an organophosphate compound called dichlorvos, known for inhibiting some of the esterase activity in plasma, was orally given to the animals, followed by bacampicillin. The dosage was 40 mg/kg for dichlorvos and 13.5 mg/kg for bacampicillin respectively.
• The researchers also experimented with coadministering probenecid (at a dose of 75 mg/kg) and bacampicillin (at 13.5 mg/kg). This was to test a theory about a potential common transport mechanism in the equids’ gastrointestinal wall for these two substances.

Key Findings

• The bioavailability of bacampicillin was found to be high (41.0%), compared to other penicillins used in horses, indicating that it is highly absorbed and utilised by the body.
• A high peak concentration of the active antibiotic, ampicillin, in the plasma was recorded, indicating that it may reach suitable bactericidal concentrations for treatment of infections caused by susceptible microorganisms.
• Despite the esterase-inhibiting actions of dichlorvos, its administration didn’t affect the production of ampicillin from bacampicillin, i.e., the rate of hydrolysis was unaffected.
• The experiment with probenecid demonstrated that it limited the absorption of bacampicillin, suggesting a common transport mechanism for both in the gastrointestinal wall. This limits the potential for concurrent use of these two substances for treatment.

Implications of the Study

• The high bioavailability of bacampicillin might make it a better choice for treating certain types of infections in equids.
• Even though dichlorvos limits some plasma esterase activity, this doesn’t affect bacampicillin’s ability to be metabolised into ampicillin.
• The interference of probenecid in the absorption of bacampicillin is significant as it suggests that the two drugs cannot be co-administered for effective treatment.

This research adds valuable understanding regarding bacampicillin’s pharmacokinetics in horses and ponies, providing information that could be used to refine treatment strategies using this antibiotic.