Ampicillin and its congener prodrugs in the horse.

The research article discusses the use of ampicillin, a common antibiotic, in horses, including challenges with conventional administration methods, attempts to prolong its effects, and alternate methods of administration such as the use of ampicillin prodrugs.

Ampicillin Properties and Administration Challenges

• The use of ampicillin in horses is common, typically administered intravenously (i.v.) or intramuscularly (i.m.).
• Ampicillin’s physicochemical properties, however, make it hard to absorb when administered orally, leading to its quick elimination from the body.
• This study examined methods to prolong the effects of ampicillin in horses by modifying its rates of elimination from and absorption into the body.

Attempts to Alter Ampicillin Elimination and Absorption

• The researchers attempted to change the urinary pH but found out that it did not affect the plasma disposition of the antibiotic.
• However, administering the drug probenecid concurrently with ampicillin significantly reduced the overall clearance of the antibiotic from the body, thus extending its effects.

Use of Intravenous Infusion

• The administration of ampicillin as an i.v. infusion can also maintain the antibiotic in a horse’s body for an extended period.
• The practical difficulties associated with this method, in addition to limited potential benefits over conventional administration methods such as i.m. injection, limit its application to critically ill animals or during the perioperative period.

Use of Ampicillin Prodrugs

• The study explored the use of ampicillin prodrugs bacampicillin and pivampicillin.
• When administered to horses, these prodrugs showed high oral bioavailability, indicating its successful absorption when administered orally.
• This development suggests the need for further research into the use of prodrugs as a potential method of ampicillin administration.

Future Use of Ampicillin

• The increasing emergence of antibiotic-resistant bacterial strains in horses may limit the future use of ampicillin.
• To mitigate this issue, the researchers suggested limiting the use of ampicillin following good clinical pharmacological practice principles.