Phenoxymethyl penicillin in the horse: an alternative to parenteral administration of penicillin.

This study explored the use of oral administration of phenoxymethyl penicillin (Penicillin V) in horses as an alternate approach to injectable penicillin. The results showed that oral Penicillin V can maintain effective plasma drug levels, making it a viable alternative to traditional penicillin injections.

Objective and Methodology

• The preliminary study aimed to assess whether phenoxymethyl penicillin, also known as Penicillin V, could serve as an alternative to the parenteral (or injected) administration of penicillin in horses.
• Five horses took part in the study, and Penicillin V was administered orally at two distinct dosage levels. Subsequently, plasma levels of the drug were measured at timed intervals and evaluated through regression analysis.

Findings

• The study found that following the administration of Penicillin V at dosages of 66,000 IU/kg and 110,000 IU/kg, the average peak plasma levels were found to be 1.55 micrograms/mL and 2.34 micrograms/mL respectively.
• A plasma level two to four times higher than the minimum inhibitory concentration (MIC) level of the bacteria Streptococcus equi and Streptococcus zooepidemicus was maintained for at least 325 minutes when administered 66,000 IU/kg and for about 349 minutes when given 110,000 IU/kg.

Conclusion

• The results from this study demonstrate that oral administration of Penicillin V can be an efficient alternative to parenteral administration of penicillin in horses. This is due to the ability of the oral variant to sustain plasma levels of the drug at a high enough concentration to inhibit the growth of harmful bacteria for a considerable amount of time.
• These findings could have practical implications for the equine industry by offering a less invasive method of medication administration, potentially enhancing horse welfare by reducing the stress associated with injections.