Intramuscular administration of sodium benzylpenicillin in horses as an alternative to procaine benzylpenicillin.

The research investigates the use of sodium benzylpenicillin, instead of procaine benzylpenicillin, for treating horses, looking at its effectiveness and potential side effects. However, while this treatment seemed to work well in killing bacteria, it caused more pain and swelling in the horses compared to the control treatment.

Objective of the Study

• The researchers aimed to examine the feasibility and impact of replacing procaine benzylpenicillin with sodium benzylpenicillin salt for intramuscular treatment in horses. The intent behind considering this alternative was lessening the risk of procaine-related side effects in the animals.

Design and Methodology

• In a crossover study conducted on eight horses, the researchers administered 15 mg/kg of sodium benzylpenicillin twice a day, while a control group was given procaine benzylpenicillin once daily via intramuscular injection, continued for four days.

Findings of the Study

• The sodium salt (Na-pc) of benzylpenicillin had a half-life of 1.9 hours and achieved a peak concentration of 14,600 ng/mL after approximately 23 minutes post-administration. The end, or trough, plasma concentration was found to be 281 ng/mL, and 62.8% of the drug was bound to proteins.
• The fractional time above the Minimum Inhibitory Concentration (fT>MIC), which refers to the period for which drug levels remain above the minimum required to inhibit bacterial growth, was 63% for Staphylococcus aureus (a common bacteria which can cause a variety of diseases in animals and humans). It was found to be 100% for both Streptococcus equi subsp. equi and Streptococcus zooepidemicus bacteria, which are responsible for various equine diseases. This implies that sodium benzylpenicillin was effectively able to provide adequate antimicrobial therapy.

Conclusion of the Study

• Despite the effective antimicrobial action of sodium benzylpenicillin, the researchers concluded that it cannot be universally recommended for intramuscular treatment in horses. During the study, consistent patterns of increased pain-related behaviors were observed in the horses that were given sodium benzylpenicillin compared to those that received the control treatment of procaine benzylpenicillin. Additionally, these horses showed more significant pain and swelling, indicating increased discomfort and reduced animal welfare.