Serum concentration of penicillin in the horse after repeated intramuscular injections of procaine penicillin G alone or in combination with benzathine penicillin and/or phenylbutazone.

The research article explores the impact of different dosage schedules and combinations of procaine penicillin G, benzathine penicillin , and phenylbutazone on the serum concentration of penicillin in horses.

Objective of the Study

• The main aim of this study was to understand how different combinations and dosages of three drugs (procaine penicillin G, benzathine penicillin, and phenylbutazone) affect the serum concentration of penicillin in horses. It also aimed to identify the dosage schedule that maintains an adequate serum penicillin concentration effective against penicillin-sensitive organisms.

Study Design and Sample

• 21 adult horses were involved in the study and were separated into 7 groups of three. The horses in each group were then subjected to different combinations and dosage schedules of the three drugs over a duration of 5 days.

Methodology

• The serum penicillin concentration in the horses was measured over a 7-day period, following the 5-day administration of the drug combinations.
• The peak values were observed between 2 to 4 hours after administering 22,000 IU/kg body weight of procaine penicillin G, given either once or twice daily.

Results

• The study found that the highest mean peak serum concentration of penicillin was 2.06 micrograms/ml.
• The research indicated that a minimum serum concentration of 0.25 micrograms/ml of penicillin was considered adequate to counter organisms sensitive to penicillin. This concentration was maintained by a once-daily administration of procaine penicillin G and some dosage schedules of procaine and benzathine penicillin G.
• The study also found that the concurrent administration of phenylbutazone did not significantly affect the serum concentration of penicillin.