Serum amyloid A (SAA) is an acute phase protein produced in the liver that elevates within 24-48 hours and has a short half-life of about 24 hours. Intramuscular procaine penicillin G (PPG) is known to cause swelling, muscle pain, and procaine reactions following treatment. Flunixin meglumine (FM) provides inflammation-reducing effects.
At the 2023 AAEP Convention, Jurica Trsan, DVM, resident at the University of California, Davis, reported on a study she co-authored comparing the effects of intramuscular PPG alone, flunixin meglumine alone, and a combination of the two medications. The study’s objective was to determine if IM PPG elicits a sufficient inflammatory reaction that increases SAA in horses and if flunixin meglumine can ameliorate any SAA increase.
In the crossover study, Trsan’s team used six adult, mixed-gender, and aged-matched horses that served as their own controls. Each treatment period lasted three days, and the horses received four different treatments with a 30-day washout period in between. Different sides of the neck muscle were used for PPG administration; different jugulars were used for FM.
The results showed that individual SAA concentrations were within a normal reference range of ≤ 24 ug/ml for five out of six horses in each group—PPG, FM, combo, and control groups. The researchers found no statistical significance among the control and three treatment groups for changes in SAA.
PPG and FM Effect on SAA Response in Horses
In conclusion, Trsan noted that PPG and/or FM administered during elective procedures does not alter SAA kinetics, especially when administered in multiple sites over several days. Because elevated SAA post-elective procedure cannot be attributed to treatment with PPG and/or flunixin meglumine, treating veterinarians should consider another inflammatory source.