Effect of Procaine Penicillin G and Flunixin Meglumine on Serum Amyloid A Response in Healthy Adult Horses.
Authors: Trsan Jurica, Nottle Bridget F, Pusterla Nicola
Journal: Journal of equine veterinary science
Summary
# Editorial Summary Serum amyloid A (SAA) is a key acute phase protein used clinically to assess systemic inflammation in horses, yet uncertainty persists about whether commonly prescribed antimicrobials and anti-inflammatories themselves provoke measurable SAA elevation in healthy animals. Trsan *et al.* (2023) investigated this question using a crossover design in six horses, comparing control conditions against three treatment regimens: procaine penicillin G (PPG) alone, flunixin meglumine alone, and the combination, with SAA measurement at six timepoints over five days. Neither drug administered at standard clinical dosages induced significant SAA elevation; whilst one horse in the combined treatment group did show transient SAA values of 32–45 µg/mL between 48–96 hours (compared to the normal threshold of ≤20 µg/mL), the area under the SAA time curve showed no statistical difference between treatment and control groups. For equine practitioners, this finding is reassuring: SAA elevation detected during or immediately following routine PPG or flunixin therapy in a clinically healthy horse should not be reflexively attributed to the medications themselves, suggesting any such rise warrants investigation for underlying infection or inflammatory disease rather than being dismissed as a drug artefact.
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Practical Takeaways
- •Clinical dosing of procaine penicillin G and/or flunixin meglumine at standard regimens does not induce measurable systemic inflammation in healthy horses, making these drugs safe for routine therapeutic use
- •When either or both drugs are used at clinical doses, expect SAA values to remain within normal range (≤20 µg/mL) in most cases, reducing concern about drug-induced inflammatory reactions
- •If elevated SAA is observed in a treated horse, it is likely due to an underlying condition rather than the medications themselves
Key Findings
- •Procaine penicillin G alone did not trigger elevated serum amyloid A (SAA) in any horse during the 120-hour study period
- •Flunixin meglumine alone resulted in normal SAA values in all but one horse (24 µg/mL at 96 hours)
- •Combined PPG and flunixin meglumine therapy resulted in elevated SAA (32-45 µg/mL) in only 1 of 6 horses between 48-96 hours
- •No statistically significant difference in area under the SAA time curve between control and all three treatment groups (P > 0.05)