Preliminary investigation of concurrent administration of phenylbutazone and romifidine in healthy horses.

The research article investigates the effects of co-administering two drugs, phenylbutazone and romifidine, on the cardiorespiratory system and electrocardiograms of healthy horses through a blinded, randomized, and cross-over trial.

Methodology

• The preliminary study utilized a prospective four-period, four-treatment, blinded, randomized, crossover trial method. This means that the participants (in this case, five healthy mixed breed horses) received each treatment in a random order, with each treatment separated by a washout period of at least one week to allow any effects of the previous treatment to wear off.
• The administration of treatment was performed using intravenous injection. The treatment groups included a saline placebo (intended as a control), phenylbutazone alone, romifidine alone, and a combination of phenylbutazone and romifidine.
• Before administering the drugs, the researchers inserted a catheter into the horses’ cranial vena cava through the jugular vein. A carotid artery was also catheterised using subcutaneous access (under the skin).
• To monitor physiological responses, several parameters were recorded, including heart rate, respiratory rate, systolic (SAP), diastolic (DAP) and mean (MAP) arterial pressures, and central venous pressure (CVP). These records were taken before drug administration (baseline) and at 5-minute intervals for 30 minutes post-administration. Any abnormalities in the electrocardiogram were also reported.

Results

• The results showed no statistically significant differences in the cardiovascular parameters between horses treated with romifidine only and those treated with a combination of phenylbutazone and romifidine.
• Statistically significant differences were found between those treatments including romifidine (be it alone or in combination) and those not containing romifidine (the control and phenylbutazone alone).
• Over time, significant changes were observed in heart rate, arterial pressures, and central venous pressure for the romifidine group, and in central venous pressure for the combined group.
• Sino-atrial and atrio-ventricular blockages (certain types of heart rhythm issues) were observed in horses treated with romifidine alone and the combined treatment.

Conclusion

• The experiment concluded that no significant effects on cardiorespiratory variables were observed when phenylbutazone and romifidine were administered together, compared to when administered separately.
• The researchers stated that their findings don’t offer any reasons why these two drugs shouldn’t be used together in preoperative medication for healthy horses, although they caution that these results may not apply to a larger population, or the possibility of interactions can’t be entirely excluded.