Tramadol Effects on Lameness Score After Inhibition of P-GP by Ivermectin Administration in Horses: Preliminary Results.

The research article evaluates the impact of tramadol administration on horses’ lameness, particularly after using P-glycoprotein (P-gp) inhibitor ivermectin, with the findings suggesting that the interaction doesn’t significantly alter tramadol’s effects.

Background and Methodology

• The study was designed to analyze the effects and assess the degree of lameness in horses given tramadol after administering P-gp inhibitor ivermectin. This P-glycoprotein is a protein molecule which acts as a transporter, evacuating drugs and other kinds of toxins from cells.
• For this research, six horses were selected randomly and divided into three groups. Each group received two unique doses of tramadol through a nasogastric tube: one group received 1mg/kg (labeled as GT1), the second group received 4mg/kg (labelled as GT4), and the third group received 1mg/kg tramadol combined with 0.2mg/kg ivermectin (labelled as GT1 + Ive).
• The doses were administered with a one-week wash-out interval – a period where horses received no treatment – for the purging of any drug effects from their system.
• Several vital signs and parameters were measured over a period of 360 minutes, like Heart Rate (HR), Respiratory Rate (RR), intestinal motility, body temperature, and lameness degree. Blood gas parameters, vital for understanding the amount of oxygen and carbon dioxide in the blood, were evaluated at the 0, 60, and 120 minute marks.

Results and Conclusion

• The findings indicated that there were no differences in both HR and the degree of lameness among the groups.
• Hypomotility (decreased motor function) was observed in GT1 and GT4 towards the end of the observation period, indicating that tramadol may have some delayed impacts on these parameters.
• The RR increased across all groups, which could be a common response to tramadol regardless of whether it was given with or without ivermectin.
• The research suggests that inhibition of enteric P-gp by ivermectin did not alter tramadol’s effects, which could mean that tramadol is not a substrate for P-gp. In other words, tramadol does not appear to rely on P-GP for its transport or metabolism.
• However, the authors conclude that more studies will be required to further assess the interaction between P-gp inhibitors and the pharmacokinetics (how a body reacts to a drug) of tramadol.