Transdermal fentanyl combined with nonsteroidal anti-inflammatory drugs for analgesia in horses.

The research validates the effectiveness and safety of a fentanyl transdermal therapeutic system (TTS) coupled with nonsteroidal anti-inflammatory drugs for pain management in horses. This analgesic procedure was found to work well in horses that showed inadequate pain response to standard NSAID therapy.

Research Methodology

• The research included nine horses, each suffering from pain not adequately relieved by therapeutic doses of either phenylbutazone or flunixin meglumine.
• Each horse was subsequently given a dose of transdermal fentanyl, ranging between 39 and 110 micrograms per kilogram.
• Blood samples were collected from the horses at specific time intervals after the administration of fentanyl. The samples were drawn up to 72 hours post-application.
• These samples were then subjected to a radioimmunoassay to ascertain serum fentanyl concentrations. Pharmacokinetic values were then determined using a noncompartmental analysis technique.
• The research team also observed physical examination findings on all horses, assigning scores for pain and lameness in 8 and 6 horses, respectively.

Research Findings

• All horses tolerated the fentanyl TTS administration well, with no significant adverse effects linked to the application of fentanyl observed.
• The TTS led to variable serum concentrations of fentanyl, with an average peak serum concentration of 2.2±1.1 ng/mL and took about 26±13 hours to reach that peak.
• To reach the serum fentanyl concentrations associated with analgesia in other species (1 ng/mL), it took, on average, 14 hours post transdermal fentanyl administration. Except for one horse, all maintained this concentration level or more for at least 18 hours.
• Pain scores dramatically decreased after the administration of the fentanyl TTS and NSAID combination. However, there was no statistically significant difference in the lameness scores.

Research Conclusion

• Overall, the research concluded that the administration of a fentanyl TTS presents a favorable pharmacokinetic profile in horses dealing with clinical pain.
• This study suggests that a fentanyl TTS, when combined with NSAIDs, is an effective and safe method for analgesia in most horses unresponsive to pain using only NSAID therapy.