Transdermal fentanyl combined with nonsteroidal anti-inflammatory drugs for analgesia in horses. Thomasy SM(1), Slovis N, Maxwell LK, Kollias-Baker C. Author information: (1)K.L.ransdermal fentanyl combined with nonsteroidal anti-inflammatory drugs for analgesia in horses. Thomasy SM(1), Slovis N, Maxwell LK, Kollias-Baker C. Author information: (1)K.L.