Evaluation of a transdermal fentanyl system in yucatan miniature pigs

Of 18 pigs used on a coronary stent experimental protocol, 6 each received a transdermal fentanyl patch to document the patterns of transdermal fentanyl absorption in swine. This approach was taken to reduce animal use and potentially refine the surgical regimen. The objective of the fentanyl portion of the study was to demonstrate that transdermal fentanyl may be useful in the management of postoperative analgesia in swine. This study sought to document that demonstrable levels of fentanyl are achievable in swine plasma via a transdermal system and to compare the magnitude of these levels to data in other species. This study does not directly correlate plasma fentanyl levels with analgesic efficacy. Plasma fentanyl concentration peaked within 42 h in five pigs and within 48 h in the remaining pig. All pigs had similar absorption patterns; the only difference was in magnitude. One pig reached 0.99 ng/ml at 42 h; the next highest concentration was 0.77 ng/ml at 48 h in a different animal. The peak concentration in the others ranged from 0.38 to 0.71 ng/ml.