title: The effect of transdermal delivery of fentanyl on activity in growing pigs.
abstract: Recently, decreased activity levels have been observed in pigs treated postoperatively with transdermal delivery of fentanyl (TD-fentanyl) after isoflurane anaesthesia. Whether the change in behaviour is related to opioid-induced sedation or to insufficient pain relief remains to be investigated. This study was therefore undertaken to evaluate the effect of TD-fentanyl 50 microg h(-1) on the activity level with and without isoflurane anaesthesia. Eight pigs (25.4 +/- 5.2 kg) were submitted to a cross-over study and given two treatments; 1) fentanyl patch applied after 30 minutes of anaesthesia (treatment A/F) and 2) fentanyl patch without anaesthesia (treatment F). The pigs' behaviour was observed from a video recording instantaneously every 10 minutes for 24 h before treatments and up to 72 h after the patch attachment. Venous blood samples were taken 1, 6, 12, 24, 48 and 72 h after the patch application. The behaviour recordings showed that TD-fentanyl did not produce sedation in any pig. No differences were found between the two treatments in activity level, weight gain or serum fentanyl concentration. This concentration measured after 24 h was 0.27 +/- 0.11 ng ml(-1) and 0.47 +/- 0.40 ng ml(-1) in the A/F and F group, respectively. In conclusion, transdermal delivery of 50 microg h(-1) fentanyl did not cause inactivity in growing pigs. However, the large variations in serum fentanyl concentration indicate that drug absorption from transdermal patches is unpredictable and sometimes deficient.
authors.affiliation: Department of Clinical Sciences, Faculty of Veterinary Medicine and Animal Science, Swedish University of Agricultural Sciences, Uppsala, Sweden. Lais.Malavasi@kv.slu.se
authors.forename: L M
authors.initials: LM
authors.lastname: Malavasi
authors.forename: H
authors.initials: H
authors.lastname: Augustsson
authors.forename: M
authors.initials: M
authors.lastname: Jensen-Waern
authors.forename: G
authors.initials: G
authors.lastname: Nyman
mesh_terms: D000279:Administration, Cutaneous; D000701:Analgesics, Opioid / Q000008:administration & dosage* / Q000097:blood / Q000378:metabolism; D018685:Anesthetics, Inhalation / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D002849:Chromatography, Gas / Q000662:veterinary; D018592:Cross-Over Studies; D005260:Female; D005283:Fentanyl / Q000008:administration & dosage* / Q000097:blood / Q000378:metabolism; D007530:Isoflurane / Q000494:pharmacology; D008137:Longitudinal Studies; D013552:Swine / Q000254:growth & development*; D014741:Video Recording
chemical_list: D000701:Analgesics, Opioid; D018685:Anesthetics, Inhalation; D007530:Isoflurane; D005283:Fentanyl