Intranasal administration of Fentanyl in dogs for the treatment of severe post-operative pain

Aim of this study was to assess in dogs the analgesic effects of intranasal (IN) administration of fentanyl citrate for the treatment of severe post-operative pain. N. 8 privately owned dogs of different breeds and sex, 2,69±2,8 years and 19,45±14,08 kg, undergone routine orthopedic procedures or laminectomy under isoflurane anesthesia, were randomly enrolled in the study under owner consent. After recovery, the dogs were hospitalized for the treatment of intense post- operative pain. Pain score (PS) was measured every 5 minutes starting from extubation by a modified multiparametric algometric scale (University of Melbourne Pain Scale) (1). When PS exceeded 6/23 (severe pain) 4 ??g/kg of fentanyl citrate (Fentanest® Pfizer Italia S.r.l., 0.1mg/2ml) were administered by intranasal route by a nasal Mucosal Atomization Device (MAD® Wolfe Tory Medical Inc., Salt Lake City, UT, USA). Analgesic effect onset and duration were noted and vital parameters (T°C, RR, HR, NIBP and SPO2) were continuously recorded by a multiparametric monitor (Mindray PM-9000 Express®) before (T0) and up to 60 minutes after IN fentanyl administration. Analgesic treatment was continued by IM buprenorphine (20 ??g/kg) according to patient needs. Physiological parameters and PS were reported at 5 minutes intervals (T0-T60) on an Excel sheet and processed by Analysis of Variance for repeated measures (ANOVA). When a significant difference was identified post hoc Tukey???s (P??? 0,05) was applied. Intranasal administration of fentanyl citrate effectively reduced severe pain in our patients showing an onset time of 9,38±4,17 minutes, reaching a peak analgesic effect in about 20 minutes (PS median=3,5) and an overall duration of 35,63±8,21 minutes. PS showed significant differences during the observation interval (P<0,0001) identified between time points: T50>T15; T55>T20; T60>T20; T60>T15. No significant differences in T°C, RR, HR, NIBP and SPO2 were recorded. No adverse effects were observed in any subject. This study substantiates the IN administration of fentanyl for the treatment of severe postoperative pain in dogs as a suitable alternative to standard IV route and other analgesic treatments commonly used in the intensive care unit, due to the short latency and the full analgesic effect observed. Intranasal administration of opioids is commonly used in humans, especially in case of severe and sudden pain due to its rapid absorption and clinical effectiveness (2). A new fentanyl citrate formulation is now marketed for the treatment of breakthrough pain in human cancer patients for its rapid onset and ability to bypass first pass metabolism (2; 3). (1) Ava M. F. and Sarah L.H. JAVMA 1999 Mar, vol 214: 651-659 (2) Grassin-Delyle et al. Pharmacology & Terapeutics 2012, 134: 366-379 (3) Ruediger Nave et al. Drug Deliv, 2013; 20(5): 216-223