A Critical Review of the Pharmacokinetics and Pharmacodynamics of Opioid Medications Used in Avian Patients

Evelyn Aliansyah,Hui Ting Chng,Shangzhe Xie

doi:10.3390/birds3010001

Abstract

Opioid drugs are used to manage moderate to severe pain in mammals and avian species. In dosing opioids for a particular species, it is optimal to use dosing regimens based on pharmacokinetics or pharmacodynamics studies conducted in the same species as variability in the physiology among different species may result in differences in drug pharmacokinetics and pharmacodynamics. Unfortunately, dosing regimens are typically extrapolated from closely related avian species or even mammals, which is unideal. Therefore, this critical review aims to collate and evaluate the dosing regimens of selected opioids: tramadol, hydromorphone, buprenorphine, butorphanol, and fentanyl, in avian species and its related safety, efficacy and pharmacokinetic data. Our review found specific dosing regimens not described in the Exotic Animal Formulary for tramadol used in Indian Peafowl (Pavo cristatus), Muscovy Duck (Cairina moschata) and Hispaniolan Parrot (Amazona ventralis); hydromorphone used in Orange-winged Parrot (Amazona amazonica); buprenorphine used in Cockatiel (Nymphicus hollandicus), American Kestrel (Falco sparverius) and Grey Parrot (Psittacus erithacus); and butorphanol used in Hispaniolan Parrot (Amazona ventralis), Broiler Chicken and Indian Peafowl (Pavo cristatus). Cockatiel appeared to not experience analgesic effects for hydromorphone and buprenorphine, and American Kestrel exhibited sex-dependent responses to opioids. The selected opioids were observed to be generally safe, with adverse effects being dose-dependent.

Highlights

There are 10,806 extant species of birds in the world, which are classified to 40 orders, 252 families and 2353 genera [1]. 20.6 million birds were owned as companion in the UnitedStates households and 6% of pet owners in Singapore owned pet birds in 2017 and 2018, respectively [2,3], making birds important for their sentimental value to humans
Articles were searched on PubMed accessed on 30 January 2021 using keywords related to the concept of birds, opioids, and pharmacokinetic (PK) and pharmacodynamic (PD)
The full list of keywords can be found in PK or PD information on the opioid used in particular species of birds

Summary

Introduction

There are 10,806 extant species of birds in the world, which are classified to 40 orders, 252 families and 2353 genera [1]. 20.6 million birds were owned as companion in the UnitedStates households and 6% of pet owners in Singapore owned pet birds in 2017 and 2018, respectively [2,3], making birds important for their sentimental value to humans. In efforts to conserve bird species or keeping them as pets, birds may experience potentially painful injuries, diseases or surgical procedures. Alleviating pain in birds may not be as straightforward as doing so in humans as they are unable to express pain effectively through facial or verbal expressions. There could be situations where birds potentially experience pain, but do not show any behavioral or facial changes. Even when behavioral changes in birds potentially experiencing pain are present, they could still be difficult to assess as this requires the observer to be able to recognize the full range of normal and abnormal behaviors of each species and individual to assess pain. There are other factors to be considered when assessing pain in birds, including age, species, gender, environment, strain, and breed [4,5].

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