In addition, it tends to cause less vomiting and regurgitation than other pure-opiate (codeine, morphine) and synthetic pure-opioid agonists (oxycodone, hydromorphone) when given as a continuous post-operative infusion. As with other pure-opioid agonists, fentanyl can be associated with dysphoria in both dogs and cats.Transdermal fentanyl has also been used for many years in dogs and cats for post-operative analgesia. This is usually done with off-label fentanyl patches manufactured for humans with chronic pain. In 2012, a highly concentrated (50 mg/mL) transdermal solution, trade name Recuvyra, has become commercially available for dogs only. It is FDA approved to provide four days of analgesia after a single application before surgery. It is not approved for multiple doses or other species. The drug is also approved in Europe. See also
List of fentanyl analogues
Purdue Pharma

References
Further reading
External links

Fentanyl. U.S. National Library of Medicine (Report). Drug Information Portal. National Institutes of Health. Fentanyl. US DEA information (Report). Archived from the original on 19 October 2002. Fentanyl. National Institute for Occupational Safety and Health (Report). Emergency Response Database. Center for Disease Control. 8 July 2021. "Fentanyl landscape | PiHKAL · info". isomerdesign.com.
Zygodactyl tracks have been found dating to 120–110 million years ago (early Cretaceous), 50 million years before the first identified zygodactyl fossils. All Psittaciformes, Cuculiformes, the majority of Piciformes and the osprey are zygodactyl. Heterodactyly
Heterodactyly is like zygodactyly, except that digits 3 and 4 point forward and digits 1 and 2 point back. This is found only in trogons, though the enantiornithean Dalingheornis might also have had this arrangement. Pamprodactyly
Pamprodactyly is an arrangement in which all four toes point forward, outer toes (toe 1 and sometimes 4) often if not regularly reversible. It is a characteristic of swifts (Apodidae) and mousebirds (Coliiformes). Chameleons
The feet of chameleons are organized into bundles of a group of two and a group of three digits which oppose one another to grasp branches in a pincer-like arrangement. This condition has been called zygodactyly or didactyly, but the specific arrangement in chameleons does not fit either definition. The feet of the front limbs in chameleons, for instance, are organized into a medial bundle of digits 1, 2 and 3, and a lateral bundle of digits 4 and 5, while the feet of the hind limbs are organized into a medial bundle of digits 1 and 2, and a lateral bundle of digits 3, 4 and 5. On the other hand, zygodactyly involves digits 1 and 4 opposing digits 2 and 3, which is an arrangement that chameleons do not exhibit in either front or hind limbs.