Comparative and Veterinary Pharmacology

The most common routes of administration of opioids are by injection, intra-
muscular, subcutaneous or intravenous. In addition, oral formulations of morphine
are used in dogs (Dohoo et al. 1994 ). The epidural route has also been reported in
several species (Tung and Yaksh 1982 ) and the use of fentanyl transdermal patches
has been reported for use in dogs, cats, horses and pigs (Kyles et al. 1996 ). See
Tables 2 – 4 for opioid doses and intervals in small animals (Table 2 ), companion
animals, birds and reptiles (Table 3 ) and farm animals (Table 4 ).
The specific opioid-reversing agents, such as naloxone, also exert the same
effects in animals and they can be used to terminate the effects of opioids as in
humans. In fact, a specific agent, diprenorphine, was developed to reverse etorphine
(a potent opioid used for immobilisation in animals).

Table 3Doses and intervals for opioids in companion animals, birds and

reptiles

Drug Dog Cat Bird Reptiles

Buprenorphine

6–12 h

0.005–0.02 0.005–0.02 0.01–0.05 0.4–1

Butorphanol

2–4 h

0.2–0.6 0.2–0.8 1–4 1

Fentanyl

0.5 h (i/v)

0.001–0.005 – 0.02–0.2 –

Meperidine

(Pethidine)

2–3 h

3–10 3–10 – 1–4

Morphine

4–8 h

0.1–1 0.1–0.2 200 0.05–4

Nalbuphine

3–4 h

0.3–0.5 0.3–0.5 – –

Oxymorphone

2–4 h

0.05–0.2 0.05–0.4 – –

All doses in mg/kg for subcutaneous or intramuscular injections. Data from

Dobromylskyj et al. ( 2000 ); Machin ( 2005 ); Mosley ( 2005 )

Table 2Doses and intervals for opioids in small animals

Drug Mouse Rat Guinea-pig Rabbit

Buprenorphine

6–12 h

0.05–0.1 0.01–0.05 0.05 0.01–0.05

Butorphanol

4h

1–2 1–2 – 0.1–05

Meperidine

(Pethidine)

2–4 h

10–20 10–20 10–20 5–10

Morphine

4h

2–5 2–5 2–5 2–5

Nalbuphine

4h

2–4 1–2 1–2 1–2

All doses are in mg/kg for subcutaneous or intramuscular injection. Data from

Flecknell ( 1996 ); Cowan et al. ( 1997 ); Dobromylskyj et al. ( 2000 )

Pain and Analgesia in Domestic Animals 177