Plus-Hex CLINICAL
Opioids
Buprenorphine
For moderate to severe pain , full µ agonists , such as methadone ( Figure 2 ) or hydromorphone , are recommended .
For mild to moderate pain , buprenorphine at 0.01 – 0.05 mg / kg can be administered via the subcutaneous ( SC ), intramuscular ( IM ), intravenous ( IV ) or oral transmucosal ( OTM ) route , every 6 – 8 hours .
A study by Katzenbach et al . [ 1 ] suggested a different interval for the frequency of buprenorphine administration in ferrets . Maximum plasma concentrations were achieved 9 min post IM injection of 0.04 mg / kg , and the half-life was 3.65 hours [ 1 ] . Therefore , it may be useful to dose buprenorphine every 4 – 6 hours . van Zeeland and Schoemaker [ 2 ] reported ‘ profound sedation ’ with doses of buprenorphine above 0.02 mg / kg .
In laboratory ferrets , a long-acting ( 72-hour duration ) formulation of buprenorphine ( Bup-XR ) at 0.6 mg / kg SC has been shown to significantly lessen the reaction to surgical-site palpation ( as well as being associated with lower ‘ posture scores ’ and respiratory rates ) compared with buprenorphine hydrochloride in the first 24 hours after ovariohysterectomy [ 3 ] .
In cats , IV buprenorphine is superior to other routes of administration , with the order of preference of different routes appearing to be IV > IM > SC > OTM [ 4 , 5 ] . To the authors ' knowledge , there are no studies on OTM administration of buprenorphine in ferrets , but there is information to suggest that the pH of ferret saliva is similar to that of cats , so OTM buprenorphine is suggested at doses of 0.04 – 0.06 mg / kg every 6 – 8 hours [ 6 ] .
Ferrets can be aversive to oral medications , so ensuring positive reinforcement and giving a high-reward treat may help ( Figure 1 ).
Figure 2 . A ferret receiving intramuscular premedication of methadone , midazolam and medetomidine before surgery .
Methadone
To the authors ' knowledge , methadone is often administered to ferrets at doses used in cats . Kapaldo and Eshar [ 7 ] advise administering methadone at 0.2 – 0.5 mg / kg every 2 – 3 hours , whereas Johnson- Delaney and Lennox [ 8 ] advise using a dose of 0.2 mg / kg .
Shin et al . [ 9 ] describe a study in which 0.3 mg / kg methadone was administered to ferrets either SC or IV . They found that the elimination half-life was 2 hours when both routes were modelled simultaneously . The minimum effective concentration ( MEC ) of methadone in ferrets is unknown . In dogs , the MEC of methadone and thermal antinociception is reported as being 17.1 ng / ml ( when administered at 0.2 mg / kg IV followed by a 0.1 mg / kg / hour constant rate infusion ( CRI )), and in cats it has been reported as 39.2 – 124 ng / ml ( at 0.6 mg / kg IM ). In humans it is 59.2 ng / ml . In both the SC and IV groups , the MEC for methadone stayed above the level reported to provide thermal antinociception in dogs ( 17.1 ng / ml ) but for only 45 min post injection . The level of antinociception was not tested .
Surprisingly , bioavailability was higher in the SC group , which may be due to slower absorption than elimination . In the SC group , the MEC increased above the human MEC for methadone , but only for 5 min post injection .
Figure 1 . A ferret with a right eye ulcer taking Hill ' s a / d from a spoon , following oral medication .
The reported side effects included whole-body shaking , digging , increased locomotion ( in the IV group , taken to be a sign of dysphoria ) or sedation ( in both groups ). However , it is important to note that the ferrets were pain-free before being injected , which may account for the noticeable side effects . Lip licking was also noticed in both groups . The paper concludes that further research is required in order to make accurate dosing recommendations .
Volume 40 ( 1 ) • February 2025
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