Methadone v Buprenorphine in cats

RE: Methadone v Buprenorphine in cats

Evelyn Barbour-Hill — Fri, 28 Feb 2020 00:13:01 GMT

[quote userid="12930" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/28924/methadone-v-buprenorphine-in-cats/219892"] I would be uncomfortable leaving a barely-responsive cat in a kennel not being monitored[/quote]

Ah. Shouldn't the dedicated recovery-room RVN be doing that?

RE: Methadone v Buprenorphine in cats

Beats — Thu, 27 Feb 2020 23:01:29 GMT

Great discussion! I'm reading with interest :-)

Specifically relating to cat spays, I can only speak my own limited experience and thoughts.

I tend to inject a cat with medetomidine (high-ish doses) and an opioid, then about 2 minutes later with ketamine iv, I then microchip (assuming being done), squirt larynx with lidocaine, clip side, intubate (3mm ET tube in 5month kitten at 2kg), put in theatre on O2 and sometimes some iso, clean, spay, inject atipamezole and put in kennel. I give metacam at some point SC and am not fussy regarding the timing of this.

I don't consider myself an outstanding cat spay-er, but they are up and around again without any demonstrable signs of pain very quickly afterwards. I think that avoidance of pain with good surgery is probably the thing that makes the biggest difference, but that is a learned skill with no short-cuts but practice.

So my thoughts on choice of opioid:

1) The most likely time to see pain is on initial injection - I do IM (I appreciate there is a strong argument for SC, I do IM largely for efficiency). This impacts my choice of opioid - buprenorphine is a larger volume to inject than either butorphanol or methadone. Buprenorphine in multi-use vials stings making it a particularly poor choice in my opinion when single-use vials are not stocked.

2) Buprenorphine has a reputation (perhaps incorrectly?) of taking 20-40mins to reach analgesic effect - with the way i currently work my cat spays, the cat will be spayed before it is doing anything. If given SC, it's effect is reported by at least one paper to be inferior to transmucosal IIRC, i.e. if giving SC buprenorphine really mightn't be great choice of analgesic?

3) Buprenorphine has a reputation for lasting longer than methadone, this may or may not be accurate, however could be a benefit. This is offset against not being present at time of most likely pain stimulation (point 2 above).

4) Buprenorphine has a reputation (presumably rightly so) for being better analgesic than butorphanol, again with respect to point (2), it is worth noting that butorphanol however works faster and is likely to be having its weak analgesic effect during the actual surgery, while buprenorphine may not be having an effect at this time.

5) Methadone and butorphanol are both notably sedative and contribute to the anesthesia to a degree that buprenorphine is not.

6) I have never used methadone in a cat spay [I tend to use butorphanol or buprenorphine], but can see the logic and can see no obvious reason that this is not the preferred option [my only reasons for not doing so being]:

a) inexperience

b) having to account for and record the use in a controlled drugs book [this is probably the crucial reason]

c) being satisfied with my current approach

Regarding midazolam, I associate its use in young cats with worse recoveries from anesthesia. Regarding the quad protocol, I haven't tried it SC, but IM it is a large volume and stings with the ketamine [undoubedly the most demonstrably aversive part of spaying a cat if done], it also flattens the cats much deeper from an IM injection than I am comfortable, to the extent that they never need any isoflurane for a spay procedure in my limited experience - not used to them being quite so deep, I find this disconcerting personally.

Regarding not reversing the medetomidine, I'd rather see the cat fully recovered and maintaining it's own body temperature in a kennel on its own than lying comatose for a prolonged period. They recover well in my experience and I have not noted a problem with post-op pain. I would be uncomfortable leaving a barely-responsive cat in a kennel not being monitored, and would prefer my assistant to lend a hand monitoring the next cat spay than still watching the last one.

RE: Methadone v Buprenorphine in cats

Sarah Keir — Thu, 27 Feb 2020 21:02:36 GMT

I am glad you had time to the papers - I had 5 minutes between appointments. Thank you for the summary!

RE: Methadone v Buprenorphine in cats

Michael Woodhouse — Thu, 27 Feb 2020 20:56:27 GMT

Sarah Keirthe studies are crap and IMO don't reflect my practice (and I suspect a lot of other people). NSAID only given at the end of the study (you'd think authors researching analgesia would understand the concept of wind-up). Medetomidine reversed. I've not used the quad protocol (use the licenced triple without the addition of midazolam) but the great majority need no additional iso - does the quad even provide full anaesthesia?

It seems wrong doing a study when you withhold a NSAID and reverse another analgesic!!!

Open to change with good evidence, I'm seeing none presented here.

RE: Methadone v Buprenorphine in cats

Iain Richards — Thu, 27 Feb 2020 18:14:47 GMT

I take the point of challenging and re-visiting existing protocols, but I also wonder if there is a culture that nothing must ever be in pain. Pain is subjective and, unless constant and severe, not in itself a problem. As long as the cat (in this case) is moving, interacting, eating and behaving in a relatively normal manner, is further pain relief needed?

RE: Methadone v Buprenorphine in cats

Sarah Keir — Thu, 27 Feb 2020 18:13:17 GMT

Comparison between methadone and buprenorphine within the QUAD protocol for perioperative analgesia in cats undergoing ovariohysterectomy https://journals.sagepub.com/doi/10.1177/1098612X18798840

Comparison between methadone and buprenorphine within the QUAD protocol for perioperative analgesia in cats undergoing ovariohysterectomy https://research-information.bris.ac.uk/files/177116160/Main_documentnothighlightedv2.pdf

Buprenorphine versus butorphanol in cat spays https://bestbetsforvets.org/bet/488

https://onlinelibrary.wiley.com/doi/pdf/10.1111/jvim.12346

RE: Methadone v Buprenorphine in cats

Kate Richardson — Thu, 27 Feb 2020 17:32:38 GMT

[quote userid="19697" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/28924/methadone-v-buprenorphine-in-cats/219882"]My concern would be that cats are very good at hiding pain / we are poor at detecting it, especially whilst the patient is still sedated from the effect of other agents administered concurrently. Most practices are not routinely using validated pain scoring methods to monitor feline patients post operatively and could potentially be missing cats that are in pain. Once the patient is discharged it is likely that the owner would be even worse at detecting whether their cat is in pain.[/quote]

100% appreciate that. I guess my question is how significant a difference does methadone make compared to buprenorphine (if it truly does) and how much does surgical technique impact on these studies.

[quote userid="19697" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/28924/methadone-v-buprenorphine-in-cats/219882"]Studies like this provide evidence that challenges previous practice and suggests that it could be time to review current protocols and see if there are simple analgesic improvements that could be made. [/quote]

Am always reviewing my protocols, this is one where I struggle to see a clinical benefit to our current protocol of using buprenoprphine. We do use medetomidine in our premeds for most cats and I 100% agree re its analgesic effects, so much that sometimes during a prolonged dental procedure (of which I do a lot) we give an additional dose as there is a sudden change in anaesthetic depth with nothing else having changed, and I think it is due the medetomidine wearing off, and they settle right back down following a small dose iv. I do get queries from other vets within the group asking why we don't use methadone because its proven to be better, but I don't think it is as black and white as that- the individual surgeon needs to be taken into account as well- some induce more pain than others, (and not always related to years qualified- one of the best surgeons we had here was 2 years qualified) and the enviromnment and external stimulation plays a role too.

RE: Methadone v Buprenorphine in cats

Lizzie Barker — Thu, 27 Feb 2020 17:06:06 GMT

The analgesic effect of medetomidine would be dose dependent and any analgesic effect of butorphanol would be of very short duration.

My concern would be that cats are very good at hiding pain / we are poor at detecting it, especially whilst the patient is still sedated from the effect of other agents administered concurrently. Most practices are not routinely using validated pain scoring methods to monitor feline patients post operatively and could potentially be missing cats that are in pain. Once the patient is discharged it is likely that the owner would be even worse at detecting whether their cat is in pain.

Studies like this provide evidence that challenges previous practice and suggests that it could be time to review current protocols and see if there are simple analgesic improvements that could be made.

RE: Methadone v Buprenorphine in cats

Evelyn Barbour-Hill — Thu, 27 Feb 2020 16:54:32 GMT

[quote userid="3169" url="~/001/veterinary-clinical/small-animal/anaesthesia/f/discussions/28924/methadone-v-buprenorphine-in-cats/219880"]Can't remember ever having to give a cat additional analgesia. Try not to reverse the medetomidine as that adds significantly to analgesia IMO. [/quote]

Agree!!!

RE: Methadone v Buprenorphine in cats

Michael Woodhouse — Thu, 27 Feb 2020 16:40:02 GMT

Yes, very happy with triple combination using butorphanol. NSAID at same time. Can't remember ever having to give a cat additional analgesia. Try not to reverse the medetomidine as that adds significantly to analgesia IMO.

RE: Methadone v Buprenorphine in cats

Iain Richards — Thu, 27 Feb 2020 16:10:00 GMT

Pure observation - based on passing the cages of recovering animals. I see no difference in meth/dom, i/v induction, iso to dom/butorph/ket, to dom/buprenorph/ket. They all seem happy cats.