There is no set rule here, don't panic. You're vet is doing fine. Any discussion of liver damage is with weeks of use and if liver damage is already present. Was he tested for liver damage? In any case, don't stop the drug.
Neither of my two vets are too concerned about liver issues, they both say that's more of a concern in dogs and other pets, they don't test before prescribing it. Randy may not agree with this but even if he's right and my vets are wrong (and he may well be, I'm not disputing his conclusions), it is not an immediate life-or-death thing. Its a very slow progression.
Gastric ulcers and a reduced plasma flow to the kidneys are more common in my experience (and according to my vets) but alleviated by providing food with the meds and making sure the rabbit is very well hydrated.
Metacam is also routinely prescribed long-term to rabbits with arthritis so I'm sure there is a lot of anecdotal evidence on long term use, and I haven't seen any dire warnings anywhere. It's still worth looking into -- like a lot of drugs, it hasn't been commonly prescribed for rabbits until the past few years, so more info should be emerging.
Metacam dosages for rabbits are also still a work in progress, my two main vets don't agree on dosages or frequency, neither do the text books. One recommends 0.1 to 0.2 mg/kg every 24 hours, but I've had prescriptions calling for as high as 0.3mg/kg. And I just saw a study on a group of NZ Whites lab rabbits that said a dose of .3 per kg appeared to be too low. I also find different breeds seem to metabolize drugs at different rates, so I'm not even sure strictly going by weight is best. And some forms of pain are worse than others. You just have to experiment -- within limits of course.
But I think the dosage your vet prescribed is well within the limits. I give Pipp, who weighs 1.3 kg or 2.8 lbs, most often a kick-off dose of .4 with .2 after that when she shows signs of pain, usually by 16 hours. I'll go as low as .18 and as high as .25. My 15 lb / 6.8 kg guy was good with just one .8 dose after his neuter.
I was told by a vet tech that the main dose could be split in half for two 12 hour doses, and I've seen that disputed, but I know it certainly doesn't last 24 hours with my rabbits. I checked into some studies that concluded it has a half life of eight hours in rabbits and its completely out of the system at 24 hours, so I'm personally happy with dosing a half dose every 12 hours or a full dose every 16 hours.
I'm just dosing based on the reaction of the individual rabbit and the situation. I stay within the ranges given by both vets, but if the bunny gets 'loopy', they're cut back. If they seem to still be in pain, I go for the higher end. I'm currently giving a full dose to my broken leg guy every (he probably weighs 2.5 lbs as well) every 16 hours until his surgery next week.
I'll be asking the vet about other pain relief options at that time.
ETA: I wrote this before seeing Randy and TH's posts, so we're all in agreement for the immediate future!
PS: My rabbits LOVE the Metacam suspension I get, it tastes like banana or something, they'll happily lap it from the syringe.
sas :clover:
