I have a "no metacam" note in my cats' vet files, and here's why: When I'm thinking about taking a risk, I ask myself:
1) what do I know and don't know about the cause & effect of my proposed action?
2) what is the likelihood that the bad effect(s) will happen?
3) what are the consequences of those bad effects?
If the consquences are bad-severe-permanent (eg., incurable, degenerative disease leading to death), and the probability is "likely - probably-high", then I'm not going to gamble. If the consequences are bad-severe, but probability is "highly unlikely-extremely low" then I *might* take the risk, depending on the circumstances.
Metacam? Here are some considerations (as I understand them):
1) like other NSAIDs, metacam is nephro-toxic; it can reduce bloodflow to kidneys, and tissue damage results; damaged tissues don't function as well; high doses probably cause more severe and extensive damage than low doses, but *some* damage is likely;
2) unlike bladder tissue, kidney tissue doesn't regenerate itself; once tissues are damaged or scarred, their loss of function is thought to be permanent; eg., if 10% of the kidney tissue loses 50% of its function, that tenth of the kidney will probably never do more than about half of its work;
3) as cats age, their renal function declines; one estimate is that about 10% of cats over 10 yrs old will develop CRF;
4) kidney disease isn't usually detectable by standard labwork until around 65-70% of kidney function is already lost; so, a cat's bloodwork may be within "normal" range but it doesn't necessarily mean the kidneys are "just fine"; the kidneys might be functioning at 70% or 60% or 50% capacity and you may not know it.
So if the kidneys take a hit each time metacam is used, and each insult is cumulative (additive), and I don't know how much kidney function (or loss) the cat already has, then for me, personally, the risk and uncertainty are just too great, especially if alternatives are available. Exceptions (IMHO) would be a cat in pain w/ no alternatives, who is facing euthanasia w/o metacam.
Buprenex (buprenorphine) is considered safer for cats, but I don't know how effective it is for arthritis pain and/or longterm use. You might consider asking your vet about Gabapentin (neurontin), in conjunction with one of the glucosamine/chondroitin supplements others have mentioned. A listmember on the Yahoo CRF group has used Gabapentin for her cat's arthritis for over a year (he is 21 yrs old, hypertension, hyperT, CRF dx 2008); has worked wonders for him, with no apparent side effects or interactions w/ his other meds. Her vet compounds a mixture with VAL syrup, so that she gives a 0.2 ml oral dose once a day.
The Veterinary Anesthesia & Analgesia Support Group (VASG.org) site has an overview on longterm use of meds for chronic pain in cats. Its not very specific about different kinds of pain, but does have some info on side effects and cautions.
http://www.vasg.org/newer_options_for_c ... ment_2.htm
http://www.vasg.org/chronic_pain_management.htm
-- some notes from the VASG overview on gabapentin --
Use alone or adjunct (w/ other meds);
Possible side effects - weight gain, transient sedation;
Particularly effective for neuropathic pain and cancer related pain;
Dosed at 2 to 5 mg/kg BID PO;
Metabolized by liver; primarily excreted unchanged by kidneys;
Short half life; fast clearance, requires frequent dosing;
Cautions: dose reduction for impaired renal function (no cautions listed for liver).
I read somewhere that Gabapentin is being studied on a Winn Feline Foundation grant at UC/Davis to determine accurate dosages and adverse effects in cats.
More info on pain meds: AAHA/AAFP Pain Management Guidelines for Dogs and Cats (2007):
http://tiny.cc/PainMgmtGL
(although I was disappointed at the lack of cautions re: metacam... but then Merial was a sponsor for this publication)
This CRF site discusses issues re: metacam and kidneys:
http://www.felinecrf.org/causes_of_crf.htm#metacam
A couple of discussions re: metacam on FDMB:
viewtopic.php?f=3&t=1557#p13128
http://www.felinediabetes.com/phorum5/r ... ?8,1867651
Hope this is helpful -
Deb, angel Evie, and the boys