Zabine's Story

Thank you very much for creating, and my condolences to you for PB's tragic circumstances. I hope he pulls through, and send my heartfelt wishes for his recovery.
You see, my precious Zabine (a six-year-old Persian cat) died a year ago after a Metacam injection followed by a single oral dose. Two pathologists guessed that it was a viral infection (probably feline panleukopenia, FPV), but neither performed any tests to support their conclusions -- and ignored the fact that I supplied an unbroken record of FPV vaccination certificates dating back to when Sabine was eight weeks old. Neither pathologist mentioned the role of Metacam in Zabine's death, even through the gastrointestinal damage and low white blood cell count were strikingly similar to those described in the clinical tests filed with EMEA and the FDA a few years ago. I had to threaten the second pathologist with disciplinary action before he would even discuss his report with me; his assistant told me that he had been ordered by the drug company (who paid for the pathology report) not to communicate with me.
[Important note: You won't get much useful information regarding cats by reading the literature about Metacam Oral -- it's only approved for dogs, so no mention is made of cats except "do not use in cats." However, Metacam Solution for Injection is approved for one-time use in cats, and its literature has much more interesting information regarding cats, especially regarding repeated doses.]
I've been researching statements made by my vet and several others, and it's pretty scary how misinformed veterinary "professionals" can be.
See  "Frequently Heard Statements About Metacam" PDF document.
Approval Status. In "P.B.'s story" you write that you were informed that Metacam "was in use in Canada and was awaiting approval here in the states." Well, here in Canada, Metacam Oral is NOT approved for cats (in fact, it's not approved nor pending approval for cats anywhere in the world), although some vets do use it. If you search the FDA website, you will not find any pending applications for Metacam Oral; it is certainly not "awaiting approval" for any species. Ironically, in Canada some vets tell me that "it's been used in Europe for ten years" (perhaps for humans, but certainly not for cats). This bull--it is obviously not confined to the USA.
Warnings for Human Use. Boehringer-Ingelheim also markets meloxicam (the active ingredient in Metacam) for human use, under the trade name Mobic. Another useful piece of information to post is the prescribing information for Mobic, which contains mandatory four-page client information sheet at the end of the document which must be handed to the patient along with the prescription:
These "black box" warnings were issued in August 2005 (and possibly earlier, but I can't be certain); this link is to the most recent (July 2006) version on the MedWatch section of the FDA website.
After reading this document (and considering that cats are much more sensitive to most drugs than humans and dogs), the first question that comes to mind is "so why doesn't the FDA require vets to hand out a similar warning sheet when Metacam is prescribed for cats?" The answer is simple: the FDA has not approved repeated doses of Metacam for cats, and mandating a warning would constitute a tacit form of approval in cats.
The next logical question would be "if there are such serious risks in humans, why don't vets themselves inform their clients of those risks?" That's a tough one to answer accurately; I can only say that my vet insists that Metacam is "safe" (but clearly does not understand the implications of a narrow margin of safety in cats, as described in the Yahoo Answer referenced earlier), and that there's a powerful financial motivation, described next. 
Financial Motivation. My vet invoice (now totaling over C$3,000, which is why I'm going to court over this) shows a charge of C$22.50 (about US$20) for a prescription of four 0.4 mg doses of Metacam (a total of 1.6 mg of the active ingredient meloxicam). Let's do some simple math: US$20 divided by 0.0016 grams = US$12,500 per gram. By comparison, the black-market street price of heroin and cocaine is US$130/gram (adjusted for purity). My vet sells Metacam for one hundred times the black-market price of cocaine.
I hope you can use this information (slightly reformatted to protect my anonymity; no mention of Zabine's real name for the time being, please) in your efforts to educate people regarding the risks of Metacam in cats. My very best wishes to you and PB, and I sincerely hope he makes it through this ordeal.