Can orbax cause weight loss??

Zorro's been on Orbax for a little over a month now. He's on half a pill twice a day. He's been a little pudgy for a few months now, and I've been wanting to get his weight down from 3.9kg to 3.6kg. In the last week or so, he hasn't been eating as much as usual. He gets a tiny bit of wet food in the morning and evening, and I leave his dry food out all the time. I usually give him 1/4cup once a day, but its been days since I've had to fill up his dish. I don't think he's getting enough wet food to keep him going though. He's gone from 3.9kg to 3.6 in a week and a half.He's just been to the vet last week for ex-rays and everything, and they said he's ok.
I can't call the vet today since they're closed, but I was just wondering if orbax has been known to cause weight loss. He's on 2.5 mg prednisone every day as well.

I know Orbax, long-term, can cause kidney failure. Sometimes it causes a decreased appetite as well. If I am remembering right.

The Orbax seemed to upset Chase's tummy a little, which made him not eat as much as I would have liked. It got a bit better adding Bene-Bac in, but he didn't eat normally until he was off it.. But he did immensely better on it than he does on Amoxi, so we dealt with it. He didn't lose any weight though.

We've tried Clavamox and Amox before, but the only thing that seems to work is Orbax, and even that doesn't work all that great on his mysterious infection. The vet is baffled so he wants to try the antibiotics for another two months, which will have him on the antibiotics for three months, which I don't like, but I don't really have a choice.

The vet here says to look at it two ways for a chronic infection:
1) you can euthanize the cat
2) you can try the Orbax & if it works it does, even with the possible consequences

I definatly don't want to euthanize him. I'm giving the orbax a try, and if that doesn't work, I'm shipping him off to a teaching hospital for them to look at him.