Have you tried Cosequin?  I am including a few links that you may want to
check.  Please note that this is for long-term treatment.
http://www.whitebearanimalhospital.com/Handouts/Files/FIC.htm

http://www.catdoctor.com/thestore/prods/cdmed102.html

http://www.nutramaxlabs.com/veterinary/cosequincat.htm#vet

http://www.mysa.com/pets/askn.shtml

MaryL
(take out the litter to reply)

This might sound a bit weird, but perhaps "massaging" his "urinary tract"
area help loosen up the crystals so he can pass them?

Tom,

This goes WAY back -- to a cat I adopted in 1965.  I would certainly want
for you to check with your vet before using this, but it worked wonders for
my cat.  He had a continuous series of bladder problems, and at one time had
exploratory surgery after which the vet said the walls of the bladder were
thickened beyond any he had seen.  He was not expected to live, but he
outlasted anything that was predicted -- he lived to be almost 20 years of
age.  We went through a continuous round of treatments as the infection
returned again and again.  Finally, one vet recommended that I give him
250mg of Vitamin C morning and evening to acidify the urine.  He said the
excess would be excreted in the urine.  It was truly remarkable.  He never
had another bladder problem from that time on, and I gave him Vitamin C
twice a day for the rest of his life.  I "shopped around" to find the
smallest tablets I could find because some Vitamin C tablets are very large
and can be very bitter to the taste.

MaryL
(take out the litter to reply)

First, feed only wet food. Second, look for formulas with the lowest Magnesium
in them (http://webpages.charter.net/katkarma/canfood.htm), I'm assuming you
have struvite crystals. You could also try feeding a urine acidifier, look
for stuff with DL-methionine (sp?).

I had a cat that had this problem and had to give her two different pills twice
a day.  It was fairly effective, but things would still flair up sometimes
anyway.

Ask your vet.

Robyn

Feed mainly a good quality CANNED food (Science diet, Wellness, Innova).
Look for low magnesium and don't worry about ash.  Dry food should only
be used for treats.  Friskies dental diet (in moderation) can help the
teeth.  Cats get most of their water from their food and canned food is
70 to 75 percent water.  I very rarely see my cats drink water since
they eat mostly canned food.

                 -MIKE

Thanks everyone, I'm massaging his belly, giving him new antibiotics, canned
prescription food (low magnesium) and starting Vit-c.