anyone have experience giving their cat Milbemax?

I recently moved to Spain, to a heartworm-risk area. My 6 year-old cat
Kotyo is an indoor-only cat, and we do have mosquito screens on all our
windows, but still mosquitoes seem to get in from time to time. So I
need to get some heartworm protection for him.

I've found that the only heartworm-prevention medicine I can get from my
vet here in Spain seems to be Milbemax (made by Novartis).

I've never heard of it before. If anyone has any experience giving it to
their cats, can you tell me about it? Have there been any side-effects,
bad reactions, etc?

My little monster has a sensitive stomach, so he's on Hill's i/d canned
food. He throws up any kind of dry food. I don't want to give him an
upset tummy with the Milbemax. He also has some urinary problems (he got
blocked in March of last year and was at the vet's for a week), and he
still has infrequent episodes where he strains/passes some blood in the
litterbox. Is it safe to give Milbemax to cats which are prone to
blockages/UTIs?

I looked at Novartis' Milbemax info site
(http://www.ah.novartis.com/products/...ilbemax.shtml), but they
mostly seem to have information about giving it to dogs...

thanks,
Nadia and Kotyo

--
Little Monster pictures: http://picasaweb.google.com/nnakova/Kotyo
Blog: http://littlemonstermusings.blogspot.com/