I've never heard of them being thrown up ... but I suppose if they are bad enough that can happen. Poor baby!!! The Drontal is usually just for tape worms (caused by fleas) ... tape worms are small, flat and white ... they look like pieces of Rice!!! Any other type of worm, needs to be treated with Strongid... a liquid dewormer!!! It is yellow and supposedly banana flavored? hehe
It is relatively inexpensive and you can get it from your vet!

The dewormer works within 24 hours, you should see them being passed (dead) in the feces!

It wouldn't hurt to deworm your other cats, if they haven't been in several months or a year.