Boo did have Milbemax the first time, but as we use Drontal for Coz we gave him Drontal this time. As I said earlier, I don't think it was the drontal that made him sick, but I will be sure to keep an eye on him next time and if it happens again ....Milbemax it is. Only problem it's a bit more tricky to buy over the internet as you need a prescription.