could be the food your feeding. It could be a reaction to the meds, it could be a number of things. Have you let the vet know?
What kind of vomit is it? is it whole chunks of food that look like they weren't chewed, is it bile? is it hairballs? is it digested food that was eaten long before your cat vomited?
What kind of vomit is it? is it whole chunks of food that look like they weren't chewed, is it bile? is it hairballs? is it digested food that was eaten long before your cat vomited?