Medication isn't really based on age but it is based on weight, majority of children at two fall into a "norm" weight catergory.
My kids are bigger and I know others who are as well but they always needed more than other kids when it came to meds...
I give my kids Flintstones, even though they have a good diet it doesnt hurt to be healthy, your body only absorbs so much vitamins and then the rest well we know what happens after...