While you're likely to find that your prescription drugs cost less than in the US, some over the counter medications may cost more. Recently a friend needed allergy medicine in Italy and paid about $1 per pill for the equivalent of sudafed. Another friend paid about $1 per pill for ibuprofen. So you might want to bring these with you, too, if you use them. Other medications, like aspirin, will be about the same cost as in the US.
By the way, you'll have to go to the farmacia for these medications, too. All medicines are sold only in pharmacies, although that may change soon. If you're feeling a little ill, the pharmacist may be able to give you advice, too. There are English-speaking pharmacists in most major Italian cities.
Find out more about the Italian pharmacy in the Pharmacy in Italy.