I have problems with maize starch that is used as a filler with a lot of pills, so always have to check the labels. The liquid options are sometimes the easiest for me. If you have a choice, there are a variety of things that get used as fillers - you want to avoid maize starch, and probably microcrystalline cellulose (a highly processed form of starch), but lactose is fairly common as a filler, and if you want an inert filler, then talc could also be used.
Just be aware though that sometimes the fillers are chosen for particular properties, and you need them to help get the drug absorbed in the right way in your body. If you did just take the pure drug, my guess is that most of it would end up hitting your mouth and throat hard and not necessarily getting absorbed in the best way.
