That's exactly the case. Many drugs are basic amines, and basic amines don't always form the best behaved of solids - some have a tendency to form intractable oils. Usually they crystallize much better if you can find a good salt form. Also, in many cases, the free amine is not water soluble while the salt form is - this can make a difference in how the drug is administered.
There are lists of "pharmaceutically acceptable salt forms" which are essentially acids that can be added to basic drugs to improve properties, but would not cause additional pharmaceutical effects in the body. Hydrochlorides, sulfates, tartrates, maleates, and dozens of other salt forms have been used.