They are classified in terms of medical use, dangerousness, and
abuse potential. DEA Schedule I drugs have "no acceptable medical
use " (which has been debatable, in the case of marijuana, for
instance); Schedule II drugs consist of those opiate-based drugs
which have been determined to have high abuse potential; Schedule
III drugs = intermediate to high abuse potential; Schedule IV drugs
have anywhere from low to high abuse potential, depending upon the
dose of the drug and frequency with which it is taken.