Final answer:
Drug therapy for substance dependence can lead to drug substitution or cross-dependence.
Step-by-step explanation:
Drug therapy for substance dependence can be of limited use due to several reasons. One potentially serious risk of such therapy is that it could substitute one abused drug for another. This is known as drug substitution or cross-dependence. For example, using methadone to treat heroin addiction can lead to dependence on methadone.
Learn more about Drug therapy and substance dependence