Use of a prescribed drug in a manner other than directed. The term can mean overuse, underuse, improper dose sequencing, or lending or borrowing another person's medication, with or without harmful consequences.
apply to a wrong thing or person; apply badly or incorrectly; "The words are misapplied in this context"; "You are misapplying the name of this religious group"
change the inherent purpose or function of something; "Don't abuse the system"; "The director of the factory misused the funds intended for the health care of his workers"