The preferred drug for treating ADHD in a 7 yr old boy, whose father has a history of substance abuse :
Methylphenidate
Atomoxetine
Clonidine
Dexamphetamine
Methylphenidate is a stimulant used as DOC for ADHD, but stimulants are contraindicated in patient with family history of substance abuse. Therefore non stimulants are used and Atomoxetine is preferred over Clonidine.