Hi.<br/> Alcohol is one of the most widely used drug substances in the world.<br/>(<a href='http://www.nlm.nih.gov/medlineplus/ency/article/001944.htm' target='_blank' rel='nofollow'>http://www.nlm.nih.gov/medlineplus/ency/article/001944.htm</a>) <br/><br/>What is a drug substance?<br/><br/>Thanks in advance