No no no, please do not mention anything about drugs, you will get a lifetime ban.
Under Sec. 212 (8 U.S.C.1182) you are ineligible to receive visas and ineligible to be admitted to the United States if you 'voluntarily admit to having committed a crime involving moral turpitude
Here's a recent story: http://www.vancouversun.com/news/White+Rock+woman+barred+fro...