Drug: any chemical that alters your mind or body. http://dictionary.reference.com/browse/Drug?s=t a chemical substance used in the treatment, cure, prevention, or diagnosis of disease or used to otherwise enhance physical or mental well-being.
Withdrawal effects: negative symptoms that happen when the drug wears off. http://www.medterms.com/script/main/art.asp?articlekey=9974 Abnormal physical or psychological features that follow the abrupt discontinuation of a drug that has the capability of producing physical dependence.