Addiction: Compulsive use of a substance that occurs when it is used in a way other than intended. Patients have cravings when the substance is withdrawn, with an overriding inability to control their perceived need for the substance, even though there may be an awareness that the substance, or overuse of the substance, is harmful.

Dependence: A state in which the person feels that they can only function normally when using a specific substance. Abrupt withdrawal of the substance causes withdrawal symptoms.

Pseudoaddiction: The mistaken assumption that a patient who is seeking pain relief is addicted to a substance.

Tolerance: Occurs when the patient no longer has a therapeutic response to the drug and a higher dose is required to achieve the prior effectiveness.