| Addiction: | a pattern of compulsive drug use, characterized by continued craving for an opioid and the need to use the drug for an effect other than pain relief. |
| Agonist: | a drug that binds to pain receptors to produce analgesia. |
| Analgesia: | absence of pain in response to a stimulus that would normally cause pain. |
| Analgesic ceiling: | a dose beyond which a further increase in dose does not produce more analgesia. |
| Breakthrough pain: | pain that occurs before the next scheduled dose of an analgesic. |
| Coanalgesic: | a drug that has a primary purpose other than pain relief, such as an antidepressant or anti-convulsant, that can also augment analgesia for some painful conditions. May also be referred to as an adjuvant analgesic. |
| Dependence: | universal physiological and pharmacological phenomenon that occurs following the regular use of opioids for more than two weeks. |
| Modulation: | the activities of descending neurological pathways from the brain that inhibit the cells responsible for transmitting pain signals. |
| Mu agonist: | a type of opioid drug; mu agonists include morphine and other opioid drugs that produce analgesia by binding to mu receptor sites in the nervous system. |
| Narcotic: | a term previously used to refer to opioid drugs. The term "narcotic" is currently used to refer to a wide variety of substances of potential abuse. |
| Neuropathic pain: | abnormal processing of sensory input by the peripheral or central nervous system. |
| Nociceptive pain: | occurs when the brain perceives impulses arising from specialized nerve endings (nociceptors), signaling noxious exposure or traumatic injury; it may be somatic pain caused by injury to bone, joint, skin, or connective tissues; or visceral pain, caused by painful stimulation of visceral organs, such as the gastrointestinal tract. [L. nocere to injure] |
| Nonopioid: | refers to acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDs). |
| Noxious stimulus: | a stimulus that damages normal tissue. |
| Opioid: | all naturally occurring and synthetic drugs with morphine-like activity. |
| Opioid dose sparing effect: | the dose of opioid may be lowered when a nonopioid is used. |
| Opioid naive patients: | individuals who have not previously received opioid drugs and now, due often to trauma or surgery, receive regular doses of opioids. |
| Pain perception: | the process of recognizing and responding to pain. |
| Physical dependence: | a phenomenon that occurs with patients who have been taking long-term opioids; abrupt discontinuation of the drug, or the administration of an antagonist drug, causes physical withdrawal symptoms. |
| Titrating to effect: | the practice of continuing to increase the dose of an opioid until the patient obtains a desired level of pain relief or until adverse reactions are unmanageable and intolerable. |
| Tolerance: | refers to the requirement for a larger dose of opioid analgesia to maintain the original analgesic effect. |
| Transduction: | conversion of one form of energy to another. |
| Transmission: | movement of pain impulses from the site of transduction to the brain. |