Agonist: Chemical substance that binds to and activates receptors on cells within the body, producing a physiological response. Opioid receptor agonists include fentanyl, heroin, oxycodone, morphine and methadone.
Analgesic: Medication formulated to reduce or relieve physical pain (analgesia is the relief of pain). Includes over-the-counter medications as well as prescription opioids.
Antagonist: Chemical substance that binds to and blocks the activation of receptors on cells, preventing a physiological response. The opposite of an agonist. The best-known opioid receptor antagonist is naloxone, a widely available opioid overdose reversal medication.
Buprenorphine: A prescription opioid drug typically used to treat opioid use disorder. When used in this way it is part of a program known as Medication-Assisted Treatment (MAT) or pharmacotherapy. It can be used under the tongue, by injection, as a skin patch or as an implant.
Buvidal: A depot treatment (see the depot treatment entry for more information) containing buprenorphine that is used to treat opioid dependence and addiction. Buvidal is available as a weekly or monthly formulation. It should only ever be administered by a trained and qualified health professional.
Codeine: Pain-relieving opioid medication. Usually used to treat milder pain, coughs and diarrhoea. In many countries, access to codeine has become more tightly regulated in recent years because of concerns about the potential for misuse.
Depot treatment: Specially prepared medication delivered by injection (just under the skin surface or into a muscle) to form a localised mass or ‘depot’. The medicine is released slowly into the body over several days or weeks to be gradually and consistently absorbed by surrounding tissue. This method is sometimes used to administer buprenorphine to treat opioid use disorder, avoiding the need for daily dosing.
Depressant: Substance that inhibits the functioning of the central nervous system. Opioids are one of the main classes of depressant (along with alcohol, sedatives/hypnotics and anti-psychotic medications).
Dual diagnosis: A term used to describe when a person is simultaneously experiencing substance use issues and mental health issues.
Fentanyl: A synthetic opioid which is 50-100 times more potent than morphine. In medical settings, it is usually prescribed to control severe pain (such as in advanced cancer). However, fentanyl is becoming increasingly prominent as an illicitly manufactured and trafficked drug that is often mixed with heroin or other drugs such as cocaine and used in non-pharmaceutical settings.
Half-life: The time it takes for half of the amount of a drug to be removed from the body. Note that this does not only apply to when a drug is first administered. Generally, if half of a drug is removed after one half-life, then the second half-life will remove half of that amount – or a quarter of the original dose.
Heroin: An opioid drug that comes in several different forms, including a fine white powder, coarse granules or small brown “rocks”. Often administered by injection but also commonly smoked.
Illicit drugs: Non-medical substances that are illegal or prohibited by law. Can include heroin and other opioids, cocaine and amphetamine-type stimulants, cannabis and synthetic drugs such as illicitly manufactured fentanyl (IMF) and ecstasy (MDMA).
Medication-assisted treatment: Treatment for opioid use disorder based on the use of medications like methadone, buprenorphine, buprenorphine/naloxone or diamorphine to decrease and/or stabilise a person’s use of opioids. Also known as pharmacotherapy, opioid substitution treatment and abbreviated to MAT.
Methadone: Opioid medication that is used as part of medication assisted treatment for opioid use disorder. Methadone is dispensed only by certified and approved prescribers and is generally required to be obtained in person. It usually comes in the form of a syrup.
Morphine: An opioid analgesic. Morphine is typically given before and after surgery and to treat cancer pain in hospital settings.
Naloxone: An effective opioid overdose reversal medication that displaces opioids from receptors and prevents further receptor activation. Can be lifesaving if administered in time; however, reversal is temporary and patients must still be treated medically. For more information, see our dedicated Naloxone page.
Naltrexone: Long-acting, prescription opioid antagonist medication that is sometimes used to treat opioid use disorder but more often alcohol dependence, partly by suppressing the positive feelings normally associated with consumption of those substances. Most commonly taken as a tablet but can also be administered as an implant.
Opioid: An umbrella term inclusive of natural opiates found in the opium poppy and their synthetic and semi-synthetic forms. Opioids influence opioid receptors on nerve cells in the body and brain, reducing the intensity of pain signals and producing a sense of euphoria. Commonly used to refer to a class of drugs that includes illicit substances such as heroin as well as prescription analgesics.
Opioid Use Disorder: Medical condition in which a person’s use of opioids has become problematic. Diagnosis typically based on the user lacking control over and being unable to reduce usage, experiencing social problems (at school, work and/or home) and feeling compulsive cravings for the substance(s). Preferred by many to terms such as ‘opioid abuse’, ‘opioid dependence’ and ‘opioid addiction.’
Over-the-counter (OTC): Approved method of dispensing medication through pharmacies without a prior prescription. A requirement for ‘OTC’ medicine includes having a discussion with the pharmacist before they can dispense the medicine. Medications sold ‘OTC’ are sometimes not government-subsidised so can be more expensive than if prescribed.
Overdose: Overloading of the body with a drug (either pharmaceutical or illicit) taken in excessive amounts. A type of poisoning or injury that can be fatal or non-fatal. Opioid overdose can suppress the central nervous and respiratory systems and cause breathing to stop.
OxyContin: A common opioid-based medication with oxycodone as its active ingredient. Taken as a tablet to relieve severe chronic pain, including pain caused by cancer. Its wide use has been implicated in the North American opioid epidemic.
Percocet: Opioid pharmaceutical tablet containing oxycodone and acetaminophen used to relieve moderate to severe pain.
Person who uses drugs/people who use drugs: A term of address which is preferred to now-outdated terms such as ‘drug user’ or ‘drug addict’, which are considered derogatory and stigmatising by many people.
Pharmaceutical drugs: Substances developed and manufactured by pharmaceutical companies and dispensed by pharmacists to treat medical conditions.
Pharmacotherapy: Treatment for opioid use disorder that uses medications. See entry for Medication-assisted treatment.
Polydrug use: Taking one drug when under the influence of another drug is known as polydrug use. The use of multiple substances (pharmaceutical, illicit, alcohol, or a combination) can be over a long time because some drugs have an effect for days – see half-life. Harms from polydrug use have been rising.
Receptor: Molecule on the surface of a cell within the human body that recognises and transmits messages from specific chemicals. Th activation and blocking of receptors in the body is what causes the physiological effects of drug use.
Stigma: Negative attitudes and beliefs towards a person or their particular circumstances – in this context, a bias or prejudice that invokes fear and discrimination against someone who uses drugs, their friends or family or the people who work with them such as health care providers.
Sublocade: A depot buprenorphine treatment used to treat opioid dependence and addiction. Sublocade is administered by injection and is available as monthly formulation. The depot gradually releases buprenorphine at a controlled rate all month. It should only ever be administered by a trained and qualified health professional.
Suboxone: A brand-name medication used to treat opioid use disorder that contains naloxone and buprenorphine. Taken as a tablet or film that is administered orally.
Tapering: Gradually reducing the amount of medication regularly used. Carried out under the supervision of a doctor who develops a plan to slowly cut down consumption.
Telemedicine: The practice of delivering clinical services to a patient remotely. The provider and patient do not meet physically for consultations but communicate via phone or video-conferencing programs like Zoom.
Tolerance: A condition in which the human body develops resistance (or a decrease in response) to a drug with the result that higher-than-standard doses are needed to produce the desired effect. The risk of tolerance developing rises with prolonged use.
Tramadol: An opioid medication used to treat pain. Although it is generally considered to be less habit forming than other prescription opioids medications, it carries risks like all drugs. There is increasing evidence of harms related to tramadol in some African and West Asian countries.
Vicodin: The brand-name of a hydrocodone-acetaminophen combination used in tablet form to relieve moderate and severe pain.
Withdrawal: Symptoms that occur when a person who has developed tolerance of a drug significantly reduces or stops taking that substance after a long period. Can include negative emotions such as stress, anxiety and/or depression, and physical effects such as nausea, vomiting, muscle aches, cramping and seizures.