Addiction Treatment Glossary: Key Terms Explained
The world of addiction treatment is full of acronyms and clinical terms that can make an already stressful process more confusing. This glossary defines the terms you are most likely to encounter, in plain language, so you can ask informed questions and understand your options.
ASAM Criteria
A national standard from the American Society of Addiction Medicine used to match each person to the right intensity of treatment, from outpatient to residential to hospital-based care.
Agonist, partial agonist, and antagonist
Terms describing how a medication acts on opioid receptors. A full agonist (e.g., methadone) activates them; a partial agonist (e.g., buprenorphine) activates them less and has a safety 'ceiling'; an antagonist (e.g., naltrexone) blocks them.
Buprenorphine
A partial-agonist medication for opioid use disorder that reduces cravings and withdrawal with a lower overdose risk; can be prescribed in office-based settings.
Co-occurring disorder / dual diagnosis
When a person has both a substance use disorder and a mental health condition (such as depression, anxiety, or PTSD). Best treated together through integrated care.
Contingency management (CM)
A behavioral treatment that gives tangible rewards for verified healthy behaviors, such as drug-free test results. Strong evidence, especially for stimulant use disorder.
Detox / withdrawal management
Medically supervised care to get through withdrawal safely. It is the first step of treatment, not treatment by itself — ongoing care afterward is what supports lasting recovery.
Fentanyl
A powerful synthetic opioid that now contaminates much of the drug supply, including non-opioid drugs. A major driver of overdose deaths.
Harm reduction
Practical strategies (such as naloxone and not using alone) that reduce the harms of drug use and keep people alive and connected to care.
IOP (Intensive Outpatient Program)
Several hours of treatment a few days per week while living at home — more intensive than standard outpatient, designed to fit around work or family.
MAT / MOUD
Medication-Assisted Treatment / Medication for Opioid Use Disorder — using FDA-approved medications (methadone, buprenorphine, naltrexone) alongside counseling and support.
Methadone
A long-acting full-agonist medication for opioid use disorder, dispensed through licensed opioid treatment programs, that prevents withdrawal and reduces cravings.
Naloxone (Narcan)
A medication that rapidly reverses an opioid overdose. Safe, easy to use, and increasingly available without a prescription.
Naltrexone
An antagonist medication that blocks opioid effects; the extended-release form is given monthly. A person must be fully withdrawn from opioids before starting it.
NAS (Neonatal Abstinence Syndrome)
Temporary, treatable withdrawal in a newborn exposed to opioids during pregnancy. Hospitals manage it routinely.
PHP (Partial Hospitalization Program)
A full daytime schedule of treatment while living at home or in supportive housing — more intensive than IOP, less than residential.
Relapse
A return to substance use after a period of abstinence. Treated as a signal to adjust the recovery plan, not as failure.
Tolerance, dependence, and addiction
Tolerance means needing more of a substance for the same effect; physical dependence means the body adapts and withdrawal occurs if it stops; addiction (a substance use disorder) involves compulsive use despite harm. They overlap but are not the same.
Frequently asked questions
What is the difference between MAT and MOUD?
They refer to the same general approach. MAT (Medication-Assisted Treatment) is the older umbrella term; MOUD (Medication for Opioid Use Disorder) is the more current, specific term for using FDA-approved medications alongside counseling.
Is dependence the same as addiction?
No. Physical dependence is the body adapting to a substance so that withdrawal occurs when it stops, which can happen even with prescribed medication. Addiction (a substance use disorder) involves compulsive use despite harm.