Glossary

Filter terms

Addiction

A treatable brain condition, also called substance use disorder, in which a person continues using a substance despite harm. Different from physical dependence.

Agonist

A drug that activates a receptor. Oxycodone is a full opioid agonist; buprenorphine is a partial agonist.

Antagonist

A drug that blocks a receptor. Naloxone is an opioid antagonist.

Benzodiazepine

A class of sedatives that enhance GABA, such as alprazolam and diazepam.

Boxed warning

The FDA's strongest label warning, printed in a black box at the top of the prescribing information.

CNS depressant

Any substance that slows the central nervous system, including opioids, sedatives, alcohol, and GHB. Combining them is a leading cause of overdose.

Contingency management

A treatment that gives rewards for drug-free tests. The most effective treatment for stimulant use disorder.

Controlled substance

A drug regulated under the Controlled Substances Act and placed in one of five schedules.

CYP3A4 and CYP2D6

Liver enzymes that break down many drugs. Medicines that block or speed them up can raise or lower drug levels.

DEA registration

Federal registration a clinician needs to prescribe controlled substances.

Dependence (physical)

The body's adaptation to a drug, so that stopping causes withdrawal. It can happen with prescribed use and is not the same as addiction.

Dissociative

A drug, such as ketamine or PCP, that causes feelings of detachment from the body and surroundings.

Fentanyl test strip

A paper strip that detects fentanyl in a drug sample. Legal in most states.

Half-life

The time it takes for the level of a drug in the blood to fall by half. After about five half-lives, most of a drug is gone.

Harm reduction

Practical strategies, such as naloxone, test strips, and syringe services, that reduce the harms of drug use.

Naloxone

A medicine that rapidly reverses opioid overdose. Sold without a prescription as Narcan and generics.

Nitazenes

A class of synthetic opioids, some stronger than fentanyl, found in counterfeit pills.

Opioid use disorder

Addiction to opioids. Treated most effectively with buprenorphine or methadone.

PDMP

Prescription drug monitoring program: a state database of controlled-substance prescriptions that clinicians and pharmacists check.

Precipitated withdrawal

Sudden withdrawal caused by taking buprenorphine or naloxone while full opioids are still active.

Prodrug

An inactive drug that the body converts into an active one, such as lisdexamfetamine to dextroamphetamine, or codeine to morphine.

REMS

Risk Evaluation and Mitigation Strategy: an FDA safety program that restricts how certain drugs are prescribed or dispensed.

Schedule

One of five categories in the Controlled Substances Act, from Schedule I (no accepted medical use) to Schedule V (lowest potential for abuse).

Serotonin syndrome

A dangerous excess of serotonin, causing agitation, fever, sweating, muscle twitching, and fast heartbeat, often from combining serotonergic drugs.

Taper

A gradual dose reduction to stop a medicine safely and minimize withdrawal.

Telemedicine flexibilities

Temporary federal rules allowing controlled medicines to be prescribed after a video or phone visit, extended through December 31, 2026.

Tolerance

Needing more of a drug to get the same effect. Tolerance falls after a break, which raises overdose risk.

Xylazine

A veterinary sedative found in illicit fentanyl that is not reversed by naloxone and causes severe wounds.