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SCon gressios
Informing the legi
tal Rese rch Service
live debate sice 1914
Updated April 14, 2023
Medications for Opioid Use Disorder
Opioids, such as heroin, fentanyl, and some prescription
pain medications (including morphine and oxycodone) are
substances that act on receptors in the brain important in
regulating pain and emotion. Opioids have high potential
for misuse, dependence, and overdose. The label opioid use
disorder (OUD) is the diagnostic term for a problematic
pattern of opioid use leading to clinically significant
impairment or distress, as defined in the Diagnostic and
Statistical Manual of Mental Disorders (DSM-5-TR).
Medications for Opioid Use Disorder
Research on OUD has generally found that the most
effective treatments involve the use of certain medications.
Three medications are currently used to treat OUD:
methadone, buprenorphine, and naltrexone. Medications for
opioid use disorder (MOUD) are often combined with other
services, such as counseling. (MOUD is also referred to as
medication-assisted treatment [MAT] for OUD.)
Methadone and buprenorphine are both opioids; their use to
treat opioid use disorder is often called opioid substitution
therapy, opioid replacement therapy, or opioid agonist
treatment. These medications can reduce the cravings and
withdrawal symptoms that often accompany
discontinuation of misused opioids, typically without
producing the same euphoria or high as the substances
they replace.
Methadone
Methadone is a full opioid agonist, meaning it binds to and
activates opioid receptors in the brain. Methadone carries
risk of misuse but poses fewer risks of dependence and
overdose than some other full opioid agonists (e.g., heroin).
Methadone suppresses withdrawal symptoms in
detoxification therapy and controls the craving for opioids
in maintenance therapy.
Buprenorphine
Buprenorphine is a partial opioid agonist, meaning it binds
to opioid receptors in the brain and activates them, but not
as much as full opioid agonists. Buprenorphine also carries
risk of misuse but poses fewer risks of dependence and
overdose than full opioid agonists. Like methadone,
buprenorphine is used for detoxification and maintenance
therapy.
Naltrexone
Naltrexone is an opioid antagonist, meaning it binds to
opioid receptors but does not activate them; it prevents
opioid agonists from binding to and activating opioid
receptors. Naltrexone carries no known risk of misuse.
Naltrexone is used for relapse prevention because an
individual on naltrexone who uses opioids will not
experience the effects of those opioids. Naltrexone is
different from naloxone (e.g., Narcan), which is used to
reverse opioid overdose, but not used to treat opioid use
disorders.
Reguiatory Frarmework
Two overlapping systems of federal law apply to MOUD:
one regulating pharmaceuticals and the other regulating
controlled substances.
Federal Food, Drug, and Cosmetic Act (FFDCA)
Under the Federal Food, Drug, and Cosmetic Act (FFDCA,
21 U.S.C. §§301 et seq.), the Food and Drug
Administration (FDA) in the Department of Health and
Human Services (HHS) has primary responsibility for
ensuring the safety and effectiveness of pharmaceuticals,
regardless of whether they are controlled substances. (For
more information, see CRS Report R41983, How FDA
Approves Drugs and Regulates Their Safety and
Effectiveness.) Methadone, buprenorphine, and naltrexone
are subject to the FFDCA.
Controlled Substances Act (CS A)
Under the Controlled Substances Act (CSA, 21 U.S.C.
§§801 et seq.), the Drug Enforcement Administration
(DEA) in the Department of Justice (DOJ) has primary
responsibility for regulating the use of controlled
substances for legitimate medical, scientific, research, and
industrial purposes, and for preventing these substances
from being diverted for illegal purposes. The CSA assigns
various drugs and other substances to one of five schedules
based on accepted medical use, potential for misuse, and
severity of potential psychological or physical dependence.
Schedule I contains substances that have no currently
accepted medical use and are not available by prescription
(such as heroin). Schedules II, III, IV, and V include
substances that have recognized medical uses and are
progressively less dangerous and pose fewer risks. As
shown in Table 1, methadone, buprenorphine, and
naltrexone are classified differently under the CSA. For
more information, see CRS Report R45948, The Controlled
Substances Act (CSA): A Legal Overview for the 118th
Congress.
Table I. FDA-Approved Medications for Opioid MAT
Medication Class CSA Schedule
Methadone Full Opioid Agonist II
Buprenorphine Partial Opioid Agonist III
Naltrexone Opioid Antagonist none
Source: Congressional Research Service based on information
publicly available from FDA and DEA.
Under the CSA, responsibility for regulating schedule II
MOUD (i.e., methadone) falls to both DEA in DOJ and the](ViewImageLocal?handle=hein.crs/govelhi0001&div=1&collection=&method=preview&ext=.png&size=3)