Opioids are a class of drugs that act on opioid receptors in the brain. Signals sent to these receptors can block pain and lead to feelings of euphoria.

Different types of opioids differ in a few key ways: the form of the drug (i.e. powder, tar, pill, liquid, etc.), how potent they are, how long their effects last and their potential for addiction. Whether or not a particular opioid is regulated and produced in a standardized manner also impacts its potency and safety.

Morphine is a naturally occurring substance derived from the opium poppy plant often used to alleviate pain and other physical ailments. The U.S. classifies it in Schedule II, which means the federal government has determined that it has potential for misuse and dependence, but also has accepted medical use and can be prescribed to patients.

Heroin is processed from morphine. It is classified as a Schedule I substance, which means the federal government has determined that it has no currently accepted medical use. However, heroin (diacetylmorphine) is available medically in some limited circumstances, particularly in Europe and Canada. In the U.S., almost all heroin comes from the unregulated market.

Oxycodone and Hydrocodone are semisynthetic opioids derived from the opium poppy plant, are chemically similar to morphine and are used to treat acute and chronic pain. Unlike illicitly produced heroin, their production is regulated, which means they have consistent effects and can be made available in specified doses. OxyContin is a controlled release form of oxycodone so it is released gradually over a period of time. Oxycodone and hydrocodone are Schedule II substances, which means that the federal government has determined that it has accepted medical use.

Fentanyl is one of the most powerful opiate-based painkillers, used to treat chronic pain patients who have developed a resistance to other less powerful opiates such as morphine or oxycodone. Its effects are active at much lower doses than other opiates, so its non-medical use is riskier due to its increased potency. Like morphine, fentanyl is a Schedule II substance. In recent years, much of the U.S. heroin supply has been mixed with synthetically created illegal fentanyl, leading to skyrocketing overdose death rates. Illegal fentanyl is not regulated and is often mixed into heroin, with or without the user’s knowledge, which has led to increased overdose deaths since 2013.

Methadone and Buprenorphine are opioids that have been approved by the U.S. Food and Drug Administration (FDA) as medications to treat opioid dependence. They act on same receptors in the brain as other opioids.

See the fact sheet for more information and sources.