Types of Opioids

Opioid medications work by mimicking endorphins—chemicals in the brain that act as the body’s natural pain relievers. While all opioids work similarly, they can be categorized many different ways. Distinctions are often made:

  • By the way they are made (e.g. natural vs. synthetic)
  • By the way they are used and affect people, and
  • How they are taken (e.g. oral pill vs. skin patch)

Once in the bloodstream, opioid molecules bind to receptors on the end of nerves throughout the body and prompt them to either suppress or prompt a reaction. Read How Opioids Work in the Brain

This page discusses these distinctions and what they might mean to prescribers and people taking opioids.

Natural vs. Synthetic Opioids

The term opioid includes drugs that are derived—naturally and semi-synthetically—from the opium poppy plant. In addition, some opioids are called synthetic because they are produced in a lab.

  • Naturally derived opioids can be extracted directly from the poppy plant. Examples of these drugs include codeine and morphine.
  • Semisynthetic opioids are a hybrid and go through some laboratory chemical modifications, such as hydrocodone (Vicodin) and oxycodone (Percocet).
  • Synthetic opioids are entirely laboratory manufactured to mimic the chemical makeup of natural opioids. An example of this is fentanyl (Duragesic), typically used for cancer pain.

The illegal drug heroin is an opioid derived from morphine, a natural opioid. Illegal drug products called synthetic heroin also exist.


Schedule of Opioids

Pharmacists and other medical professionals often refer to drugs according to their “Schedule” classification. A drug’s Schedule classification is determined by the Drug Enforcement Agency (DEA) and is dependent upon its potential for abuse, likelihood of dependence, as well as medical use.

  • Schedule I drugs, such as heroin, have the highest potential for abuse and have no medical purpose.1
  • Schedule II drugs, such as codeine, hydrocodone, and fentanyl, have a high potential for abuse and psychological and physical dependence.1
  • Schedule III drugs have less potential for abuse than Schedule I and II but can still lead to psychological and physical dependence. Examples of schedule III drugs include buprenorphine, naloxone, and Tylenol with codeine.1
  • Schedule IV drugs, such as tramadol, have a low potential for abuse compared to drugs in schedule III, however, they can still lead to physical or psychological dependence.1
  • Schedule V drugs, such as Robitussin AC, have the lowest potential for abuse and limited physical or psychological dependence.1

The schedule of drug usually relates to its formulation; synthetic drugs usually carry a higher risk of addiction.

Opioid Delivery Methods

Opioids typically come in a variety of formulations, some used for specific circumstances.

  • Tablets and capsules. The most common forms of opioids are tablets and capsules that are swallowed. The medication passes through the digestive system and then enters the bloodstream.
  • Skin patches. Patches deliver opioids, usually fentanyl or Buprenorphine (Butrans), systematically through absorption via the skin.
  • Oral liquids. Opioids, such as oxycodone and morphine, are sometimes available in liquid form. Generally, oral liquid opioids are prescribed for people who are in the hospital or hospice care, or who have trouble swallowing pills.
  • Oral transmucosal lozenges. Opioid lozenges (Actiq) are designed like a lollipop. Typically reserved for cancer pain, the medication is delivered through the mucus membrane under the tongue.
  • Intrathecal pain pump. A pain pump is a device implanted under the skin that can deliver small amounts of opioids via a catheter into spinal fluid.
  • Injections. Injectable opioids, such as morphine, are occasionally given for pain control in a hospital setting.
  • Nasal sprays. Naloxone (Narcan), used to reverse opioid overdoses, is available in a nasal spray and can be obtained in a pharmacy without a prescription in most states.

Doctors, nurses, hospice workers and patients must communicate with one another to help ensure that a medication’s delivery method is appropriate for the patient. For example, if a patient has a difficult time swallowing an opioid tablet, or if an opioid skin patch leaves skin irritated, the prescribing doctor should be notified.


  • 1.Drug Scheduling. Drug Enforcement Agency Website. Accessed April 11 2018.