Partial opioid agonists have mixed or limited action when they bind to your opioid receptors. So, doctors often use them to treat opioid use disorder.
Protein receptor sites are like keyholes on the surfaces of your cells. Only proteins of a certain size and shape can bind at a receptor site, acting like a key to unlock the functions of the cell.
Among these receptor sites are opioid receptors on the cells of your nervous system. They wait for your natural opioids, known as endogenous opioids, or opioids introduced into your body, known as exogenous opioids.
Partial opioid agonists bind to opioid receptor sites but don’t generate a full response. In some cases, they may activate one receptor site and suppress another.
When people refer to opioids, they usually refer to full opioid agonists like:
These substances bind to your opioid receptor sites and generate the maximum opioid effect. Some work faster than others, which can greatly impact their effects.
Methadone, for example, is a full opioid agonist. Due to its slow receptor activation, however, it doesn’t result in euphoria like many other full agonists. It still produces the same effects as other full opioid agonists but spread over a longer time.
Partial opioid agonists produce lower opioid effects in general, but their effects can also vary, depending on their dose.
Examples of partial opioid agonists include:
- buprenorphine
- butorphanol
- tramadol
Opioid receptors are involved in many bodily functions. They most commonly link with your capacity to manage pain, but opioid receptors also cue functions related to:
- stress management
- mood regulation
- behavior repetition
The role of opioid receptors in the body’s reward system is why opioid use can result in substance use disorders and drug dependency.
There are five types of opioid receptors in your body involved in different biological responses. The main ones are mu, kappa, and delta.
Partial opioid agonists can act on any opioid receptor. Unlike a full agonist, which can cue a cell to produce the maximum opioid effect, partial agonists can only produce certain or limited effects.
A partial agonist may provide some pain relief, for example, but might not produce euphoria.
Opioid agonists vs. antagonists
Opioid antagonists are substances that can fit into an opioid receptor site without causing the cell to respond. By taking up the opioid receptor, they block opioid agonists or partial agonists from binding to the cell.
Used primarily for reversing opioid overdoses and treating substance use disorders, opioid antagonists can prevent your cells from responding to opioids.
Doctors use partial opioid agonists for pain management and treating opioid use disorder.
Partial agonists offer several benefits for managing opioid use disorder, including reducing withdrawal symptoms and the risks of overdosing or returning to opioid misuse.
Buprenorphine, for example, is a partial opioid agonist used in medical pain management and as a treatment drug for opioid use disorder. It has a partial effect on the mu receptor and,
When used to treat opioid use disorder, buprenorphine (Subutex) has a “ceiling effect.” You won’t experience any additional effects if you take more than prescribed. This not only reduces the likelihood of misuse but also reduces the risk of an overdose.
Suboxone, which is a combination of buprenorphine and naloxone, an opioid antagonist, produces a similar effect and is used to treat opioid use disorder.
Partial opioid agonists are substances that produce opioid responses in your cells but at a lesser capacity than full agonists.
If you’re living with opioid use disorder, partial opioid agonists may be a part of your treatment program. They can help relieve withdrawal symptoms by satisfying cravings and reducing physical discomfort without the dependency effects that can come from full agonists.