An agonist is a drug or medication that attaches to and activates specific receptors in order to stimulate drug actions or effects. Agonist Opioids are referred to as either full opioid agonists or partial opioid agonists.
Full opioid agonists are a drug or medication that stimulates activity at opioid receptors in the central nervous system that are normally stimulate by naturally occurring opioids. Examples of full opioid agonists include:
Partial opioid agonists also stimulate activity at opioid receptors but do not produce the same maximal effects as a full opioid agonist; as with full opioid agonists, this activity occurs at receptors that are normally stimulated by naturally occurring opioids. Under appropriate conditions, partial agonists can produce effects similar to either agonists or antagonists. An example of a partial opioid agonists is buprenorphine.
In the treatment of chronic opiate addiction, an opiate agonist can be used as maintenance therapy. Opiate medications, often used for pain relief or cough suppression, can be habit forming and in some cases highly addicting, with addiction levels skyrocketing in recent years.