What receptor do partial agonists bind to?

From the Guidelines

Partial agonists, such as buprenorphine, bind to the μ-opioid receptor. This is based on the most recent and highest quality study available, which states that buprenorphine is a partial opioid agonist with a high binding affinity for the μ-opioid receptor 1.

Key Points

• Buprenorphine's high affinity for the μ-opioid receptor diminishes the ability of other more potent full agonist opioids to dislodge it from the receptor 1.
• The binding of partial agonists to their respective receptors results in a reduced maximum response even at saturating concentrations.
• Partial agonists can act as functional antagonists in the presence of high concentrations of full agonists while providing some receptor activation when full agonist levels are low.
• The unique properties of partial agonists make them valuable in clinical settings where complete receptor blockade would cause adverse effects, but some receptor stimulation is beneficial.

Receptor Binding

The μ-opioid receptor is the primary target for buprenorphine, and its binding affinity is high, allowing it to compete effectively with endogenous ligands 1.

Clinical Implications

The use of partial agonists like buprenorphine can reduce the risks of overdose and dependence in certain drug classes due to their ceiling effect 1.

Comparison with Other Studies

Another study also confirms that buprenorphine is a partial agonist of mu opioid receptors 1. However, the most recent and highest quality study available is 1, which provides more detailed information on the binding affinity and clinical implications of buprenorphine.

From the FDA Drug Label

Buprenorphine Sublingual Tablets contain buprenorphine, a partial agonist at the mu-opioid receptor and an antagonist at the kappa-opioid receptor. Buprenorphine is a partial agonist at the mu-opioid receptor and chronic administration produces physical dependence of the opioid type, characterized by withdrawal signs and symptoms upon abrupt discontinuation or rapid taper.

Partial agonists bind to the mu-opioid receptor. 2 2

• Key points:
  • Buprenorphine is a partial agonist at the mu-opioid receptor.
  • It also acts as an antagonist at the kappa-opioid receptor.

From the Research

Receptor Binding of Partial Agonists

• Partial agonists bind to various receptors, including the μ-opioid receptor, δ-opioid receptor, κ-opioid receptor, and opioid receptor-like 1 receptor 3, 4, 5
• Buprenorphine, a partial agonist, has a high binding affinity for the μ-opioid receptor, but low efficacy, resulting in a partial effect upon binding 3, 4, 5
• Partial agonists can act as antagonists by competing for receptor binding with full agonists, and their level of activity depends on the level of endogenous receptor activity 6

Specific Receptors Bound by Partial Agonists

• μ-opioid receptor: buprenorphine is a partial agonist with high binding affinity, but low efficacy 3, 4, 5
• δ-opioid receptor: buprenorphine is an antagonist with high binding affinity 3
• κ-opioid receptor: buprenorphine is an antagonist with high binding affinity 3
• Opioid receptor-like 1 receptor: buprenorphine is an agonist with low binding affinity 3, 5

Implications of Partial Agonist Binding

• Partial agonists can provide a unique role in mediating analgesic signaling at spinal opioid receptors while having less of an effect on brain receptors, potentially limiting classic opioid-related adverse events 3
• Partial agonists can be used to treat patients with addiction and decrease the symptoms of withdrawal and risks of overdose and intoxication 4, 6