From the Guidelines
An antagonist is a substance or drug that blocks or inhibits the action of another substance, typically by binding to a receptor without activating it, as seen with naloxone, which antagonizes mu, kappa, and delta opioid receptors 1. In pharmacology, antagonists work by preventing natural chemicals or medications (agonists) from producing their normal effects.
- They can be competitive, like naloxone, which competes with and displaces narcotics at the opiate receptor 1.
- The effectiveness of an antagonist depends on its binding affinity and selectivity, with higher affinity and selectivity generally leading to more effective blockade of the target receptor.
- Antagonists are valuable therapeutic tools because they can stop or reduce unwanted biological processes, such as reversing opioid overdoses with naloxone 1.
- Understanding antagonists is crucial for developing medications that can precisely control biological functions by blocking specific pathways in the body. Key characteristics of antagonists, such as their duration of action and route of administration, are important considerations in clinical practice, as seen with naloxone, which can have a duration of action ranging from 45 minutes to 3-4 hours depending on the dose and route of administration 1.
From the FDA Drug Label
Naloxone hydrochloride injection, USP, an opioid antagonist, is a synthetic congener of oxymorphone. Rx only Opioid Antagonist
An antagonist is a type of drug that opposes the action of another drug. In the case of naloxone, it is an opioid antagonist, meaning it counteracts the effects of opioids.
- Key characteristics: Naloxone hydrochloride is a synthetic congener of oxymorphone and is used to reverse the effects of opiates.
- Main use: To counteract acute opioid poisoning and reverse opioid depression 2, 2, 2.
From the Research
Definition of an Antagonist
- An antagonist is a type of ligand that binds to a receptor and reduces or blocks the action of an agonist, a molecule that normally binds to the receptor and triggers a response 3.
- In the context of beta-adrenergic receptors, beta-blockers are a type of antagonist that competes with endogenous catecholamines for binding to the receptor, thereby reducing the receptor's activity 4, 5.
Characteristics of Antagonists
- Antagonists can have different levels of selectivity for specific receptor subtypes, which can affect their efficacy and side effect profile 6.
- Some antagonists, such as beta-blockers, can have additional properties, such as vasodilating effects, that can influence their therapeutic effects 7, 5.
- Antagonists can also have different mechanisms of action, such as competitive antagonism, which involves competing with the agonist for binding to the receptor, or non-competitive antagonism, which involves reducing the receptor's activity through a different mechanism 3.
Examples of Antagonists
- Beta-blockers, such as propranolol and bisoprolol, are examples of antagonists that are used to treat cardiovascular diseases, such as hypertension and heart failure 4, 5.
- Inverse agonists, which are a type of antagonist that can reduce the constitutive activity of a receptor, are also being studied for their potential therapeutic effects 3.