Agonist and antagonist drugs work with the neurotransmitters in the brain, but they work in very different ways. They are often used in the treatment for a wide range of conditions, and can be addictive. The way in which you can tell which ones belong in the agonist category, and which ones fall into the antagonist category by the way they interact with the neurotransmitters in the brain.
The neurotransmitters that agonist drugs interact with are naturally found in the brain of a human, and when looking at agonist drugs, there are two main categories. The agonist drug is one that brings about a reaction.
Direct-Binding Agonist - This agonist drug works the same as the neurotransmitters in the brain, and they bind themselves to the site of the receptor. In short, the effect the patient will get when they take it closely mimics what would happen if the drug were to be released directly into the brain.
Classic examples of these direct-binding agonist drugs include nicotine, found in cigarettes and vaping devices, dopamine, and apomorphine.
Indirect-Acting Agonist - This agonist drug enhances the actions that the neurotransmitters have on the brain, encouraging and stimulating release of them, basically upping the amount which are released.
One example of an indirect-acting agonist drug is cocaine.
An antagonist drug will work in the same way, to some extent, as the agonist drug in the sense that it interacts with the neurotransmitters. Where the agonist drug creates an action, the antagonist drug will have the opposite effect - calming the patient down to prevent them from taking the action.
In short, antagonist drugs will block the neurotransmitters, and there are two types:
Direct-Acting Antagonist - The receptors in the brain that would usually be occupied by the neurotransmitters are blocked. The direct-acting antagonist drug basically takes up that space so the neurotransmitters can’t. It means that the connection can’t happen.
One example of a direct-acting antagonist drug is Atropine.
Indirect-Acting Antagonist - This drug stops the release of the neurotransmitters entirely, once again blocking them from working.
One example of an indirect-acting antagonist is Reserpine.
Agonist and Antagonist Drugs - The Differences
Agonist drugs are given their name from the Latin word, “agnista”. This means “contender”. This enhances an action, rather than suppresses it, causing a reaction when the agonist drugs actually bind to the site of the receptor. It works during the time in which the muscles are relaxed, and can also imitate the action of the neurotransmitters in a bid to enhance them.
On the other hand, Antagonist drugs obstruct the path of the neurotransmitters, to stop them rather than enhancing them. They also work during the contraction phase of the muscle. While the agonists are working, the antagonist basically sits back to do nothing, and opposes the reaction. It gets its name from two words - one in Latin and one in Greek. They mean opponent, competitor or rival, which is just what the drug does.