Mental Health: Classifying antidepressants

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Ailey O’Toole
   Staff Writer

Antidepressants are the most popular form of treatment for depression and anxiety disorders. While they may not cure depression, the medicines will certainly help to alleviate symptoms.

What most people don’t know is that there are many different types of antidepressants that act on different neurotransmitters in the brain. These medicines are prescribed based on what symptoms the patient is experiencing and what neurotransmitter is most likely not working properly.

A neurotransmitter is a chemical substance that is released at the end of a nerve by the arrival of a nerve impulse and, by diffusing across the synapse, causes the transfer of the impulse to another nerve fiber.

Basically, neurotransmitters are brain chemicals that communicate information throughout our brains by travelling from one nerve cell to another.

There are three neurotransmitters that are most often associated with depression: serotonin, norepinephrine and dopamine.

Serotonin is known to regulate mood stability; dopamine is responsible for our drive or desire to get things done; and norepinephrine is responsible for the fight-or-flight response. Depleted levels of any of these can cause many of the symptoms that accompany depression.

There are five main types of antidepressants. Three of them are referred to as “reuptake inhibitors.” Reuptake is the process in which neurotransmitters are reabsorbed back into nerve cells in the brain after they have been released to send messages between nerve cells. A reuptake inhibitor prevents this absorption from happening. Instead of getting reabsorbed, the neurotransmitter stays in the gap between the nerves, called the synapse, for a longer amount of time.

The reason reuptake inhibitors do this is because we feel the effects of neurotransmitters when they are in the synapse.

So, preventing the reabsorption of these chemicals allows people with depression to experience the effects of serotonin, dopamine, and norepinephrine for a longer amount of time, hopefully increasing communication between nerve cells and strengthening pathways in the brain that regulate mood.

The three types of reuptake inhibitors are selective serotonin (SSRI), serotonin and norepinephrine (SNRI) and norepinephrine and dopamine (NDRI).

As you can tell by the names, each medicine targets a different type of neurotransmitter. SSRIs are the most common and include Prozac, Paxil, Zoloft, Celexa and Lexapro. Cymbalta, Effexor and Pristiq are all SNRIs. Wellbutrin and Aplenzin fall into the category of NDRIs.

Atypical antidepressants are medicines that don’t fit neatly into any other categories. They include trazodone, Remeron and Brintellix. They are all sedating medicines and are usually taken in the evening.

These medicines act in two ways: first, they prevent the reuptake of serotonin, same as SSRIs and SNRIs, and second, they prevent serotonin that is released in a synapse from binding at certain receptors and instead, redirect them to other receptors that can help mood circuits function better. These drugs are sometimes also called serotonin antagonist and reuptake inhibitors (SARIs).

Older drug classes include tricyclic antidepressants (TCAs) and monoamine oxidase inhibitors (MAOIs). TCAs work by blocking the reabsorption of serotonin, like SSRIs and SNRIs, but they act on epinephrine as well. Epinephrine is commonly referred to as adrenaline and regulates stress responses. TCAs include Elavil, Norpramin,and Pamelor.

MAOIs work a little differently than other antidepressants. Monoamine oxidase is a natural enzyme that breaks down serotonin, epinephrine and dopamine. MAOIs block the process of this enzyme so that those neurotransmitters are not broken down and their effects get a boost.

The downside is that MAOIs also prevent the body from breaking down other medicines metabolized by the enzyme, raising the risk of high blood pressure. Emsam, Marplan and Nardil are all types of MAOIs.

These two classes of drugs are not often prescribed anymore because they are known to cause some pretty nasty side effects.

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