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How Different Antidepressants Work

If you have treatment-resistant depression, you might have already picked up some of the antidepressant drug lingo -- you know your SSRIs, your SNRIs and your MAOIs. But do you really know how  these drugs help?

If you don't, you're not alone. The truth is that even experts aren't really sure how antidepressants work. There's just a lot we don't know about how the brain functions.

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The most important thing you need to know when you’re living with treatment-resistant depression is that antidepressants often can help. To help you understand all your medication options, here are the facts about different types of antidepressants -- along with some tips on how to use them most effectively.

Understanding Antidepressants: Basic Brain Chemistry

If you've read up on antidepressants -- in newspapers and magazines, or on the Web -- you might see depression explained simply as a "chemical imbalance" or a "serotonin deficiency." Unfortunately, it's not that simple. We really don't know what causes depression or how it affects the brain. We don't exactly know how antidepressants improve the symptoms.

That said, many researchers believe that the benefits of antidepressants stem from how they affect certain brain circuits and the chemicals (called neurotransmitters) that pass along signals from one nerve cell to another in the brain. These chemicals include serotonin, dopamine, and norepinephrine.  In various ways, different antidepressants seem to affect how these neurotransmitters behave. Here's a rundown of the main types of antidepressants.

 

Reuptake Inhibitors: SSRIs, SNRIs, and NDRIs

Some of the most commonly prescribed antidepressants are called reuptake inhibitors. What's reuptake? It's the process in which neurotransmitters are naturally absorbed back into nerve cells in the brain. A reuptake inhibitor prevents this from happening. Instead of getting reabsorbed, the neurotransmitter stays -- at least temporarily -- in the gap between the nerves, called the synapse.

What's the benefit? The basic theory goes like this: keeping levels of the neurotransmitters higher could improve communication between the nerve cells -- and that can strengthen circuits in the brain which regulate mood.

Different kinds of reuptake inhibitors target different neurotransmitters. There are three types: 

  • Selective serotonin reuptake inhibitors (SSRIs) are some of the most commonly prescribed antidepressants available. They include Celexa, Lexapro, Luvox, Paxil, Prozac, and Zoloft. Another drug, Symbyax, is approved by the FDA specifically for treatment-resistant depression. It’s a combination of the SSRI antidepressant fluoxetine (Prozac) and another drug approved for bipolar disorder and schizophrenia called olanzapine (Zyprexa). Abilify and Seroquel have been FDA approved as add-on therapy to antidepressants for treatment-resistant depression. Plus, doctors often use other drugs in combination for treatment-resistant depression. Also, the drug Viibryd was approved in early 2011. It's an SSRI but affects serotonin in two ways to relieve major depression.
  • Serotonin and norepinephrine reuptake inhibitors (SNRIs) are among the newer types of antidepressant. As the name implies, they block the reuptake of both serotonin and norepinephrine. They include Cymbalta, Effexor, Khedezla, Fetzima, and Pristiq.
  • Norepinephrine and dopamine reuptake inhibitors (NDRIs) are another class of reuptake inhibitors, but they're represented by only one drug: Wellbutrin. It affects the reuptake of norepinephrine and dopamine. 

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