SSRIs vs. SNRIs: 5 Key Differences Between These Antidepressant Classes
Key takeaways:
Selective serotonin reuptake inhibitors (SSRIs) and serotonin and norepinephrine reuptake inhibitors (SNRIs) are two medication classes. They’re often used to treat mental health conditions. Some SNRIs are also approved to treat certain types of pain.
SSRIs and SNRIs share several of the same side effects and drug interactions. But there are a few differences to consider. For example, SNRIs may be more likely to cause dry mouth and increase your blood pressure.
If you have difficulty swallowing pills, some SSRIs come as a liquid or dissolvable tablet. SNRIs are only available as tablets and capsules that you usually have to swallow whole. But certain SNRI capsules can be opened and sprinkled onto soft food.
When deciding between SSRIs and SNRIs, the best choice for you may depend on several factors. Examples include what condition you’re treating, other medications you take, and your preferences.
Table of contents
Selective serotonin reuptake inhibitors (SSRIs) and serotonin and norepinephrine reuptake inhibitors (SNRIs) are both first-choice options for treating depression in adults. They’re also used to treat other mental health conditions, such as anxiety disorders.
While these antidepressant classes may sound similar, there are a few key differences between them. How they work, what they treat, and potential side effects are a few examples. If you’re considering starting an antidepressant — or thinking about changing medications — you may be wondering what these differences can mean for you.
SSRI and SNRI medications
Before diving into the differences between these classes, it’s helpful to know which medications are considered SSRIs and SNRIs. Each class has several options to choose from, as detailed in the table below.
| FDA-approved SSRIs | FDA-approved SNRIs |
|---|---|
|
|
We explore what you should know about five differences between SSRIs and SNRIs below.
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1. SSRIs and SNRIs work in different ways
Serotonin and norepinephrine are two chemicals in the body that are thought to regulate mood. And while the mechanism behind depression and other mental health conditions isn’t fully understood, researchers believe making more of these chemicals available in the brain can play a role in treating them.
SSRIs are thought to work mostly by raising serotonin levels in the brain. They prevent serotonin from being reabsorbed by nerve cells, allowing more of it to be available. SSRIs mainly have this effect on serotonin, which is why they’re called selective serotonin reuptake inhibitors. Vilazodone is an SSRI that also directly acts on serotonin receptors (binding sites).
Similarly, SNRIs raise serotonin levels in the brain by blocking its reuptake. But they also have this effect on norepinephrine, which is why they’re called serotonin and norepinephrine reuptake inhibitors. What’s more, serotonin and norepinephrine also play a role in regulating pain. This is why SNRIs can sometimes have uses beyond mental health conditions.
2. SSRIs and SNRIs have different approves uses
Most SSRIs and SNRIs are approved to treat major depressive disorder. However, there are a few notable differences in other approved uses between each class.
| Approved uses of SSRIs | Approved uses of SNRIs |
|---|---|
|
|
| Note: FDA-approved uses can vary for specific medications in each class. | |
Unlike SSRIs, some SNRIs are approved to treat certain types of pain. Milnacipran and duloxetine are both used to treat fibromyalgia. Duloxetine is also approved to treat diabetes-related nerve pain (diabetic neuropathy) and chronic musculoskeletal pain. So if you have depression or anxiety with chronic pain, an SNRI might be a good option.
Good to know: Despite these differences, SSRIs and SNRIs are often prescribed off-label for certain conditions. For example, an SNRI like venlafaxine may be prescribed for OCD, even though it’s not approved for that use.
3. SSRIs and SNRIs can cause similar, but different side effects
Both SSRIs and SNRIs can cause side effects such as nausea and vomiting, increased sweating, and sexual problems.
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Despite these overlapping side effects, there are a few differences between the two classes. Compared to SSRIs, SNRIs may be more likely to cause dry mouth and nausea. They’re also more likely to cause a rise in blood pressure and heart rate, which may be related to the dose.
SNRIs also tend to be cleared from the body more quickly than SSRIs. Because of this, you may be more likely to experience withdrawal symptoms if you stop taking them abruptly. But this can also vary between medications.
Good to know: There can be some differences between medication side effects in the same class. With SSRIs, for example, paroxetine may be more likely to cause sexual problems, such as erectile dysfunction. This may be less likely with vilazodone.
4. SSRIs and SNRIs can have different drug interactions
Many drug interactions are shared among SSRIs and SNRIs. Both groups of medications can interact with the following medications:
Blood thinners, such as warfarin (Coumadin, Jantoven)
Nonsteroidal anti-inflammatory drugs (NSAIDs), such as naproxen (Aleve, Naprosyn) and ibuprofen (Advil, Motrin)
Medications that raise serotonin levels, including some opioids, migraine medications, and other antidepressants
SSRIs and SNRIs each have their own unique interactions, too. For example, SNRIs may make blood pressure medications such as clonidine less effective. And, although rare, certain SSRIs can lengthen the time it takes your heart to reset between beats, resulting in serious heart rhythm problems. This may be more likely to happen if they’re taken with interacting medications.
Keep in mind: SSRIs and SNRIs also have many other interactions, which can vary by medication. Ask your healthcare provider and pharmacist before starting any new medications or supplements. This helps them screen for potential interactions ahead of time.
5. SSRIs are available in a greater variety of dosage forms
Both SNRIs and SSRIs are available as capsules and tablets. But some SSRIs also come as an oral liquid, which can be a good option if you have trouble taking pills. SSRIs that are available in a liquid form include:
Fluoxetine
Sertraline
Paroxetine
Citalopram
Escitalopram
Additionally, some SSRIs offer other unique dosage forms. For example, citalopram comes as an orally disintegrating tablet. And fluoxetine (Prozac) is available in a once-weekly capsule, which can be a convenient option for some people.
SNRIs don’t come in liquid form. But you can open extended-release venlafaxine (Effexor XR) capsules and sprinkle the contents onto soft foods, such as applesauce, prior to taking. Your pharmacist can tell you if this is an option for your medication and how to do it correctly.
Good to know: Other SNRI capsules, such as duloxetine and levomilnacipran, cannot be opened and must be swallowed whole. Otherwise, your body might not absorb the medication properly.
How to decide between an SSRI and SNRI
There’s no “one-size-fits-all” approach to treating mental health conditions. When choosing between an SSRI and an SNRI, here are a few things to consider:
What condition are you treating? Not all SSRIs and SNRIs are approved for the same conditions, though sometimes they overlap. SNRIs may be a good option if you also need relief from certain types of chronic pain. Your healthcare provider can help you understand which class might work better for you.
Have you taken antidepressants before? If a particular SSRI or SNRI has worked for you in the past, your healthcare provider may want to start there.
Are you taking other medications? Which medications you’re taking could help determine whether an SSRI or SNRI might be a better choice for you. SNRIs and SSRIs share many of the same drug interactions. But they can also interact with some medications differently.
Do you have trouble swallowing pills? SNRIs are only available in tablets and capsules. If you have difficulty taking pills, certain SSRIs are available in a liquid form might be easier for you to take.
Are certain side effects bothering you? SSRIs and SNRIs can cause several of the same side effects, with a few differences. If certain side effects are bothering you, there may be an option in the other class that you may be able to tolerate better.
Within the SSRI and SNRI classes, there are many options to try. It may take time for you and your healthcare provider to find one that works best for you.
The bottom line
SSRIs and SNRIs are antidepressants that are commonly used to treat different mental health conditions. SNRIs are also used to treat certain types of chronic pain. Both classes can cause similar side effects. But dry mouth and increased blood pressure may be more likely with SNRIs.
SSRIs and SNRis can interact with blood thinners, NSAIDs, and other medications that affect serotonin. But some SSRI interactions can increase the risk of heartbeat changes, which can result in serious heart rhythm problems.
When deciding between SSRIs and SNRIs, your healthcare provider may consider several different factors. Examples include what you’re treating, other medications you take, and your preferences.
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References
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For additional resources or to connect with mental health services in your area, call SAMHSA’s National Helpline at 1-800-662-4357. For immediate assistance, call the National Suicide Prevention Lifeline at 988, or text HOME to 741-741 to reach the Crisis Text Line.
