SSRI vs. SNRI Medications: What’s the Difference?

SSRIs and SNRIs are two commonly prescribed types of antidepressants used to treat conditions like depression and anxiety. While they have similarities, they affect different brain chemicals and can differ in their uses and potential side effects.

So, what’s the difference between SSRIs and SNRIs, and how does a psychiatrist decide which one to prescribe? Understanding how these medications work can help you have more informed conversations with your provider. If you’re exploring medication options, working with a trusted psychiatrist in Chicago can help you find an approach that fits your individual needs.

Keep reading to learn how SSRIs and SNRIs work, what they’re commonly used to treat, their potential side effects, and the key differences between them.

Key Takeaways:

• Selective Serotonin Reuptake Inhibitors (SSRIs) are a drug class and type of antidepressant. They work by stopping your brain from absorbing serotonin too quickly, which means that more serotonin is available to help with mood and cell communication in the brain.
• Selective Serotonin Norepinephrine Inhibitors (SNRIs) are another drug class. They’re different from SSRIs because they act on both norepinephrine and serotonin.
• The fact that SNRIs act on both norepinephrine and serotonin is one of the major factors that distinguishes how SSRIs vs. SNRIs work. It influences the most likely side effects and which one your psychiatrist is more likely to suggest.
• Despite working on the same chemicals, every SSRI and every SNRI is different. Everyone responds to each medication uniquely. Working with a psychiatrist you trust and trial and error can help you find the right fit.

What Are SSRI Drugs?

SSRIs (selective serotonin reuptake inhibitors) are a class of antidepressant medication. They are commonly used to treat depression and are considered a first-line pharmacological treatment for depression and several other mental health conditions.[1] Common SSRIs include:

• Fluoxetine (Prozac)
• Sertraline (Zoloft)
• Escitalopram (Lexapro)
• Citalopram (Celexa)
• Paroxetine (Paxil)

SSRIs primarily work by blocking the reuptake of serotonin, making more serotonin available between nerve cells in the brain. Serotonin is a neurotransmitter involved in functions such as mood, sleep, and digestion.

SSRIs don't work immediately. Some people may begin noticing improvements within a few weeks, but it can take several weeks to experience their full therapeutic effects.

What Are SNRI Drugs?

SNRIs (serotonin-norepinephrine reuptake inhibitors) also affect serotonin. Unlike SSRIs, however, they affect both serotonin and norepinephrine.[2] Common SNRIs include:

• Duloxetine (Cymbalta)
• Desvenlafaxine (Pristiq)
• Venlafaxine (Effexor)
• Levomilnacipran (Fetzima)

Milnacipran (Savella) is another SNRI, but in the United States, it is FDA-approved for the treatment of fibromyalgia rather than depression.

Norepinephrine is a neurotransmitter involved in functions such as attention, alertness, and the body's response to stress. By keeping serotonin and norepinephrine active for longer, SNRIs can help improve mood and, in some cases, ease pain signals. Some SNRIs are also used to treat certain types of chronic pain. Like SSRIs, SNRIs may take several weeks to provide their full therapeutic effects.

SSRI vs. SNRI: What’s the Difference?

On a foundational level, the main difference between SSRIs and SNRIs is which neurotransmitters they primarily affect.

• SSRIs primarily affect serotonin. They work by blocking the reuptake, or reabsorption, of serotonin, making more of it available between nerve cells in the brain.
• SNRIs affect both serotonin and norepinephrine. Like SSRIs, they block the reuptake of these neurotransmitters, making more of them available between nerve cells.

This difference can influence what conditions and symptoms each medication may be used to treat. However, even within these two drug classes, each SSRI and SNRI is different. Your provider will consider the specific medication, your symptoms, potential side effects, your health history, and other factors when determining which option may be appropriate.

Which Conditions Do SSRIs and SNRIs Treat?

SSRIs and SNRIs are commonly used to treat depression and anxiety disorders, but medications within these classes can be used for several other mental and physical health conditions. Depending on the specific medication, these may include both FDA-approved and off-label uses.

FDA-approved uses of certain SSRIs include:

• Major depressive disorder (MDD)
• Generalized anxiety disorder (GAD)
• Social anxiety disorder
• Obsessive-compulsive disorder (OCD)
• Post-traumatic stress disorder (PTSD)
• Panic disorder
• Bulimia nervosa

FDA-approved uses of certain SNRIs include:

• Major depressive disorder (MDD)
• Generalized anxiety disorder (GAD)
• Social anxiety disorder
• Panic disorder
• Fibromyalgia
• Diabetic peripheral neuropathic pain
• Chronic musculoskeletal pain

Not every SSRI or SNRI is approved or used to treat every condition on these lists. Each medication has its own FDA-approved uses, and your provider will consider your diagnosis, symptoms, health history, and other factors when choosing a medication.

Some SSRIs and SNRIs may also be prescribed off-label, meaning a provider prescribes the medication for a condition that is not specifically included in its FDA-approved labeling. For example, certain medications may be prescribed off-label for concerns like IBS or menopause-related hot flashes, with some of these uses supported by research.[3]

Side Effects of SSRIs vs. SNRIs

SSRIs and SNRIs can cause some similar side effects, including nausea, changes in appetite or weight, dry mouth, changes in sleep or energy levels, headaches, sweating, and sexual side effects. Some side effects may improve as your body adjusts to the medication.

Because SNRIs also affect norepinephrine, some may be more likely to affect blood pressure and heart rate, particularly at certain doses. Potential SNRI side effects can include:

• Increased blood pressure
• Increased heart rate
• Nausea
• Dry mouth
• Increased sweating
• Dizziness
• Sleep changes

Both SSRIs and SNRIs can also cause discontinuation symptoms if they are stopped too quickly, although the likelihood and severity can vary depending on the specific medication, dose, and other factors. This is why you should talk to your prescribing provider before stopping or changing your medication.

Some people tolerate SNRIs better than SSRIs or vice versa. However, side effects often depend more on the specific medication, dose, and individual response than whether the medication is an SSRI or SNRI. Your provider can help you weigh potential side effects against the expected benefits when choosing a medication.

How Psychiatrists Choose Between an SSRI and SNRI

Since people can respond differently to medications, how do psychiatrists decide which one to prescribe? When choosing between an SSRI and SNRI, psychiatrists may consider:

• Diagnosis: SSRIs and SNRIs have different FDA-approved and off-label uses. Your diagnosis and the symptoms being treated can help your psychiatrist determine which medications to consider.
• Symptom profile: Even people with the same diagnosis can experience very different symptoms. For example, one person with depression may experience insomnia and significant anxiety, while another may struggle with oversleeping and low energy. Your specific symptoms can help your psychiatrist narrow down medication options.
• Potential side effects: If you’re particularly concerned about a certain side effect, such as sexual dysfunction or excessive sweating, your psychiatrist can consider the side-effect profiles of individual medications when discussing your options.
• Medical conditions: Your physical health can also influence medication choices. For example, if you have high blood pressure, your psychiatrist may take into account that some SNRIs can increase blood pressure.[4] On the other hand, certain SNRIs, such as duloxetine (Cymbalta), are also approved to treat conditions like fibromyalgia and certain types of chronic pain.
• Other medications: Your psychiatrist will consider other prescription medications, over-the-counter medications, and supplements you take to identify potential interactions and help determine which options may be appropriate.
• Pharmacogenetic testing: In some cases, psychiatrists may use pharmacogenetic testing to provide additional information about how genetic differences could affect the way your body processes certain medications. However, these tests cannot definitively predict which antidepressant will work best for you and are only one piece of information a provider may consider.
• Your medication history: If you’ve taken an SSRI, SNRI, or another psychiatric medication before, tell your provider how well it worked and any side effects you experienced. Your past response can help inform future treatment decisions.

It’s important to remember that two medications within the same drug class can affect the same person differently. For example, someone may respond well to Cymbalta with few side effects but have a very different experience with Effexor, or vice versa. Finding the right medication can take time, which is why ongoing communication with your prescribing provider is an important part of medication management.

Which Medication Is Right for You?

There isn’t one SSRI or SNRI that is right for everyone. Finding the right medication is an individualized process that you’ll work through with your psychiatrist. Your psychiatrist will consider your symptoms, diagnosis, medical and mental health history, previous medication experiences, other medications you take, and potential side effects when deciding what to try.

Once you start a medication, you’ll continue to work with your psychiatrist to see how you respond. This includes discussing whether your symptoms are improving, any side effects you experience, and other changes you notice. Your psychiatrist can then make adjustments when needed, such as changing your dose or trying a different medication.

Some trial and error can be a normal part of finding the right medication. Staying in communication with your psychiatrist throughout the process can help you find a medication and treatment plan that works well for your individual needs.

Psychiatric Medication Management in Chicago

Finding a psychiatrist you trust matters, especially when you’re starting a new medication or trying to find one that works well for you. At Clarity Clinic, our psychiatric providers take the time to understand your symptoms, treatment history, and individual needs.

Through ongoing psychiatric medication management, we’ll work with you to monitor how your medication is working, address concerns or side effects, and make adjustments when needed.

We offer in-person psychiatric medication management at our Chicagoland clinics, as well as online psychiatry appointments for people throughout Illinois.

Whether you’re looking for psychiatry, therapy, PHP/IOP, or advanced treatment options like TMS for depression or OCD in Chicago, Clarity Clinic is here to help you find the care that fits your needs.

References

[1] Chu, A. (2023, May 1). Selective serotonin reuptake inhibitors. StatPearls [Internet]. https://www.ncbi.nlm.nih.gov/books/NBK554406/

[2] Sansone, R. A., & Sansone, L. A. (2014, March). Serotonin norepinephrine reuptake inhibitors: A pharmacological comparison. Innovations in clinical neuroscience. https://pmc.ncbi.nlm.nih.gov/articles/PMC4008300/

[3] Stubbs, C., Mattingly, L., Crawford, S. A., Wickersham, E. A., Brockhaus, J. L., & McCarthy, L. H. (2017, June 23). Do ssris and snris reduce the frequency and/or severity of hot flashes in menopausal women. The Journal of the Oklahoma State Medical Association. https://pmc.ncbi.nlm.nih.gov/articles/PMC5482277/

[4] Zhong, Z., Wang, L., Wen, X., Liu, Y., Fan, Y., & Liu, Z. (2017a, November 7). A meta-analysis of effects of selective serotonin reuptake inhibitors on blood pressure in depression treatment: Outcomes from placebo and serotonin and noradrenaline reuptake inhibitor controlled trials. Neuropsychiatric disease and treatment. https://pmc.ncbi.nlm.nih.gov/articles/PMC5683798/