Their inclusion does not guarantee they will be prescribed to any individual, as treatment decisions are ultimately at the discretion of healthcare providers. Healthcare providers may prescribe other medications or recommend non-pharmacological treatment based on the patient’s unique health circumstances and needs. Read more
All antidepressants, including SSRIs and SNRIs, carry an FDA boxed warning regarding an increased risk of suicidal thoughts and behaviors in individuals under age 25. Therefore, these age groups are monitored very closely during the early phase of their treatment.
Highlights
- SSRIs and SNRIs are types of antidepressants commonly prescribed to treat depression and anxiety disorders.
- SSRIs selectively inhibit serotonin reuptake, while SNRIs inhibit the reuptake of both serotonin and norepinephrine, increasing their availability in synapses.
- Choosing an SSRI vs an SNRI as a treatment option depends on the person’s diagnosis, medical history, and medication side effects.
SSRIs (selective serotonin reuptake inhibitors) and SNRIs (serotonin-norepinephrine reuptake inhibitors) are the two most commonly prescribed antidepressant medications used to treat mood disorders and anxiety. They work by increasing levels of the brain’s chemical messengers, also called neurotransmitters, in the gaps between nerves.
Despite their many similarities, there are vital differences in how SSRIs and SNRIs work, what they’re used for, their side effects, and drug interactions.
This article will give you all the information you need to chat with your healthcare provider about whether an SSRI or SNRI might be more suitable for you.
SSRI vs SNRI Antidepressants: Differences and Similarities
Let’s start by looking at their similarities and differences. Some hints are in their class names: “selective serotonin reuptake inhibitors” and “serotonin and norepinephrine reuptake inhibitors”. However, there are more nuances.
Similarities Between SSRIs and SNRIs
Both SSRIs and SNRIs are:
- ‘Reuptake inhibitors’, so they act in the same basic way
- Commonly used to treat depression and anxiety disorders
- Slow-acting, taking up to 6 to 8 weeks to take full effect, and the overall treatment duration is typically at least 6 to 12 months or more, depending on one’s response to treatment.
- Prone to causing unwanted withdrawal symptoms when stopped suddenly
- Prescription medications: a healthcare provider decides on the treatment choice and adjusts the dose if necessary
Key Differences Between SSRIs and SNRIs
- They affect different neurotransmitters. SSRIs only target and increase serotonin levels, while SNRIs elevate both serotonin and norepinephrine levels
- Although many serotonin-related side effects overlap, the norepinephrine-related effects of SNRIs are unique
The following table summarizes the basics of SNRIs and SSRIs.
| SNRIs (serotonin-norepinephrine reuptake inhibitors) | ||
| What they target | Serotonin receptors | Serotonin and norepinephrine receptors |
| Effect | Increases serotonin between nerve cells | Increases serotonin and norepinephrine between nerve cells |
| Common uses |
|
|
| Standout |
|
|
| Key warnings |
| |
| When they start working |
| |
SNRIs vs SSRIs: An Overview
In 1987, the FDA (Federal Drug Administration) approved a new class of antidepressants called SSRIs, which promised fewer side effects and better symptom control than medications already on the market. SNRIs followed in 1993.
Initially, SSRIs and SNRIs were only registered to treat depression, but research found that:
- They both effectively managed other mental health conditions, anxiety in particular.
- SNRIs helped with some physical conditions.
Both classes prevent neurotransmitters serotonin (and norepinephrine) from entering nerve cells, increasing the levels of these feel-good chemical messengers between the brain’s nerves. This allows them to regulate one’s mood for longer.
Let’s briefly look at how exactly these neurotransmitters help balance mood. Serotonin is believed to play a key role in
SSRIs: Selective Serotonin Reuptake Inhibitors
SSRIs only block the reabsorption of serotonin, increasing its levels between the nerve cells, and making you happier and calmer. Therefore, SSRIs are commonly used to treat depression and
Possible serotonin-related side effects can include nausea, an upset stomach, sleep issues, tiredness, yawning, sexual problems, dry mouth, constipation, anxiety, weight changes, and heart rhythm issues.
Here’s a list of SSRI examples and their brand names:
- Escitalopram (Lexapro)
- Citalopram (Celexa)
- Fluoxetine (Prozac)
- Paroxetine (Paxil, Pexeva)
- Sertraline (Zoloft)
- Fluvoxamine (Luvox)
- Vilazodone (Viibryd)
SNRIs: Serotonin-Norepinephrine Reuptake Inhibitors
SNRIs target serotonin and norepinephrine receptors and increase the levels of both neurotransmitters. Not only do these medications help treat depression and anxiety symptoms, but interestingly, certain SNRIs help reduce long-standing muscle or nerve pain in conditions such as diabetes and fibromyalgia.
Because SNRIs increase serotonin, side effects overlap with those of the SSRIs, but the norepinephrine effects amplify the serotonin effects and trigger others. Some examples are high blood pressure, a rapid heart rate or palpitations, and increased irritability and seizure risk.
Here’s a list of SNRI examples and their brand names:
- Desvenlafaxine (Pristiq)
- Duloxetine (Cymbalta)
- Venlafaxine (Effexor)
- Levomilnacipran (Fetzima)
- Milnacipran (Savella)
Effectiveness: Which Is Better?
SSRI vs SNRI for Depression
SSRIs are usually considered
But these are not the only factors considered; each person’s treatment plan will be unique. For example, a patient with fibromyalgia and major depressive disorder (MDD) may benefit more from duloxetine (SNRI).
Also, people respond differently to different medications; some may have good control of depressive symptoms on a particular SSRI, while others might not, and need to try another SSRI or switch to an SNRI.
SSRI vs SNRI for Anxiety
The same decision-making and antidepressant trial process applies to choosing treatment for anxiety; there is no fixed prescribing format. Again, a healthcare provider will consider coexisting physical and mental health conditions when determining the most suitable option.
Although the preferred baseline treatment for most anxiety disorders is SSRIs, most likely because of the lower risk of side effects like irritability and anxiety spikes, both SSRIs (escitalopram and paroxetine) and SNRIs (duloxetine and venlafaxine) can be used as first-line treatments for
However, SNRIs are not registered to treat anxiety associated with OCD or PTSD.
| Condition | FDA-approved use | |
| SSRIs | SNRIs | |
| Major depressive disorder (MDD) | ✅ | ✅ |
| Generalized anxiety disorder (GAD) | ✅ | ✅ |
| Panic disorder | ✅ | ✅ |
| Social anxiety disorder (SAD) | ✅ | ✅ |
| Post-traumatic stress disorder (PTSD) | ✅ | ❌ |
| Obsessive-compulsive disorder (OCD) | ✅ | ❌ |
| Premenstrual dysphoric disorder (PMDD) | ✅ | ❌ |
| Bulimia nervosa | ✅ | ❌ |
| Chronic pain, diabetic neuropathy, and fibromyalgia | ❌ | ✅ |
| Attention-deficit hyperactivity disorder (ADHD) | ❌ | ❌ |
Switching From SSRI to SNRI or Vice Versa
At any stage, if your current medication isn’t working as well as expected or you’re not coping with the side effects, your healthcare provider may switch antidepressants from an SSRI to SNRI, or vice versa.
Your
- lowering the dose of the existing medication slowly,
- at the same time, starting the new medication at a low dose and increasing it slowly.
While it may work for medication class overlap in the case of SSRIs and SNRIs, sometimes, you might need to flush out the existing medication completely before starting the new one.
Side Effects of SSRI vs SNRI
Understanding the SNRI and SSRI side effects will help you know what to expect and when to call your medical provider for advice.
SSRIs and SNRIs share baseline side effects, the most common of which include:
- Nausea and vomiting
- Headache
- Dry mouth
- Sweating
- Dizziness
- Anxiety
- Sexual issues
- Fatigue
- Gut problems (diarrhea or constipation)
- Sleep issues (sleeping too much or insomnia)
Appetite and weight changes[12]
You might not experience them all, and for example, if you do get a headache, it might be a dull, annoying discomfort, while someone else’s could be severe enough to miss work.
Rare, but Serious Risks
There are a few other things to be aware of:
- Bleeding Risk: Platelets, the blood cells that help blood clot, require serotonin to function correctly. Because SSRIs and SNRIs block serotonin, they
increase bleeding risk[13] ; however, some studies found that it might belower in SNRIs[14] . In both classes, the risk is higher if you’re taking ibuprofen, aspirin, or other blood thinners along with an antidepressant. - Low Blood Sodium (Salt) Levels: The risk is
higher with SNRIs[15] than SSRIs. - High Blood Pressure and High Heart Rate: Because
SNRIs[16] increase norepinephrine, they can stimulate the heart to pump harder and faster;SSRIs don’t have[17] this effect. - Abnormal Heart Rhythms: The SSRIs, especially citalopram, might cause such issues; the
SNRIs appear safer[16] in this case. - Seizures: High doses of SSRIs and SNRIs can rarely cause
seizures[18] . - Suicidal Thoughts: This is more common in people under 25 years old, but it’s still important to monitor your symptoms and keep in touch with your provider.
- Withdrawal Effects: If these medications are stopped suddenly, you may experience unwanted symptoms, including:
- Rebound depression and anxiety
- Brain or body zaps
- Tiredness
- Dizziness
- Headache
- Insomnia
- Concentration problems
Below is a comparison of SSRI and SNRI side effects.
| SSRI | SNRI | |
| Nausea | ✅ | ✅ |
| Sexual dysfunction | ✅ | ✅ |
| Headache | ✅ | ✅ |
| Insomnia | ✅ | ✅✅ |
| Dry mouth | ✅ | ✅✅ |
| Sweating | ✅ | ✅✅ |
| Fatigue, drowsiness, low energy levels | ✅ | ✅ |
| Irritability and anxiety | ✅ | ✅✅ |
| Weight gain or weight loss | ✅ | ✅ |
| Bleeding risk | ✅✅ | ✅ |
| High blood pressure and heart rate | ❌ | ✅ |
| Low blood sodium levels | ✅ | ✅✅ |
| Abnormal heart rhythms | ✅ | ❌ unlikely |
| Seizures | ✅ high doses | ✅ high doses |
Safety, Special Situations, and Interactions
One special situation to mention is pregnancy. Some SSRIs and SNRIs may be used during pregnancy when benefits outweigh risks.
As mentioned above, taking antidepressants can put you at risk for rare but serious issues: high blood pressure, heart rhythm abnormalities, and suicidal ideation; and although SSRIs and SNRIs are typically safe to use with other medications, there are exceptions. This is why it’s important to tell your healthcare provider about everything you’re taking, even if it is herbal or over-the-counter.
One life-threatening reaction to be aware of is serotonin syndrome. This potentially
There are too many interactions to list for each medication in each SNRI and SSRI class, but there are some shared interactions. The more common ones are listed in the table below:*
| Possible Reaction with SSRIs and SNRIs | Medication |
| Serotonin Syndrome |
|
| Decreased effectiveness in controlling pain | Opioids: Codeine, hydrocodone |
| Reduced effectiveness | Tamoxifen |
| Increased risk of seizures |
|
| Increased risk of bleeding |
|
*For information about all the possible different interactions, consult with your healthcare provider or pharmacist.
Lastly, what about combining SSRIs and SNRIs? Can they be taken together? The answer is generally not, and only ever under specialist guidance, as the risk of side effects and serotonin syndrome could increase.
Choosing Between SSRIs and SNRIs
A healthcare provider can prescribe an antidepressant after going through the
- Your mental health condition, the diagnosis
- Coexisting medical conditions
- Other medications you’re taking
- What you prefer (after
discussing[22] all the options)
Because everyone is different, there are no guarantees about the effectiveness and side effects of an SSRI versus SNRI, and your medical provider will monitor you closely to ensure you’re on the correct medication.
Also, note that not everyone needs medication. Based on the results of a health evaluation, you may be offered non-medication treatment options if they are more appropriate. It is also proven effective to combine pharmacological treatment of depression and anxiety with psychotherapy.
Final Thoughts: SSRI vs SNRI
While SSRIs and SNRIs share similarities, particularly in the conditions they treat and common side effects, they differ in several respects. And although you now have an overview of these antidepressants, you should get advice from a qualified healthcare professional on what options are appropriate for you.
MEDvidi’s medical team offers online help for depression and anxiety, ongoing support, and online medication management if necessary. Book your virtual appointment now to get assessed and receive your individualized treatment plan.
FAQs
Which is better: SSRIs or SNRIs?
It is not possible to say whether an SSRI or SNRI is better than the other, as there are many factors to consider. The doctor’s recommended medication depends on symptoms, diagnosis, current medications, and coexisting physical and mental health conditions. Even then, individuals will respond differently to each medication.
Can you take SSRIs and SNRIs together for faster results?
SSRIs and SNRIs are relatively safe medications; however, there is no evidence that taking them together yields faster results. Instead, it may increase the risk of side effects, and such combinations are generally not recommended.
Is it possible to switch from SNRIs to SSRIs?
Yes, it is possible to switch from SNRIs to SSRIs, but only if recommended and supervised by a healthcare professional.
Which is the safer medication: SSRI or SNRI?
An SSRI or SNRI will be the safer option in different situations. The safer choice depends on many factors, a few examples are your mental health diagnosis and medical history.
Is it safe to use SSRIs or SNRIs during pregnancy?
Some SSRIs and SNRIs may be used during pregnancy when benefits outweigh risks. Paroxetine has been associated with a higher risk of fetal cardiac defects and is used with caution. Treatment decisions should be individualized in consultation with a healthcare provider.
How to get an SSRI or SNRI prescribed?
To get an SSRI or SNRI prescribed, you should first consult a medical provider, either in person or online. If they diagnose you with a condition that the antidepressant class is registered to treat, such as anxiety or depression, and an SSRI or SNRI is appropriate in your situation, they may prescribe it to you.
Do SNRIs or SSRIs cause weight gain?
Weight gain is a common
Are SNRIs harder to get off than SSRIs?
In general, SNRIs are harder to get off than SSRIs, but it also
