SNRIs: What Are They, Uses, Side Effects & More

One in every 15 American adults suffer from depression in any given year. And more than 18 percent of people in the United States suffer from anxiety disorders each year.

So if you’re suffering from one or both of these conditions, you’re not alone—and you don’t have to continue to suffer, either.

Antidepressants work for many patients with depression or anxiety disorders, and they’re commonly prescribed to relieve both: Nearly 13 percent of American adults have taken at least one dose of these medications in the last 30 days.

Most antidepressants work by affecting chemicals in the brain called neurotransmitters, including serotonin, norepinephrine, and dopamine.

There are five main classes of antidepressants, each affecting these neurotransmitters in different ways. One of these classes of medications are serotonin and norepinephrine reuptake inhibitors, or SNRIs.

In this article, I’ll describe what SNRIs are, how they work, and the side effects that they can cause. I’ll also cover the most common SNRI medications, their safety and risks, and how they interact with alcohol and other drugs.

Finally, I’ll explain when you may consider switching from SSRIs to SNRIs and when to consult with your healthcare provider if a medication is not working well for you.

What Are SNRIs?

Serotonin and norepinephrine reuptake inhibitors, or SNRIs, are a type of antidepressant prescription medication that are commonly used for depression and anxiety disorders, as well as some other mental health conditions. 

What Do SNRIs Treat?

SNRIs can be prescribed to treat depression including major depressive disorder (MDD), anxiety disorders including generalized anxiety disorder (GAD), and long-term chronic pain, including nerve pain. 

How Do SNRIs Work?

Most antidepressants work by affecting chemicals in the brain called neurotransmitters, including serotonin, norepinephrine, and dopamine. 

SNRIs work on two of these neurotransmitters, serotonin and norepinephrine, which are chemicals that can help regulate mood.

SNRIs increase the levels of these chemicals in your brain and body by blocking the reabsorption (or reuptake) of used serotonin and norepinephrine molecules in the brain. Because they affect two brain chemicals, SNRIs are sometimes referred to as dual reuptake inhibitors or dual-acting antidepressants.

SNRIs vs SSRIs

Selective serotonin reuptake inhibitors, or SSRIs, are often the first-line treatment prescribed by doctors for depression and anxiety.

SSRI medications generally cause fewer adverse effects and are less likely to cause problems at higher doses than SNRIs or other families of antidepressants.

As suggested by their name, SSRIs work by blocking the reuptake of of the chemical serotonin in the brain, thus increasing the amount present in the brain. Examples of SSRI medications include sertraline (Zoloft), fluoxetine (Prozac), paroxetine (Paxil), fluvoxamine (Luvox), citalopram (Celexa), and escitalopram (Lexapro). 

Both SNRIs and SSRIs work to increase levels of serotonin in the brain, which can help with the symptoms of anxiety, depression, and other mental health conditions.

SNRIs also affect a second chemical, norepinephrine. Norepinephrine can play an important role in sleep, attention, memory, and mood regulation, and as a result, can be particularly effective at helping people concentrate.

While they are not specifically ADD or ADHD treatments, some SNRIs, like venlafaxine (Effexor XR), may help decrease symptoms of attention deficit hyperactivity disorder (ADHD).

Increasing norepinephrine activity may have a negative impact on people who have panic disorders, hyperactive behavior, or high blood pressure, so it’s important to work with your healthcare provider to determine the best fit for you.

There is no one type of antidepressant that is more effective than others. It simply depends on the individual: Some patients will respond better to one type of medication than another.

Your healthcare provider can work with you to find the best option for your personal needs and symptoms.

Do SNRIs Work for Anxiety?

Yes. Several SNRIs can be prescribed in the treatment of anxiety disorders. Duloxetine (Cymbalta) and venlafaxine (Effexor XR) are both commonly used to treat anxiety.

SNRI Side Effects

Not all patients will experience side effects on an SNRI. Mild side effects that occur within the first two weeks will often improve after a few weeks.

In some cases, you may experience side effects the entire time you are on the medication.

The most common side effects of SNRIs are:

• Nausea
• Dry mouth
• Dizziness
• Headache
• Excessive sweating
• Tiredness or fatigue
• Constipation
• Insomnia
• Sexual dysfunction (including low libido, difficulty reaching orgasm, or erectile dysfunction)
• Loss of appetite
• Increased blood pressure

Each type of SNRI has a different chemical makeup and the effects vary from person to person. If you have trouble tolerating one SNRI, another might be better for you. In some cases, a different family of antidepressant may be a better fit for you.

Speak to your healthcare provider about problematic side effects you experience.

Do SNRIs Cause Weight Gain?

SNRIs may cause weight gain for some users, while other patients may experience weight loss. Many individuals do not see any weight change at all.

Overall, SNRIs tend to be more neutral for weight than some other types of antidepressants. 

Experts aren’t certain why some antidepressants affect weight. Some believe that the medication’s impact on neurotransmitters in the brain have an impact on metabolism.

Others believe that weight gain or weight loss is an indirect side effect of the medications caused by changes in appetite or behavior related to your mood.

For example, some people use food and overeating to cope with the stresses of anxiety and depression. In this case, when they start antidepressant medication, they no longer feel the need to eat emotionally, which can lead to weight loss.

The opposite reaction is possible, too. For people who lose their appetite as a result of their depression, getting effective treatment may help their appetite return, causing a modest weight gain. 

What Are the SNRI Medications?

The Food and Drug Administration (FDA) has approved the following SNRIs for public use:

• Desvenlafaxine (Pristiq)
• Duloxetine (Cymbalta)
• Levomilnacipran (Fetzima)
• Milnacipran (Savella), also used to treat fibromyalgia
• Venlafaxine (Effexor XR)

SNRIs and Alcohol

SNRI use is a possible risk factor for a potentially fatal syndrome called rhabdomyolysis (RML) if alcohol is consumed.

When a person has “rhabdo,” damaged muscle tissue releases proteins into the blood, which can result in permanent disability, and even death.

People on SNRIs should avoid alcohol as much as possible to avoid this risk. In addition, taking Cymbalta with alcohol can increase your risk of liver problems.

Switching from SSRIs to SNRIs

In many cases, SNRIs work very well for anxiety without significant side effects. However, if you don’t react well to a specific kind of SNRI, ask your provider about adjusting the dose or switching to another family of medications.

Discuss the pros and cons with your provider before making such a decision.

Safety

When used as directed, SNRIs can be an effective and safe treatment option for depression, anxiety, or nerve pain.

SNRIs may not be right for everyone, though. Talk with your doctor if you’re pregnant or plan to become pregnant, are breastfeeding, and if you have a history of panic attacks or high blood pressure.

Additionally, any antidepressant use in people under 25 may cause an increase in suicidal thoughts or behavior, especially in the first few weeks after starting the medication or when the dose is changed.

If you’re starting an antidepressant regimen and any of these feelings arise, reach out to your healthcare provider, call 9-1-1 or 988, or go to the emergency room.

Drug Interactions

SNRIs may increase your risk of bleeding if you take other medications that can increase the risk, including ibuprofen, aspirin, warfarin, and other blood thinners.

Before starting this or any other medication, let your prescriber know of all the prescription and over-the-counter (OTC) medication you’re taking to avoid any adverse drug interactions.

Stopping SNRI and Withdrawal

For some people, it can take time to find the medication that’s right for you. Deciding whether to stop taking your SNRI should be considered thoughtfully with the support of your healthcare provider.

If you decide to stop taking the medication, talk with your provider about the steps you can take to minimize or avoid symptoms that can occur when you stop taking the medication.

When you stop SNRI use abruptly, withdrawal symptoms can occur. These symptoms may be more likely to occur when discontinuing venlafaxine or desvenlafaxine. Symptoms can include:

• Dizziness
• Headache
• Flu-like symptoms (including tiredness, chills, and muscle aches)
• Sleep changes (including insomnia and nightmares)
• Diarrhea
• Nausea
• Irritability or agitation

Tapering your dosage slowly with the help of your healthcare provider can help minimize or completely eliminate these symptoms.

Follow your provider’s medical advice on the recommended approach if you decide to stop taking your medication.

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