What side effects are common when switching from an SSRI to an SNRI? 

In this blog post, we are going to answer the question, “What side effects are common when switching from an SSRI to an SNRI?”. SSRIs are selective serotonin reuptake inhibitors. They are one of the most commonly prescribed antidepressants in the entire world. 

However, they still may not work well for every single individual. Some people get allergic to them and some can’t tolerate the side effects that are associated with these antidepressants. 

This blog will discuss what happens when your doctor switches you from SSRIs to SNRIs, short for serotonin-norepinephrine reuptake inhibitors. 

What side effects are common when switching from an SSRI to an SNRI? 

The common side effects associated with switching your antidepressant from an SSRI to SNRI include:

  • SSRI withdrawal syndrome 
  • Psychological side effects 
  • Risk of serotonin syndrome 
  • Gastrointestinal complications 
  • An allergic response to SNRI

SSRI withdrawal syndrome 

SSRI withdrawal syndrome is one of the biggest concerns when your antidepressant is switched. This is because your body is used to getting an SSRI, whichever one you are taking. 

These meds help to increase the amount of active serotonin in your body and that works to counteract the symptoms associated with depression, anxiety, and other mental health conditions. When you start to take these meds, the first few weeks are the toughest. 

During this time period, your body is not adjusted to the antidepressant. It takes your pill as a foreign object. Once your body is completely adjusted to this med, it eventually starts depending on it for the normal activity of serotonin, which is an excitatory monoamine neurotransmitter. 

Now, if you take away the SSRI quickly, you will be subjected to withdrawal symptoms, even if you readily replace it with an SNRI. This is why you should always go through this process as slowly as possible. 

Antidepressants are not that easy to deal with and every single precaution should be taken to ensure safe and effective use, as well as safe withdrawal when needed. 

Psychological side effects 

When you switch from an SSRI to an SNRI, your body gets a little confused. This is because you have been taking an SSRI for a long time and your body is familiar with it, but it is not familiar with the SNRI. It is a known fact that antidepressants take 4 to 6 weeks to start working. 

The same will happen when you switch it. It does not matter if you’re switching from one antidepressant to another because your body will start the entire process from the start.

When you take an SNRI, your body takes some time to adjust to it. Meanwhile, your psychological health may get a little disturbed. During the switching process, you may suffer from the following symptoms:

  • Anxiety 
  • Irritability 
  • Restlessness 
  • Insomnia or inability to fall asleep 
  • Drowsiness 
  • Dizziness 
  • Rapid mood changes
  • Confusion 
  • Forgetfulness 
  • Intrusive thoughts 
  • Worsen Depression 
  • Sadness
  • Hopelessness 
  • The feeling of isolating yourself 
  • Inability to perform well in social gatherings 

These side effects can vary from person to person. Some people may not feel much, but the switching process can significantly damage their mental health. 

Psychological side effects are usually at their peak when you have completely stopped the SSRI and you’re in your early days with the new SNRI. At this time period, your mind is confused. 

The med was dependent on has now stopped, whereas it is not yet familiar with the antidepressant you’re taking currently. This is why you should always consult your healthcare provider for such matters. 

Your doctor will determine the best possible switching strategy for you to save you from such psychological side effects. Make sure you strictly follow your SSRI taper schedule. If you stop too quickly, you will damage your mind more than you can imagine. 

What side effects are common when switching from an SSRI to an SNRI? 

Risk of serotonin syndrome

Another important concern is the risk of serotonin syndrome. This is a common concern when you’re tapering off your SSRI while starting SNRI at the same time from the lowest effective dose. This strategy is common when switching from SSRIs to SNRIs. 

However, one wrong dose administration can lead to disturbing symptoms associated with serotonin syndrome. This happens when people take more of each antidepressant than the prescribed dose. 

During this type of switching strategy, you take both of the antidepressants together. The doses are kept low to save you from any complications, but non-adherence can get in the way. Some people may willingly or accidentally take more than they should. 

This can result in too much serotonergic activity in your brain, which is the root cause of serotonin syndrome. This condition can take a drastic turn pretty quickly and can lead to life-threatening complications. This is why you should stick to your doctor’s recommended dose. 

When you’re in the middle of your antidepressant switching strategy, you should take your meds as properly as you can. If you suffer from forgetfulness, try to make a checklist and mark it as soon as you take your antidepressants. 

You can set a reminder on your phone to take your antidepressant so you won’t miss a dose. Once the dose is taken, you can mark it done or turn off your reminder alarm. Just look for the best possible way to remember to take your meds so that you won’t miss them and you won’t accidentally take them twice. 

Gastrointestinal complications 

Gastrointestinal side effects are common when you switch from an SSRI to an SNRI. This is because both of these classes of antidepressants are associated with gastrointestinal side effects with variable intensities. 

You’re probably aware of the fact that antidepressants produce side effects way before they start to treat your depression. As we have already discussed, antidepressants take time to work. 

Some can even take as long as 8 weeks to just kick in. During this time period, these meds produce a number of side effects. When you continue with the treatment, despite the side effects, your body slowly becomes adjusted and these side effects slowly begin to subside. 

When you switch your antidepressant, this process starts again. Yes, you must think that just the drug is changed, the effects are expected to be the same as they both are antidepressants, but that’s now how your body sees it. 

Imagine you’re replacing your assistant at work after several months. Although the new assistant will have the exact same job description, you will still take some time to get to know them. It’s not just about the work, but also how you bond with your new assistant. 

Similarly, your body bonds with medications too. When you switch from an SSRI to an SNRI, your body gets introduced to a new drug and the entire cycle repeats again. You may suffer from the following gastrointestinal side effects:

  • Nausea 
  • Vomiting 
  • Diarrhoea or Constipation 
  • Upset stomach 
  • Flatulence and bloating 
  • Acid reflux or heartburn 
  • Abdominal pain 
  • Inability to digest food properly 
  • Stomach pain after every meal

These side effects can vary from person to person and they usually begin to subside within 2 to 3 weeks. However, if you experience any unusual gastrointestinal side effects, immediately reach out to your healthcare provider. 

An allergic response to SNRI

The biggest concern when it comes to switching your antidepressant from SSRIs to SNRIs is how your body will respond to it initially. There are some people who are naturally allergic to some medications, more particularly to some active chemicals which are responsible for producing a therapeutic response. 

The funny thing is that there’s no way to tell which chemical you are allergic to unless you actually take it. Several studies have suggested that some people can be naturally allergic to SNRIs or some particular SNRI. 

For such people, the treatment does not last very long because they simply can not tolerate the presence of this antidepressant in their bodies. If you exhibit any sign of an allergic reaction soon after taking your first ever SNRI dose, immediately report to your healthcare provider. Some of the common symptoms include:

  • Redness of skin
  • Itching
  • Rash or hives
  • Burning sensation
  • Painful blisters
  • Blue-purple patches
  • Tightness of chest
  • Wheezing
  • Difficulty in breathing 
  • Hoarseness 
  • Swelling of eyes, lips, tongue, throat, etc. 

These symptoms can vary from person to person. People who get severely allergic to SNRIs can develop unbearable throat swelling and it even becomes difficult for them to breathe. These reasons lead to the discontinuation of treatment.


In this blog post, we have discussed the side effects that commonly occur when you switch from an SSRI to an SNRI. These side effects can vary from person to person and may affect some people more than others. 

This is why you should always stick to your doctor’s recommendations. You should never switch your antidepressant without your doctor’s supervision. There are a lot of risks that can damage your health if you don’t follow your doctor’s directions. 

FAQs: switching from SSRI to SNRI side effects 

Can you switch directly from SSRI to SNRI?

Yes, you can directly switch from an SSRI to an SNRI, but only if your healthcare provider recommends this. In usual practice, your doctor will gradually taper off your SSRI dose. Meanwhile, a very low dose of SNRI is started to kind of introduce the drug to the brain. As the process goes on, SSRI is slowly tapered off and then stopped finally, whereas the dose of SNRI is gradually increased until it reaches the most appropriate dose as per your condition. 

Does SNRI have more side effects than SSRIs?

SNRIs may cause more side effects than SSRIs in some people. However, SSRIs are also associated with side effects and there are people who are being treated with SNRIs simply because they could not bear SSRIs. This totally depends on how your body responds to the meds and how severe your mental health condition is. 

If we look at the mechanism of action, research indicates that SNRIs can cause more side effects because they increase the levels of two excitatory monoamine neurotransmitters; serotonin and norepinephrine. SSRIs, on the other hand, only increase the amount of serotonin. They do not inhibit the reuptake of norepinephrine in any way. 

How long does it take to adjust to SNRI?

It usually takes 4 to 6 weeks to adjust to an SNRI. This is because these meds do not have a rapid onset of action and they can not treat your depression overnight. You need to give your body some time to completely adjust to these meds first. During this time, you may suffer from some side effects, but they usually start to fade away once your body adjusts to the medication. 

Do SNRIs make you feel worse before better?

Yes, SNRIs and other antidepressants may make you feel worse before they make you feel better. This is because these meds do not start to work overnight. They need at least 4 to 6 weeks to start working. Before that, they show no therapeutic outcome, but they do cause side effects. This is why you feel worse before actually feeling better. However, you should stick to your doctor’s recommended dose and wait for your antidepressant to work. 

What to expect when switching antidepressants?

When you’re switching from one antidepressant to another, you have to remember that it’s not a magical process. Your new antidepressant won’t start working overnight or treat your symptoms in a blink of an eye. The new drug will take its time to kick in and your body will take its time to adjust to this new antidepressant. You may also suffer from some side effects. However, they will begin to subside soon after your body adapts to the new antidepressant.