SNRIs (selective serotonin-norepinephrine reuptake inhibitors) and SSRIs (selective serotonin reuptake inhibitors) are the two most widely used classes of antidepressants prescribed for various mental health problems. They belong to the new group of antidepressants that are safer and have fewer side effects than the old ones, and bring noticeable improvement in mental health.
Despite their numerous similarities, some vital differences exist in their working pattern, potential uses, side effects, and drug interactions. This article will answer all your lingering questions about these drugs and help you have a more detailed discussion with your doctor about which antidepressant class might be more suitable for you, SNRI or SSRI.
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SNRI Vs. SSRI: Overview
FDA approved SSRIs in 1987, whereas SNRIs were introduced into the market in 1993 to usher in the new era of antidepressant medications. Initially, these drugs were developed to treat depression, but with continued research, it has been found that they effectively manage various other psychological and physical conditions. The list of drugs belonging to each class is given:
|Escitalopram (Lexapro)||Desvenlafaxine (Pristiq)|
|Citalopram (Celexa)||Duloxetine (Cymbalta)|
|Fluoxetine (Prozac)||Venlafaxine (Effexor)|
|Paroxetine (Paxil, Pexeva)||Levomilnacipran (Fetzima)|
|Sertraline (Zoloft)||Milnacipran (Savella)|
Overall, these new antidepressants have better tolerability, safety profile and less dosing issues. They help improve the quality of life in the long run by lowering and diminishing the symptoms of various psychological problems, including depression, anxiety disorders, phobias, OCD, PTSD, etc.
SNRI Vs. SSRI: Differences and Similarities
The key difference between SNRI and SSRI lies in their mechanism of action. SSRIs work by delaying serotonin uptake in the brain by nerve cells. As a result, more serotonin is available for a longer duration in the brain, which lessens depressive symptoms in patients.
SNRIs also follow the same principle of working with one crucial alteration. In addition to blocking serotonin uptake, they also block the reuptake of norepinephrine in the brain.
Here it is important to mention the role of serotonin in balancing mood. Serotonin is one of the neurochemicals that plays a key biological role in happiness. Whenever we are involved in pleasurable activities, our brain releases certain “happy hormones and chemicals”, including dopamine and serotonin. In depression, it is hypothesized that there is a lack of serotonin in the brain and antidepressants (SSRIs and SNRIs) work to balance these “happy hormones” in the brain.
In contrast, norepinephrine is vital in the body’s reaction to any emergency — fight or flight response. Whenever a person experiences intense stress for any reason, e.g., an exam, job interview, etc., the levels of norepinephrine increase in the body. It also impacts a person’s sleep, reasoning, motivation, and mood. Hence, it is hypothesized that its imbalance in the body can also result in depression.
Apart from these differences in their functioning, there are also many similarities between SSRIs and SNRIs, including their safety, efficacy, and duration of treatment. The following table summarizes the important aspects of SNRIs and SSRIs:
|Feature||SSRIs (Selective serotonin reuptake inhibitors)||SNRIs (Selective serotonin-norepinephrine reuptake inhibitors)|
|Mechanism of Action||Targets serotonin receptors||Targets serotonin and norepinephrine receptors|
|Half-life||Relatively long as compared to other antidepressants||Relatively short as compared to other antidepressants|
|Safety||Relatively safe as compared to older antidepressants|
|Efficacy||Comparable to older antidepressants|
|Duration of Treatment||Long (usually 6 months or more depending on the patient’s condition)|
|Dosage||Depends on the specific drug and the condition treated|
|Cost||Variable and depends on the specific drug|
|Insurance Coverage||Depends on the insurance provider|
|Online prescription||Available at MEDvidi|
Ask a mental health professional which medication will help you overcome your tedious symptoms.
SNRI Vs. SSRI: Uses
SNRIs and SSRIs are widely used for various mental health conditions and some physical problems. Each drug in these antidepressant classes is prescribed for different label and off-label treatments.
Let’s have a breakdown of different conditions treated by SSRIs and SNRIs.
All the SSRIs are recommended by the FDA to treat depression except fluvoxamine (Luvox), which is used for OCD treatment. Certain SSRIs (sertraline and fluoxetine) decrease the symptoms of depression (PMDD), associated with women’s menstrual cycle.
Currently, four SNRI drugs have the approval for depression treatment; the drug missing out is milnacipran (Savella) which is approved for treating fibromyalgia in the US. These drugs are usually prescribed for moderate to severe depression because they are not as effective in the case of mild depression.
Both SNRIs and SSRIs are approved by the FDA to treat panic disorders associated with or without agoraphobia. Three drugs in the family of SSRIs — paroxetine, fluoxetine, and sertraline — are prescribed to manage panic disorders. These agents are especially helpful in cases of comorbid depression with panic disorder.
MEDvidi doctors are certified to prescribe SNRIs and SSRIs and will find the meds that will suit your treatment goals best.
Fluvoxamine (Luvox), which is an SSRI, is specifically licensed to manage OCD in people. Along with fluvoxamine, other SSRIs, including paroxetine, sertraline, and fluoxetine, are also used for OCD treatment. The doses to treat OCD are typically higher than depression doses, and it takes a long time before their beneficial effects become evident in OCD patients. In comparison, no SNRI has been approved by the FDA for OCD treatment. However, they are prescribed off-label for this condition.
Generalized and Social Anxiety Disorder
Some SSRIs and SNRIs are used to treat generalized and social anxiety disorders and specific phobias. The choice of drug depends on the diagnosis and symptoms intensity of a specific condition. FDA has approved paroxetine, escitalopram, duloxetine, and venlafaxine for generalized anxiety disorder (GAD), whereas sertraline, paroxetine, and extended-release venlafaxine are the drugs of choice for social anxiety.
Posttraumatic Stress Disorder
Therapy is the first-choice treatment for PTSD. However, medications may also be required for quick symptom relief. For this purpose, doctors mostly recommend SSRIs, as they are effective in controlling intrusive and avoidant symptoms associated with PTSD.
Bulimia and anorexia are compulsive disorders related to eating habits and are also treated with SSRIs. In particular, fluoxetine is used for this purpose. Although psychotherapy is the treatment of choice for these disorders, adding SSRI to the management plan can help reduce binge eating and vomiting associated with bulimia.
Neuropathic Nerve Pain
In addition to mental health problems, these drugs are also prescribed to manage some physical conditions. SNRIs are prescribed for controlling different nerve pains in the body. The FDA has approved Duloxetine to treat neuropathic pain associated with diabetes and fibromyalgia (chronic muscular pain).
Off-label use means when a doctor prescribes an approved drug for a medical condition not yet approved by FDA to treat that condition. The SSRIs and SNRIs are used off-label for the following medical ailments.
SSRIs are prescribed off-label to treat premature ejaculation in men due to their anorgasmic effects. Usually, fluoxetine and sertraline are used for this purpose.
Long-standing migraine headaches are also sometimes treated with SSRIs, especially in patients with associated depression.
Some SSRIs are prescribed to manage the symptoms associated with the autism spectrum disorder.
Stress Urinary Incontinence
Duloxetine is currently under review by the FDA for approval to treat the most common type of urinary incontinence (inability to hold urine) in women — stress incontinence.
Major depressive disorder
Obsessive-Compulsive Disorder (OCD)
Generalized Anxiety Disorders (GAD)
Social anxiety disorder (SAD)
Premenstrual dysphoric disorder (PMDD)
Post-traumatic stress disorder (PTSD)
Anxiety disorders do not go by themselves. Seek professional help to feel calm and productive again.
SNRI Vs. SSRI: Side Effects and Interactions
SSRIs and SNRIs mostly cause the same side effects that, in turn, vary from person to person. If someone is experiencing a particular side effect from these drugs, it doesn’t mean that other people will also face a similar intensity effect.
The most common side effects of SSRIs and SNRIs include:
- Blurred vision
- Dry mouth
- Sexual dysfunction
- Problems with the gut (diarrhea or constipation)
- Problems with sleep
- Nausea and vomiting
- Weight changes (increase or decrease)
The more serious side effects of these medications are disclosed below in detail.
Effects on the Heart
SSRIs and SNRIs can cause prolongation of QT intervals in the heart, leading to rhythm abnormalities in the heart. The risk is especially high in people who are also taking antipsychotic medications in addition to antidepressants. Of all the drugs, citalopram affects the QT interval the most.
Some mental conditions have similar symptoms. Take a free online assessment and consult with a doctor to get a diagnosis and start proper treatment.
SSRIs and SNRIs can cause increased incidences of headaches in patients, according to a study.
Higher doses of SSRIs and SNRIs can cause seizures in patients, although it is a rare side effect.
Effects on Blood
SSRIs and SNRIs cause certain blood-related problems like impairment of platelet aggregation. It can expose patients to excessive bleeding risk in case of trauma. Hence, these drugs are used with extra caution when taken alongside NSAIDs like ibuprofen or blood thinners, such as aspirin.
Effects on Blood Sugar and Electrolytes
These antidepressants can lower blood sugar levels in patients with diabetes. Therefore, these drugs must be used cautiously in patients with blood sugar problems. Also, they can affect the levels of certain electrolytes, especially sodium, in the body, causing tiredness.
Effects on Hormones
The SSRIs can increase prolactin hormone levels, primarily associated with breast enlargement and milk production, in both women and men. The breast changes that might occur while on these drugs are reversible after discontinuation of the treatment; however, it can take a long time for the changes to reverse.
SSRIs can cause movement problems in patients like akathisia (inability to remain still), torticollis (neck twisting), dystonia (involuntary movements), bradykinesia (slow movements), and opisthotonos (muscle spasms).
If SSRIs or SNRIs are taken with other antidepressants like monoamine oxidase inhibitors (MAOIs), lithium, or l-tryptophan, they can increase serotonin in the body to dangerously high levels causing a myriad of symptoms known as serotonin syndrome. The main characteristics of this disorder are:
- Extreme nervousness
- Involuntary body movements
- High temperature
- Cardiovascular collapse
Consult with a doctor if you have any side effects. MEDvidi professionals are there to help tailor your plan and adjust the dosage of the medications you take.
Acute Withdrawal Effects
If these drugs are stopped abruptly, there is a potential for withdrawal effects. The symptoms of sudden discontinuation of these drugs may include:
- Rebound depression
- Concentration problems
*Black Box Warning. FDA has put some SSRIs and SNRIs (fluvoxamine, paroxetine, fluoxetine, sertraline, citalopram, and venlafaxine) on the list of drugs that carry some serious side effects. In the case of SSRIs and SNRIs, this warning is due to their risk of causing suicidal thoughts in children, adolescents, and young adults up to the age of 24. Therefore, these age groups are monitored very closely during the early phase of the treatment if they are prescribed any of these drugs.
The table below lists the common and serious side effects associated with SSRIs and SNRIs.
Common side effects of SSRIs and SNRIs
Serious side effects of SSRIs and SNRIs
Tell a prescriber about all the medications you take when getting antidepressants. A thorough overview allows the doctor to help you avoid dangerous meds interactions.
Interactions with Other Drugs
SSRIs and SNRIs are typically safe to use with other drugs. Still, there are some interactions that you should be aware of and report taking any of these drugs to your doctor before commencing antidepressant treatment.
The drug interactions of SNRIs and SSRIs are similar, and the most common ones are given in the table below:
|Drug||Drug Class||Possible Reaction with SSRIs and SNRIs|
|Lithium||Antimanic agents||Serotonin Syndrome|
|L-Tryptophan||α-amino acid||Serotonin Syndrome|
|TCAs||TCA clinical toxicity|
|Opioids||Decreased effectiveness in controlling pain|
|Tamoxifen||Non-steroidal antiestrogen||Reduced effectiveness|
|NSAIDs||Increased risk of gastric bleeding|
|Clozapine||Atypical antipsychotics||Increased risk of seizures|
|Anticoagulants||Increased risk of bleeding|
*For information about all the possible different interactions, consult with a doctor or pharmacist.
Enough data is not available yet to determine the changes caused by these drugs in lab test results.
SNRI Vs. SSRI: FAQs
Many studies have been concluded to compare the efficacy of SSRI and SNRI; however, no clinical advantage has been found in favor of one drug class over the other. The SNRIs have a slight advantage in the mechanism of action as they target serotonin and noradrenaline receptors in the brain as compared to SSRIs that only target serotonin receptors. However, the ultimate choice of drug will depend on the patient’s symptoms, diagnosis, and the doctor’s decision based on the overall assessment.
SSRIs and SNRIs are relatively safe drugs; however, no evidence suggests combining these can help bring faster results. Additionally, it is highly advisable to follow only your doctor’s instructions while using these drugs to avoid any serious complications.
Yes, it is possible to switch from SNRIs to SSRIs. But before making such a change in your treatment plan, your doctor has to consider many things: medical and drug history, response to treatment, side effects, etc. Only after proper evaluation and ruling out the red flags a doctor can switch your medication from SNRIs to SSRIs.
SSRIs and SNRIs share more or less common side effects. No medical evidence suggests that one of them is safer than the other. The choice of drug for the treatment depends on your medical condition, medical history, and other factors like age and genetics.
Most SSRIs and SNRIs are safe to use during pregnancy. But paroxetine (SSRI) can increase the risk of congenital defects, especially heart abnormalities; therefore, it should be avoided during pregnancy.
To get a prescription for SSRIs or SNRIs, you have to get yourself assessed by a doctor to determine your need for any of these drugs. Nowadays, telemedicine has made this process much easier. You can get a prescription from the comfort of your home — a simple and cost-effective process without requiring you to visit a doctor’s office.
The above information concludes that SSRIs and SNRIs are more or less similar in their uses, tolerability, efficacy, and safety profile, with only a few minor differences. With that being said, only a qualified physician can figure out which drug is best for your condition after thoroughly evaluating your medical information. At MEDvidi, we have an experienced medical team that is 24/7 available to answer all your queries regarding antidepressant medications. Book your online appointment now and speak to one of our doctors if you are experiencing signs and symptoms of depression or other related mental health conditions.
To get an online consultation with a licensed prescriber, contact MEDvidi. Our mental health experts offer treatment for various mental health issues such as general anxiety disorder, depression, stress, ADHD, and other mental health problems.