SSRI and SNRI (antidepressants)
Antidepressants come in two basic types: selective serotonin reuptake inhibitors (SSRIs) and serotonin and norepinephrine reuptake inhibitors (SNRIs). While SNRIs raise serotonin levels as well as norepinephrine, SSRIs only raise serotonin levels.
Learn about Types of Depression
Why are serotonin and norepinephrine important?
Neurotransmitters are chemicals in your brain that aid in the transmission of nerve signals between neurons, and both SSRIs and SNRIs act on them.
Serotonin
Your body uses the neurotransmitter, serotonin, to control your mood. You may become depressed if your serotonin levels are too high or too low.
Low serotonin levels can also lead to anxiety, depressive thoughts, suicidal thoughts, or compulsive behaviors. If your serotonin levels are too high, you may feel less physically and mentally active and/or excited, causing you to feel more relaxed and sleepy.
Norepinephrine
A crucial component of your “fight-or-flight” response is another neurotransmitter called norepinephrine. Norepinephrine naturally increases during periods of high stress, such as when you feel threatened.
Norepinephrine is also involved in controlling your mood, sleep, attention, and memory. Low norepinephrine levels can make it difficult to focus, cause attention deficit hyperactivity disorder (ADHD) symptoms, or cause depressive symptoms in certain people.
Euphoria may be caused by norepinephrine levels that are too high. However, they can also result in hyperactivity, increased blood pressure, and panic attacks.
SSRI vs SNRI
| Prozac (Fluoxetine) | Zoloft (Sertraline) |
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| Differences | |
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There is insufficient evidence that one drug class or the other is consistently better for everyone.
Learn about The first few weeks on antidepressants
SSRI medications
- Citalopram (brand: Celexa) 20–40 mg daily
- Escitalopram (Lexapro) 10 mg daily
- Fluoxetine (Prozac, Sarafem) 10–60 mg daily, or 90 mg weekly
Sarafem 20 mg daily may be used for premenstrual dysmorphic disorder (PMDD) - Paroxetine (Paxil, Paxil CR, Pexeva, Brisdelle) 10-60 mg daily
- Sertraline (Zoloft) 50–200 mg daily
May be used for premenstrual dysmorphic disorder (PMDD) - Fluvoxamine IR/ER 50–300 mg daily
This medication is only approved for the treatment of OCD
Common side effects of SSRIs
- Sexual dysfunctions (i.e. decreased sexual desire, ejaculation difficulties, erectile dysfunction)
- Sleepiness
- Insomnia
- Nausea
- Dry mouth
- Weakness
- Tremor
- Dizziness
- Headaches
But SSRIs may help for migraines if taken continuously
SNRI medications
- Venlafaxine (Effexor XR) 37.5–375 mg daily
Approved for the treatment of depression, generalized anxiety disorder, panic disorder, and social anxiety disorder - Duloxetine (Cymbalta) 40–60 mg daily, or 20-30 mg BID (twice a day)
Approved for the treatment of depression, peripheral neuropathy (pain), fibromyalgia, generalized anxiety disorder, chronic musculoskeletal pain - Desvenlafaxine (Pristiq, Khedezla) 50 mg daily
Approved for the treatment of depression - Levomilnacipran (Fetzima) 40–120 mg daily
Approved for the treatment of depression
Common side effects of SNRIs
- Increase heart rate
- Dilated pupils
This can lead to an episode of narrow open-angle glaucoma - Dry mouth
- Excessive sweating
- Constipation
- Dizziness
- Nausea
- Headaches
Speak With Your Doctor
Both SSRIs and SNRIs have been shown to significantly reduce symptom severity in many individuals with depression, anxiety, and various medical conditions.
Learn more about how SSRIs and SNRIs are used to treat depression and general anxiety disorder.
To get started on your treatment plan, talk to your healthcare provider about choosing between SSRI or an SNRI, and send your prescription to Marley Drug. Save up to 95% compared to your local pharmacy by using Marley Drug.