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Serotonin and norepinephrine reuptake inhibitors (SNRIs)
Antidepressant SNRIs help relieve depression symptoms, such as irritability and sadness. Here's how these antidepressants work and what side effects they may cause.
By Mayo Clinic staffSNRIs are a class of medications that are effective at easing depression symptoms. SNRIs are also sometimes used to treat other mental health conditions such as anxiety.
How serotonin and norepinephrine reuptake inhibitors work
Serotonin and norepinephrine reuptake inhibitors (SNRIs) ease depression by affecting chemical messengers (neurotransmitters) used to communicate between brain cells. Most antidepressants work by changing the levels of one or more of these naturally occurring brain chemicals.
SNRIs block the absorption (reuptake) of the neurotransmitters serotonin (ser-oh-TOE-nin) and norepinephrine (nor-ep-ih-NEF-rin) in the brain. They also affect certain other neurotransmitters. Changing the balance of these chemicals seems to help brain cells send and receive messages, which in turn boosts mood. Medications in this group of antidepressants are sometimes called dual reuptake inhibitors.
Serotonin and norepinephrine reuptake inhibitors approved to treat depression
SNRIs approved by the Food and Drug Administration to treat depression, with their generic names followed by brand names in parentheses, include:
- Duloxetine (Cymbalta)
- Venlafaxine (Effexor, Effexor XR)
- Desvenlafaxine (Pristiq)
As with some other antidepressants, venlafaxine is available in an immediate-release form that requires two or three doses a day and in an extended-release (XR) form that allows you to take it just once a day.
Sometimes, SNRIs are used to treat conditions other than depression.
Side effects and cautions
All SNRIs work in a similar way and generally cause similar side effects. However, each SNRI has a different chemical makeup, so one may affect you differently than does another.
Side effects of SNRIs can include:
- Nausea (particularly with duloxetine)
- Dry mouth
- Dizziness
- Insomnia
- Sleepiness
- Constipation
- Increased blood pressure (with venlafaxine)
- Excessive sweating
- Reduced sexual desire or difficulty reaching orgasm
- Inability to maintain an erection (erectile dysfunction)
- Increased heart rate
- Heart palpitation
- Difficulty urinating
- Tremor
- Headache
- Agitation or anxiety
- Changes in appetite
- Abnormal vision, such as blurred vision or double vision
- Muscle weakness
Nausea is less common with the extended-release form of SNRIs.
Next page(1 of 2)
- Schatzberg AF, et al. Antidepressants: Introduction. In: Schatzberg AF, et al. Manual of Clinical Psychopharmacology. 7th ed. Arlington, Va.: American Psychiatric Publishing; 2010. http://www.psychiatryonline.com/content.aspx?aID=600624. Accessed Oct. 5, 2010.
- Fava M, et al. Antidepressants. In: Stern TA, et al. Massachusetts General Hospital Comprehensive Clinical Psychiatry. Philadelphia, Pa.: Mosby. 2008. http://www.mdconsult.com/das/book/body/221513496-3/0/1657/421.html?tocnode=57543329&fromURL=421.html#4-u1.0-B978-0-323-04743-2..50045-7_1104. Accessed Oct. 5, 2010.
- Hirsch M, et al. http://www.uptodate.com/home/index.html. Antidepressant medication in adults: SSRIs and SNRIs. Accessed Oct. 7, 2010.
- Chew RH, et al. Selective serotonin reuptake inhibitors and mixed-action antidepressants. In: Chew RH, et al. What Your Patients Need to Know About Psychiatric Medications. 2nd ed. Washington, DC.: American Psychiatric Publishing; 2009.
- Bostwick JM. A generalist's guide to treating patients with depression with an emphasis on using side effects to tailor antidepressant therapy. Mayo Clinic Proceedings. 2010;85:538.
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