Serotonin and norepinephrine reuptake inhibitors (SNRIs)

Antidepressant SNRIs help relieve depression symptoms, such as irritability and sadness, but some are also used for anxiety disorders and nerve pain. Here's how they work and what side effects they may cause.

By Mayo Clinic Staff

Serotonin and norepinephrine reuptake inhibitors (SNRIs) are a class of medications that are effective in treating depression. SNRIs are also sometimes used to treat other conditions, such as anxiety disorders and long-term (chronic) pain, especially nerve pain. SNRIs may be helpful if you have chronic pain in addition to depression.

How SNRIs work

SNRIs ease depression by impacting chemical messengers (neurotransmitters) used to communicate between brain cells. Like most antidepressants, SNRIs work by ultimately effecting changes in brain chemistry and communication in brain nerve cell circuitry known to regulate mood, to help relieve depression.

SNRIs block the reabsorption (reuptake) of the neurotransmitters serotonin (ser-o-TOE-nin) and norepinephrine (nor-ep-ih-NEF-rin) in the brain.

SNRIs approved to treat depression

The Food and Drug Administration (FDA) has approved these SNRIs to treat depression:

  • Desvenlafaxine (Pristiq, Khedezla)
  • Duloxetine (Cymbalta) ― also approved to treat anxiety and certain types of chronic pain
  • Levomilnacipran (Fetzima)
  • Venlafaxine (Effexor XR) ― also approved to treat anxiety and panic disorder

Side effects and cautions

All SNRIs work in a similar way and generally can cause similar side effects, though some people may not experience any side effects. Side effects are usually mild and go away after the first few weeks of treatment. Taking your medication with food may reduce nausea. If you can't tolerate one SNRI, you may be able to tolerate a different one, as each SNRI varies in chemical makeup.

The most common possible side effects of SNRIs include:

  • Nausea
  • Dry mouth
  • Dizziness
  • Headache
  • Excessive sweating

Other possible side effects may include:

  • Tiredness
  • Constipation
  • Insomnia
  • Changes in sexual function, such as reduced sexual desire, difficulty reaching orgasm or the inability to maintain an erection (erectile dysfunction)
  • Loss of appetite

Typically the benefits of antidepressants outweigh the possible side effects. Which antidepressant is best for you depends on a number of issues, such as your symptoms and any other health conditions you may have.

Ask your doctor and pharmacist about the most common possible side effects for your specific SNRI and read the patient medication guide that comes with the prescription.

June 21, 2016 See more In-depth