Serotonin and norepinephrine reuptake inhibitors (SNRIs)

Antidepressant SNRIs help relieve depression symptoms, such as irritability and sadness. 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 at easing depression symptoms. SNRIs are also sometimes used to treat other conditions such as anxiety and nerve pain.

How SNRIs work

Serotonin (ser-o-TOE-nin) and norepinephrine (nor-ep-ih-NEF-rin) reuptake inhibitors ease depression by affecting chemical messengers (neurotransmitters) used to communicate between brain cells. Like most antidepressants, SNRIs work by changing the levels of one or more of these naturally occurring brain chemicals.

SNRIs block the absorption (reuptake) of the neurotransmitters serotonin and norepinephrine 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-action antidepressants.

SNRIs approved to treat depression

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

  • Duloxetine (Cymbalta)
  • Venlafaxine (Effexor XR)
  • Desvenlafaxine (Pristiq)

Side effects and cautions

All SNRIs work in a similar way and generally cause similar side effects. However, each SNRI varies in chemical makeup, so one may affect you differently than another does. Side effects are usually mild and go away after the first few weeks of treatment. Taking your medication with food may decrease nausea.

The most common side effects of SNRIs include:

  • Nausea
  • Dry mouth
  • Dizziness
  • Excessive sweating

Other side effects may include:

  • Tiredness
  • Difficulty urinating
  • Agitation or anxiety
  • Constipation
  • Insomnia
  • Sexual problems, such as reduced sexual desire, difficulty reaching orgasm, or the inability to maintain an erection (erectile dysfunction)
  • Headache
  • Loss of appetite

Read the package insert for additional side effects and talk to your doctor or pharmacist if you have questions.

June 26, 2013 See more In-depth