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Selective serotonin reuptake inhibitors (SSRIs)

SSRIs, a popular antidepressant type, can help you overcome depression symptoms and feel good again. Discover how Prozac and other SSRIs boost your mood and what side effects they may cause.

By Mayo Clinic staff

Selective serotonin reuptake inhibitors (SSRIs) are a popular class of antidepressant medications. The first drug in this class was fluoxetine (Prozac), which hit the U.S. market in 1987.

How SSRIs work

Precisely how SSRIs affect depression isn't clear. Certain brain chemicals called neurotransmitters are associated with depression, including the neurotransmitter serotonin (ser-oh-TOE-nin). Some research suggests that abnormalities in neurotransmitter activity affect mood and behavior. SSRIs seem to relieve symptoms of depression by blocking the reabsorption (reuptake) of serotonin by certain nerve cells in the brain. This leaves more serotonin available in the brain. Increased serotonin enhances neurotransmission — the sending of nerve impulses — and improves mood. SSRIs are called selective because they seem to affect only serotonin, not other neurotransmitters.

Antidepressants, in general, may also work by playing a neuroprotective role in how they relieve anxiety and depression. It's thought that antidepressants may increase the effects of brain receptors that help nerve cells keep sensitivity to glutamate — an organic compound of a nonessential amino acid — in check. This increased support of nerve cells lowers glutamate sensitivity, providing protection against the glutamate overwhelming and exciting key brain areas related to anxiety and depression.

Therapeutic effects of antidepressants may vary in people, due in part to each person's genetic makeup. It's thought that people's sensitivity to antidepressant effects, especially selective serotonin reuptake inhibitor effects, can vary depending on:

  • How each person's serotonin reuptake receptor function works
  • His or her alleles — the parts of chromosomes that determine inherited characteristics, such as height and hair color, which combine to make each person unique

Antidepressant medications are often the first treatment choice for adults with moderate or severe depression, sometimes along with psychotherapy. Although antidepressants may not cure depression, they can help you achieve remission — the disappearance or nearly complete reduction of depression symptoms.

SSRIs approved to treat depression

Some SSRIs are available in extended-release form or controlled-release form, often designated with the letters XR or CR. These forms provide controlled release of the medication throughout the day or for a week at a time with a single dose.

Here are the SSRIs approved by the Food and Drug Administration (FDA) specifically to treat depression, with their generic, or chemical, names followed by available brand names in parentheses:

  • Citalopram (Celexa)
  • Escitalopram (Lexapro)
  • Fluoxetine (Prozac, Prozac Weekly)
  • Paroxetine (Paxil, Paxil CR, Pexeva)
  • Sertraline (Zoloft)

Also, an olanzapine and fluoxetine combination (Symbyax) recently received FDA approval for treating bipolar depression. Symbyax is classed as both an SSRI antidepressant and an atypical antipsychotic.

These medications may also be used to treat conditions other than depression.

Side effects of SSRIs

All SSRIs have the same general mechanism of action and side effects. However, individual SSRIs have some different pharmacological characteristics. That means you may respond differently to certain SSRIs or have different side effects with different SSRIs. For instance, you may have unpleasant side effects with one SSRI but not another. Also, they're less likely to have adverse interactions with other medications and are less dangerous if taken as an overdose.

Side effects of SSRIs include:

  • Nausea
  • Sexual dysfunction, including reduced desire or orgasm difficulties
  • Dry mouth
  • Headache
  • Diarrhea
  • Nervousness
  • Rash
  • Agitation
  • Restlessness
  • Increased sweating
  • Weight gain
  • Drowsiness
  • Insomnia

You may experience less nausea with extended- and controlled-release forms of SSRIs.

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References
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  7. Symbyax ... because not all depression is the same. http://www.symbyax.com/index.jsp. Accessed Oct. 6, 2008.
  8. Antidepressants: Selecting one that's right for you. MayoClinic.com. http://www.mayoclinic.com/health/antidepressants/HQ01069. Accessed Oct. 16, 2008.
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  10. Ultram (prescribing information). Mississaugo, Ontario, Canada: Biovail Corp.; 2007. http://www.ortho-mcneil.com/ortho-mcneil/shared/pi/ultramer.pdf. Accessed Oct. 5, 2008.
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  12. Imitrex (prescribing information). Research Triangle Park, N.C.: GlaxoSmithKline; 2008. http://us.gsk.com/products/assets/us_imitrex_injection.pdf. Accessed Nov. 9, 2008.
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Dec. 10, 2008

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