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Serotonin and norepinephrine reuptake inhibitors (SNRIs)

Serotonin syndrome and SNRIs

A rare but potentially life-threatening side effect of SNRIs is serotonin syndrome. This condition, characterized by dangerously high levels of serotonin in the brain, can occur when an SNRI interacts with antidepressants called monoamine oxidase inhibitors (MAOIs). Because of this, don't take any SNRIs while you're taking any MAOIs or within two weeks of each other. Serotonin syndrome can also occur when SNRIs are taken with other medications, including:

  • Pain relief medication such as tramadol (Ultram)
  • Migraine medications such as sumatriptan (Imitrex) and rizatriptan
  • Supplements that affect serotonin levels, such as St. John's wort

Serotonin syndrome requires immediate medical treatment. Signs and symptoms include:

  • Confusion
  • Restlessness
  • Hallucinations
  • Extreme agitation
  • Fluctuations in blood pressure
  • Increased heart rate
  • Nausea and vomiting
  • Fever
  • Seizures
  • Coma

Safety concerns with SNRIs

At high doses, venlafaxine can raise blood pressure significantly. Your doctor might monitor your blood pressure regularly, especially if you already have blood pressure problems. Venlafaxine can also raise cholesterol, so you may need periodic blood tests to check your blood cholesterol. Both duloxetine and venlafaxine should be avoided or used with caution if you have narrow-angle glaucoma or raised intraocular pressure.

Use of aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs) or anticoagulants, such as warfarin (Coumadin), while taking SNRIs may increase the risk of gastrointestinal bleeding and should be monitored by your doctor.

Stopping treatment with SNRIs

SNRIs aren't considered addictive. However, stopping treatment abruptly or missing several doses can cause withdrawal-like symptoms, including:

  • Nausea
  • Headache
  • Dizziness
  • Lethargy
  • Flu-like symptoms

This is sometimes called discontinuation syndrome. Talk to your doctor before stopping so that you can gradually taper off.

Suicidal feelings and SNRIs

In some cases, antidepressants may be associated with worsening symptoms of depression or suicidal thoughts or behavior in those ages 18 to 24, particularly during the first one to two months of treatment or when you change your dosage. Be sure to talk to your doctor about any changes in your symptoms. You may need more careful monitoring when starting treatment or changing dosage, or you may need to stop the medication if your symptoms worsen. Adults age 65 and older taking antidepressants have a decreased risk of suicidal thoughts.

Talk with your doctor or mental health provider to nix your irritability, sadness or anger and improve your mood with dual reuptake inhibitor SNRIs. Feel good again.

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References
  1. FDA proposes new warnings about suicidal thinking, behavior in young adults who take antidepressant medications. U.S. Food and Drug Administration. http://www.fda.gov/bbs/topics/NEWS/2007/NEW01624.html. Accessed Sept. 12, 2008.
  2. Questions and answers on antidepressant use in children, adolescents, and adults. U.S. Food and Drug Administration. http://www.fda.gov/cder/drug/antidepressants/QA20070502.htm. Accessed Sept. 29, 2008.
  3. Lexapro (prescribing information). St. Louis, Mo.: Forest Pharmaceuticals; 2008. http://www.frx.com/pi/lexapro_pi.pdf. Accessed Oct. 9, 2008.
  4. Single interactions table. Micromedex Healthcare Series. http://www.micromedex.com. Accessed Oct. 13, 2008.
  5. Hall-Flavin DK (expert opinion). Mayo Clinic, Rochester, Minn. Oct. 1, 2008.
  6. Antidepressants: Selecting one that's right for you. MayoClinic.com. http://www.mayoclinic.com/health/antidepressants/HQ01069. Accessed Oct. 16, 2008.
  7. Buss LK (expert opinion). Mayo Clinic, Rochester, Minn. Oct. 24, 2008.
  8. Maxalt (prescribing information). Whitehouse Station, N.J.: Merck & Co.; 2008. http://www.merck.com/product/usa/pi_circulars/m/maxalt/maxalt_pi.pdf. Accessed Nov. 9, 2008.
  9. Single interactions table. Micromedex Healthcare Series. http:www.micromedex.com. Accessed Nov. 9, 2008.
  10. Imitrex (prescribing information). Research Triangle Park, N.C.: GlaxoSmithKline; 2008. http://us.gsk.com/products/assets/us_imitrex_injection.pdf. Accessed Nov. 9, 2008.
  11. Single interactions table. Micromedex Healthcare Series. http:www.micromedex.com. Accessed Nov. 9, 2008.
  12. Ultram (prescribing information). Mississaugo, Ontario, Canada: Biovail Corp.; 2007. http://www.ortho-mcneil.com/ortho-mcneil/shared/pi/ultramer.pdf. Accessed Oct. 5, 2008.
  13. Single interactions table. Micromedex Healthcare Series. http:www.micromedex.com. Accessed Oct. 14, 2008.

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Dec. 10, 2008

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