Serotonin and Norepinephrine Reuptake Inhibitors (SNRIs)

What are Serotonin and Norepinephrine Reuptake Inhibitors (SRNIs)?

Serotonin norepinephrine reuptake inhibitors (SNRIs) are a class of antidepressant used in the treatment of clinical depression and other affective disorders. They are also sometimes used to treat anxiety disorders, obsessive-compulsive disorder, attention deficit hyperactivity disorder (ADHD) and chronic neuropathic pain.

Mechanism of Action of Serotonin and Norepinephrine Reuptake Inhibitors (SNRIs)

The precise mechanism of action of Serotonin and norepinephrine reuptake inhibitors (SNRIs) is not clear. However it is thought that the increased levels of Serotonin and Norepinephrine enhance neurotransmission (the sending of nerve impulses), thereby improving and elevating mood. Medications in this group are sometimes known as dual reuptake inhibitors. Serotonin and Norepinephrine are associated with depression, and abnormalities in activity of these neurotransmitters can affect mood and behavior.

Examples of Serotonin and Norepinephrine Reuptake Inhibitors (SNRIs)

The following Serotonin and Norepinephrine Reuptake Inhibitors (SNRIs) have been approved by the Food and Drug Administration specifically to treat depression:

• Cymbalta (Duloxetine) - a new SNRI by Eli Lilly approved for the treatment of depression and neuropathic pain
• Effexor and Effexor XR (Venlafaxine) - the first and most commonly used SNRI

Generic Cymbalta and Generic Effexor XR are also available.

Side effects of Serotonin and Norepinephrine Reuptake Inhibitors (SRNIs)

Side effects of Serotonin and Norepinephrine Reuptake Inhibitors (SNRIs) may include:

• Nausea and vomiting
• Dizziness
• Insomnia
• Sleepiness
• Trouble sleeping
• Abnormal dreams
• Constipation
• Sweating
• Dry mouth
• Yawning
• Tremor
• Gas
• Anxiety or agitation
• Abnormal vision, such as blurred vision or double vision
• Headache
• Sexual dysfunction

Stopping treatment with Serotonin and Norepinephrine Reuptake Inhibitors (SRNIs), especially when done suddenly, can cause withdrawal-like symptoms, including nausea, anxiety, diarrhea, confusion, agitation, headaches, nightmares, coordination changes, and skin tingling or shock-like sensations. This is sometimes called discontinuation syndrome. Talk to your doctor before stopping medication so that you can taper off gradually.

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. Venlafaxine should be avoided or used with caution if you have narrow-angle glaucoma or raised intraocular pressure.

In some cases, antidepressants may be associated with worsening symptoms of depression or suicidal thoughts or behavior, particularly early in 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 at the beginning of treatment or upon a change in treatment, or you may need to stop the medication if your symptoms worsen.