What is an SNRI?

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  • Written By: Misty Wiser
  • Edited By: Allegra J. Lingo
  • Last Modified Date: 05 October 2019
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Serotonin and norepinephrine reuptake inhibitors (SNRI) is a class of antidepressant medications. This type of medicine prevents the neurotransmitters serotonin and norepinephrine from being reabsorbed into neurons during a process called reuptake. In addition to depression, these medications may be used to treat anxiety and panic disorders, obsessive-compulsive disorder (OCD), anorexia, and bulimia. It is also prescribed to relieve the pain of some forms of neuropathy, including diabetic neuropathy.

Mood disorders are thought to be caused by an inability of the brain to utilize all of the serotonin and norepinephrine it produces. These neurotransmitters are responsible for sending messages between the neurons through pathways called synapses. When there are not enough of these neurotransmitters to complete the message transfer, the message is garbled. This can result in unwanted behaviors and mood processes.

SNRI medications do not cause the brain to create additional serotonin and norepinephrine, but instead allow all of the neurotransmitters naturally produced by the brain cells to be used. They are designed to prevent the neurotransmitters leftover in the synapses from being reabsorbed into the brain cells. The additional amount of serotonin and norepinephrine left circulating in the synapses is thought to improve mood and other behavioral disorders.


It usually requires at least two or three weeks of daily medication before the beneficial effects of the SNRI medications are felt. During the introduction of the medication, a person may feel very tired and nauseous. These sensations generally pass shortly after the two weeks have ended.

Most of the other side effects of the medicine are mild and not bothersome enough to stop taking the medicine. Many people have dry mouth, hand tremors, and an increase in headaches accompanied by sensitivity to light when taking an SNRI. Constipation is another commonly reported side effect. Some may notice excessive sweating occurs after starting the medication.

Sexual side effects are common when taking an SNRI. Men may have difficulty getting and keeping an erection long enough for sexual activity. Some women report a lack of desire for intimacy and an inability to achieve orgasm while taking the antidepressant.

A few side effects of the SNRI class of medications could be harmful and should be reported to a medical professional. Heart palpitations and tachycardia, an increase in the heart rate, is an unwanted result in some people taking the medication. Any blurry or double vision experienced while on an SNRI should be investigated. If excessive sleepiness or insomnia continue after the introductory period, a different antidepressant may need to be prescribed.

An SNRI should not be discontinued without a doctor’s supervision. Suddenly stopping the medication can cause nausea, tiredness, dizziness, and extreme headaches. Some people experience the sensation of an electric shock. The medicine needs to be reduced slowly in stages to avoid these adverse effects.


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