Also known as dual-uptake inhibitors, serotonin and norepinephrine reuptake inhibitors (SNRIs) prevent the absorption of important chemical messengers in the brain. Over time, the amount of serotonin and norepinephrine in the brain increases, which scientists believe helps improve mood and reduce anxiety. These chemical messengers, or neurotransmitters, are responsible for regulating other mental and physical processes besides emotional state. Sometimes SNRIs are prescribed for the treatment of health problems seemingly unrelated to depression or anxiety. Chronic pain conditions, such as fibromyalgia, have responded well to certain SNRI medications, although researchers don't completely know why.
SNRIs are very similar to another category of antidepressants known as selective serotonin reuptake inhibitors but with a slightly broader effect on chemical processes in the brain. Examples of SNRIs include Cymbalta (duloxetine), Effexor (venlafaxine), and Pristiq (desvenlafaxine). Effexor is available in both an immediate- and extended-release formula. Certain mental health issues will benefit more from one or the other. In some cases, it's a matter of trial and error to discover the best SNRI for a particular treatment situation.
Scientists are only beginning to understand all of the functions that serotonin and norepinephrine perform in the human brain. Because neurotransmitters are so involved in all physiological activities, all antidepressants carry some risk of unwanted side effects. The most common side effects of SNRIs include dry mouth, dizziness, insomnia, and constipation. Cymbalta is associated with nausea more so than its counterparts. Elevated blood pressure is a typical side effect of Effexor. As is the case with all antidepressant medications, everyone responds differently to these drugs and may experience a different set of side effects. Most people, however, experience minor and insignificant side effects and have no problem following their doctors' prescriptions.
There is no potential for abuse or addiction with SNRIs. Nevertheless, suddenly discontinuing an SNRI medication may lead to unpleasant withdrawal symptoms. These include nausea, headache, lethargy, and even flulike symptoms. Doctors usually "wean" patients off an SNRI prescription rather than stopping all at once.
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