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SSRIs (as described under Fatigue and Cognitive Function above) are also prescribed to help stabilize mood and/or reduce depression. The newer formulas will target other neurotransmitters along with serotonin, like norepinephrine. These are categorized as selective serotonin and norepinephrine reuptake inhibitors (SNRIs), Norepinephrine Serotonin Reuptake Inhibitors (NSRIs) and those primarily adjusting norepinephrine release are referred to as norepinephrine reuptake inhibitors (NRIs). These neurotransmitters have been found to affect pain, sleep, fatigue, cognitive as well as mood disturbance; therefore, adjusting these may provide improvement of these symptoms.
One of the newest SNRIs on the market is Cymbalta (duloxetine). Cymbalta's initial use was to treat major depression and anxiety. It has other properties which help to relieve nerve pain as well as improve one's mood, sleep, energy level, and decrease nervousness and as a result, the FDA approved its use for FM. Effexor (venlafaxine) was one of the first SNRIs which came out in 1993. This type of medication (as well as some benzodiazepines and sleeping pills) can be very sensitive to sudden interruption of use and may produce "brain sparks /shivers" in some patients (described as electric shock-like sensations in their brain but also extending to parts of the body, sometimes along with feeling of disorientation, vertigo and/or lightheadedness). Therefore, when any of these types of medications need to be discontinued, they should be tapered off gradually.
Milnacipran is the first NSRI to come on the market and it is different from Cymbalta, an SNRI, and older SSRIs, since it affects norepinephrine and serotonin in a more equal/ balanced way. During clinical trials, it was found to cause fewer undesirable side effects (such as sexual dysfunction). In January 2009, the FDA approved milnacipran for the management of FM, which will be sold under the brand name of Savella. It is expected to be available by prescription around March 2009. Reboxetine is another drug being studied in patients with FM. It is an NRI and currently used outside the US as treatment of depression.