A serotonin-norepinephrine reuptake inhibitor (SNRI) is a medication principally used to treat depression or related anxiety disorders. SNRIs accomplish reduction in depressive or anxious symptoms by preventing the body from utilization or reuptake of the neurotransmitters, norepinephrine and serotonin. Since the body is not consuming these neurotransmitters rapidly, it can lead to establishment of greater mood regulation, as more free serotonin and norepinephrine are available. The medications presently considered to belong to the serotonin-norepinephrine reuptake inhibitor class include Cymbalta® (duloxetine), Pristiq® (desvenlafaxine) and Effexor® (venlafaxine). Like all medications they have benefits and side effects and are not always the appropriate treatment.
SNRIs are thought of as “newer” antidepressants, differing slightly in action from selective serotonin reuptake inhibitors (SSRIs). SSRIs only prevent the reuptake of serotonin and have limited action on norepinephrine reuptake inhibition. While the present medications are recent in development, there is a class of antidepressants that have similar action to the modern serotonin-norepinephrine reuptake inhibitor. Many tricyclic antidepressants like amitriptyline, clomipramine, and doxepin inhibit the reuptake of both serotonin and norepinephrine. Tricyclics tend to have a higher side effect profile and have been replaced, for the most part by SNRIs and SSRIs, though they still pose an option for treatment if response to more recent drugs is not favorable.
In both previous and reincarnated form, the serotonin-norepinephrine reuptake inhibitor has proven that depression or anxiety can be caused by more than inadequate free serotonin. Some patients respond readily to SNRIs when they have failed to adequately respond to SSRIs. Nevertheless, not all depression or anxiety is adequately treated by one of these medicines, and SNRIs tend to have a significant side effect profile that may discourage people from remaining on them.
Some of the most common side effects of serotonin-norepinephrine reuptake inhibitor medications include nausea, constipation, palpitations, higher heart rate, increased anxiety, high blood pressure, profuse perspiration, dry mouth and eyes, dizziness, headache, and sexual dysfunction like erectile dysfunction, inability to achieve orgasm, and disinterest in sex. Not all users experience all side effects and not all users experience benefits. It takes about two to six weeks to determine if a medication will be effective.
There is an additional peculiarity associated with serotonin-norepinephrine reuptake inhibitor drugs. They have a tendency to cause dependency, which is less associated with SSRIs, though it can happen. The release of SSRIs and SNRIs was initially championed because they were thought not to create withdrawal. Significant study into this matter has now shown that especially medications like venlafaxine and desvenlafaxine are associated with a high number of withdrawal symptoms, including a peculiar feeling of “brain zap,” which is described as an electrical charge or buzz in the head.
These symptoms can usually be avoided if medication is slowly tapered off. Tapering poses some problems because a person needing to discontinue the medication may still be in need of SSRI or SNRI treatment, and during the tapering phase, it is usually not appropriate to add another medication. Still, without tapering, incidence of unpleasant side effects can be extremely high.