Selective Serotonin and Norepinephrine Reuptake Inhibitors (SNRIs)
Newer antidepressants (known as selective serotonin and norepinephrine reuptake inhibitors, or serotonin-norepinephrine reuptake inhibitors, or SNRIs for short) affect serotonin, as well as as norepinephrine and other neurotransmitter systems such as dopamine. SNRIs work like SSRIs in that they inhibit the reuptake of neurotransmitters at the synaptic junction.
Trazodone (Desyrel) inhibits serotonin reuptake in addition to blocking certain types of serotonin, norepinephrine, and histamine receptors. Histamine is a both a biological chemical involved in immune responses as well as a neurotransmitter. In low doses, Trazodone can be used as a sleep aid, especially for people who experience insomnia as part of their depression. Side effects of Trazodone include: allergic reactions, irregular heartbeat, prolonged and painful erection, drowsiness, fatigue, lethargy (exhaustion), psychomotor retardation (slow movements), lightheadedness, dizziness, difficulty concentrating, confusion, impaired memory, disorientation, excitement, agitation, anxiety, tension, nervousness, restlessness, insomnia, nightmares, anger, hostility and, rarely, hypomania, visual distortions, hallucinations (sensing things that aren't really there), delusions (false, fixed beliefs), and paranoia (suspicious fear).
Buproprion (Wellbutrin) is often a first choice treatment for Major Depressive Disorder. This medication is just as effective as SSRIs in treating depressive symptoms, with less risk of weight gain and sexual side effects. In addition to serotonin and norepinephrine, buproprion also inhibits dopamine reuptake. The most common side effects of buproprion are dry mouth, constipation, headaches, and insomnia. Care must be taken when using buproprion at higher doses, as it has been known to cause seizures.
Venlafaxine (Effexor) is often used for the treatment of depressive illnesses, but large numbers of studies demonstrating treatment success are lacking. In addition to inhibiting serotonin reuptake, venlafaxine inhibits norepinephrine and dopamine reuptake. Venlafaxine does not interfere with other brain chemicals, which makes it less "messy" and more powerful than other antidepressants. Some evidence suggests that venlafaxine relieves depressive symptoms more quickly than other medications with fewer side effects, and that it can be combined safely with other medications. However, more research is necessary to substantiate these claims.
Nefazodone (Serzone) inhibits serotonin reuptake by blocking a particular type of serotonin receptor. Serzone is sedating, and is useful for relieving anxiety and severe insomnia. Furthermore, sexual side effects are mild, if any. Unfortunately however, nefazodone is a strong inhibitor of liver enzymes and should be used cautiously. Many medications are metabolized in the liver, and functional liver enzymes are essential to proper liver functioning and overall health.
Mirtazapine (Remeron) blocks serotonin and norepinephrine reuptake. Mirtazapine is sedating, and has the disagreeable side effect (for most) of weight gain in comparison with other SSRIs. Although few studies clearly demonstrate Mirtazapine's usefulness in treating unipolar depression, this medication may be a good option for people who have experienced significant weight loss during their depressive episodes.