Depression is a psychological disorder characterized by extremely low or sad moods that affect both physical and social activities. It is commonly believed that depression may be caused by an imbalance of chemicals, such as serotonin, norepinephrine or dopamine, in the brain. There are several medications classified based on the chemicals they affect-- selective serotonin reuptake inhibitors, serotonin and norepinephrine reuptake inhibitors, tricyclic antidepressants, monoamine oxidase inhibitors and atypical antidepressants--that are often prescribed to treat depression.
Selective Serotonin Reuptake Inhibitors (SSRIs)
Serotonin, a chemical in the brain, helps to regulate emotional, behavioral and cognitive processes. A low level of serotonin may be a contributing factor to depression, according to the Mayo Clinic.
Serotonin in the brain is continually removed from the nerve cells and taken back up the nerve fiber to where it originated. This is referred to a serotonin reuptake. The more serotonin that undergoes this reuptake, the less is available in the brain to work as a neurotransmitter sending signals between nerves.
Selective serotonin reuptake inhibitors block this serotonin reuptake process, leaving more serotonin free. There are many different SSRI prescription medications, including citalopram, escitalopram, fluoxetine, paroxetine and sertraline.
Serotonin and Norepinephrine Reuptake Inhibitors (SNRIs)
Norepinephrine, another chemical in the brain important for emotions, attentiveness and learning, also undergoes a reuptake process similar to serotonin. Serotonin and norepinephrine reuptake inhibitors work to block the reuptake of both serotonin and norepinephrine. Venalfaxine, desvenalfaxine and duloxetine are all serotonin and norepinephrine reuptake inhibitors that work to increase the levels of these chemicals in the brain, thereby relieving depression.
Tricyclic Antidepressants
Tricyclic antidepressants work by blocking the reuptake of serotonin, norepinephrine and dopamine, another chemical in the brain that helps to regulate moods. These medications were among the first antidepressants developed, according to the Mayo Clinic, and although they cause a variety of side effects, are still prescribed today. Medications including imipramine, amitriptyline, trimipramine and doxepin all belong to this classification of antidepressants.
Monoamine Oxidase Inhibitors (MAOIs)
Monoamine oxidase inhibitor medications prevent the enzyme monoamine oxidase from breaking down important neurotransmitters, including serotonin, norepinephrine and dopamine, thereby increasing the levels of these chemicals and boosting mood. These medications, including isocarboxazid, phenelzine, tranylcypromine and selegiline are all powerful antidepressants, but can induce potentially dangerous side effects.
Atypical Antidepressants
Atypical antidepressant is a classification that includes all the medications that do not fit into the other categories. Bupropion, trazodone, mirtazapine and nefazodone all belong to this classification, and are effective in treating the symptoms of depression in some patients.
