Antidepressants are medications for treating anxiety and depressive disorders. They work by interfering with the neurotransmitter levels in the brain, thus improving the patient's mood and decreasing the symptoms of the mood disorder. Multiple classifications of antidepressants are available; each works on separate neurotransmitters and can affect each patient differently; therefore a patient may need to try more than one antidepressant under the guidance of her doctor to see what works best.
Reuptake Inhibitors
Reuptake inhibitors work by preventing the reuptake of one or more neurotransmitters, leaving more to be used by the brain. Reuptake inhibitors are available in two types: selective reuptake inhibitors and dual reuptake inhibitors. Selective serotonin reuptake inhibitors (SSRIs) target serotonin and are the first medication choice for depression, according to the Mayo Clinic. Sertraline, citalopram, paroxetine, escitalopram and fluoxetine are SSRIs approved for depression by the Food and Drug Administration (FDA).
Serotonin and norepinephrine reuptake inhibitors (SNRIs) and norepinephrine and dopamine reuptake inhibitors (NDRIs) are both dual reuptake inhibitors, because they both target two neurotransmitters. Two SNRIs are approved for depression: duloxetine and venlafaxine; only one NDRI, bupropion, is FDA approved. Reuptake inhibitors have the least number of side effects compared to other antidepressants.
Cyclic Antidepressants
Cyclic antidepressants are another group of antidepressants, and they have a different chemical structure than reuptake inhibitors. Tricyclic antidepressants are an older form of antidepressant that mainly prevents the reuptake of serotonin and norepinephrine; the Mayo Clinic adds that to a lesser extent, tricyclic antidepressants also prevent the reuptake of dopamine. Amitriptyline, trimipramine, amoxapine, protriptyline, desipramine, nortriptyline, doxepine and imipramine are all approved by the FDA for depression. Tricyclic antidepressants have more side effects than reuptake inhibitors.
Another type of cyclic antidepressant, tetracyclic antidepressants work by preventing neurotransmitters from binding to the alpha-2 receptors, which increases the amount of serotonin and norepinephrine in the brain. Mirtazapine is the tetracyclic antidepressant approved by the FDA for depression.
Monoamine Oxidase Inhibitors
The oldest manufactured antidepressant, MAOIs prevent "the enzyme monoamine oxidase from metabolizing the neurotransmitters norepinephrine, serotonin and dopamine," according to the Mayo Clinic. Phenelzine, selegiline, tranylcypromine and isocarboxazid are approved by the FDA for depression, with selegiline being the first antidepressant available as a transdermal patch. MAOIs, however, have the most side effects of all the antidepressants, and users are required to follow a strict diet.
