About Antidepressant Therapy

Antidepressant medications are widely used, effective treatments for depression. There are several types (classes) of antidepressant medications used to treat depressive disorders, and each of these types of medicine works a little differently.

A patient's symptoms, as well as family and medical history should be considered when selecting the initial treatment. It may take some time to find the medication that works the best for you and has the least number of side effects.

The three main classes of medications are selective serotonin reuptake inhibitors (SSRIs), monoamine oxidase inhibitors (MAOIs) , and tricyclics. There are also several newer medications that are unique in their mechanism of action.

• Selective Serotonin Reuptake Inhibitors (SSRIs)
  Clinical evidence of decreased side effects and increased safety relative to older medications have made this class of medication very popular in recent years.
  
  These medications work, as the name implies, by blocking the presynaptic serotonin transporter receptor. SSRIs are specific to serotonin (though the do have an indirect effect on norepinephrine), and thus have the advantage of not affecting histamine and acetylcholine. They are not without side effects, but their tolerability seems to be much better than the tricyclics.
  
  The five SSRI drugs currently on the market are:
  • Citalopram (Celexa)
  • Fluoxetine (Prozac)
  • Fluvoxamine (Luvox)
  • Paroxetine (Paxil)
  • Sertraline (Zoloft)

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• Monoamine Oxidase Inhibitors (MAOIs)
  MAOIs were some of the first antidepressant medications developed. The neurotransmitters responsible for mood (serotonin and norepinephrine) are also known as monoamines.
  
  Monoamine oxidase enzyme breaks these substances down. As the name implies, these medications slow down (or inhibit) the break down of serotonin and norepinephrine in the brain, allowing them to assist brain cells in sending messages for longer periods.
  
  MAOIs are no longer first-line antidepressants because of potentially fatal interactions with other medications (including cold pills). For this reason, people taking MAOIs must stay away from all restricted foods, drinks, and medications.
  
  MAOI medications include:
  • Phenelzine (Nardil)
  • Tranlycypromine (Parnate)

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• Tricyclic antidepressants (TCAs)
  These medications inhibit the nerve cell's ability to reuptake serotonin and norepinephrine, allowing a greater amount of these chemical messengers to be available for use by nerve cells.
  
  In addition to acting on norepinephrine and serotonin, tricylics have similar effects on histamine and acetylcholine, which is responsible for the troublesome side-effects associated with these medications (dry mouth, blurry vision, weight gain, and sedation). A patient's medical history must be carefully considered with tricyclics, due to the possibility of TCAs causing dizziness upon standing, rapid heartbeat, and aggravation of preexisting heart conditions.
  
  TCAs include:
  • Imipramine (Tofranil)
  • Amitriptyline (Elavil)
  • Desipramine (Norpramin)
  • Nortriptyline (Pamelor)

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• Novel Antidepressants
  Five newer medications which do not fit into the above categories are:
  • Buproprion (Wellbutrin)
  • Nefazodone (Serzone)
  • Trazodone (Desyrel)
  • Venlafaxine (Effexor)
  • Mirtazapine (Remeron)

Novel medications are usually more specific in their mechanism of action, yet they may also work on multiple neurotransmitter systems at the same time. These new-generation antidepressants show a lot of promise for helping people who have not been able to tolerate antidepressants in the past due to their lower side effect profiles.

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