What are SSRI's ?

When brain cells (called neurons) send signals to one another, they release a little bit of a neurotransmitter so that the message can be delivered. They then have to take back the neurotransmitter they released so they can send the next message. This process of replacing the neurotransmitter is called “reuptake.”
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SSRI's or Selective Serotonin Reuptake Inhibitors, are a class of antidepressant medications that are used to treat major depressive disorders.  They block the reuptake of serotonin in the synaptic cleft thus increasing the concentration of serotonin.

If you’re struggling with depression, the areas of your brain that regulate mood and send messages using serotonin might not function properly. SSRIs help make more serotonin available by blocking the reuptake process. This allows serotonin to build up between neurons so messages can be sent correctly. They’re called “selective” serotonin reuptake inhibitors because they specifically target serotonin.

There are 6 members of the SSRI family:  fluoxetine (Prozac), sertraline (Zoloft), citalopram (Celexa), escitalopram (Lexapro),  paraxotine (Paxil), and fluvoxamine (Luvox) and the newest member, vilazodone (Viibryd).

There are similarities and difference with each antidepressant that can be used to customize the selection of one antidepressant over another.  The SSRI's are most similar in that their primary mechanism is to inhibit the reuptake of the serotonin transporter.  There are secondary properties that differ with each molecule in that some also act on other mechanisms such as action on dopamine receptors, post synaptic serotonin receptors, sigma receptors and action on enzymes that metabolize the medications.

However, the most important clinical consideration in picking an antidepressant is their side effect profile.  All of the antidepressants named above have effects on energy and appetite.  Some members boost energy such as fluoxetine and sertraline.  Others are more sedating such as citalopram, escitalopram, paroxetine and fluvoxamine.  Vilazodone, neither boosts energy nor is sedating .

Appetite changes are also an important consideration.  All of the SSRI's promote weight gain, most especially paroxetine and fluvoxamine.  Weight changes could range between 5-15 lbs and therefore can be significant potential side effect to consider.  However, vilazodone, is considered to be weight neutral.

Price is an important financial consideration.  With the exception of vilazodone, all of the SSRI's are generic and are relatively very inexpensive.  Vilazodone, however, is newer and is considerably more expensive.  However, given its efficacy and more favorable side effect profile, one can argue about its advantages that can balance it's price. 
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All in all, SSRI's are a good first line choice to treat major depressive disorders.  Efficacy, side effects and price are variables that one needs to consider to make an educated choice. 
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