New Type of SSRI: Help for Fibromyalgia & Chronic Fatigue Syndrome?

The U.S. FDA has approved a new type of antidepressant called Viibryd (vilazodone) that may offer relief with fewer side effects, especially weight gain and sexual dysfunction. The trick is targeting more than reuptake.

This drug hasn't specifically been tested for fibromyalgia or chronic fatigue syndrome, but antidepressants are the most commonly prescribed drugs for these conditions. Like Viibryd, many of those antidepressants are aimed at slowing a process called re-uptake.

These drugs are called SSRIs (selective serotonin reuptake inhibitors) or SNRIs (serotonin norepinephrine reuptake inhibitors.)

Reuptake is basically a housekeeping function of the brain. When one neuron (brain cell) sends a message to another, it does so with chemicals called neurotransmitters, and serotonin is a very important one to us, as we typically don't have enough or don't use it properly.

When you have low serotonin (or any neurotransmitter), a message sent using it doesn't have enough power to get from one neuron to the next. It's like a tennis serve that's too weak to get the ball across the net. The ball boy that runs out to collect these unreceived balls is doing the job of reuptake -- getting rid of the used serotonin so it's not cluttering things up.

Drugs that slow reuptake keep that ball boy (actually glial cells) from snatching away the neurotransmitter and giving it more time to deliver its message.

But so far, we've only looked at one side of the tennis court. What about the guy across the net, the neuron who's receiving the message? That cell is called the receptor, and each receptor is designed to only receive messages sent by certain neurotransmitters. Basically, the receptor is locked, and only the right chemical keys can open it.

This new drug targets certain serotonin receptors with simulated keys and tricks them into opening, making it easier for the messages to flow from cell to cell.

What we're seeing is that as drugs become more specialized in this way, they continue to be effective with fewer side effects. By zeroing in on specific and limited ways that the brain functions, they can be better target the underlying problem instead of changing the function of larger areas of the brain that control things we don't want to mess with.

Please don't think that I'm recommending this drug, because I'm really not. I just get excited about the neurology behind these things, and this could be an important change for you if side effects have made you turn away from SSRI/SNRIs.

And this drug isn't side-effect free, by any means. In trials, common side effects included diarrhea, nausea, dizziness, insomnia, abnormal dreams and vomiting. Unlike many antidepressants, in trials Viibryd didn't appear to have sexual side effects or cause weight gain -- two symptoms that frequently lead people to stop taking them.

If you're considering Viibryd, be sure to talk to your doctor and pharmacist about the possible risk and benefits as well as potential interactions with other medications you're taking.

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