Cyclingnews ran my letter!

Yes!

Viagra - a doping product?

Rich, Sildenafil Citrate (Viagra) is also used to treat Pulmonary Arterial Hypertension. As I understand it, decreasing smooth muscle tone in the pulmonary arteries means a decrease in the afterload of the right ventricle. In turn, this means that for a given heart rate there's a greater cardiac output from the right side of the heart. The left ventricle experiences an increase in preload leading to an increase in end diastolic volume.

Without a change in contractility, the ejection fraction remains the same but the stroke volume goes up. In this way the left ventricle matches the output of the right ventricle, and the cardiac output increases. More blood oxygenated, more oxygen to the muscles.

The only odd thing is that in healthy people, the pulmonary arteries are fully dilated. I've read in the Journal of Applied Physiology that it helps at altitude, though.

Peter Chiu
New York, NY, USA
Wednesday, December 17, 2008


This letter was in response to:
Viagra - a doping product?

Viagra - a doping product? Apparently not, at least in regards to cycling. While all the witty hypotheses regarding the performance "enhancements" of taking Viagra are probably intended for entertainment purposes only, in truth they aren't far from the mark.

I suspect that some endurance athletes are taking Viagra in the hope that it will dilate their arteries, allowing more blood to flow to their muscles. More blood = more oxygen = better performance, right? However, Viagra isn't going to dilate any blood vessels in your leg muscles, or anywhere else other than its intended target. To clarify why it won't, first I should explain the way it works:

(Disclaimer: I'm not a medical professional. To those who are, please correct any inaccuracies you find below.)

-When aroused, the brain sends a signal to certain nerves in the "male anatomy" that cause the body to produce Nitric Oxide.
-This Nitric Oxide causes certain enzymes to start producing Cyclic Guanosine Monophosphate (cGMP).
-cGMP causes the smooth muscle cells in the artery walls to relax, allowing more blood to flow into the "male anatomy", which results in an erection.
-There is a second enzyme also present, Phosphodiesterase (PDE), that breaks the cGMP back down, preventing an uncontrollable reaction.
-All of this occurs only when the brain sends the proper signal, ie "I'm aroused".
-One of the most common reasons for erectile dysfunction is that the body is not producing enough cGMP. One way to counteract this is to increase the amount of cGMP in the blood by preventing the PDE from breaking it down. That is what Viagra does, it effectively blocks the PDE from doing its job, allowing cGMP to accumulate and do its job.
-Viagra is flushed out of the body in about four hours, making this a temporary effect.

Now, you might be thinking that Viagra sounds like the perfect way to increase blood flow to ALL of your body, but here's the kicker:

There are eleven types of PDE in the body, each effective in different areas. In the case of the "male anatomy", PDE5 is the specific type of PDE that works as described above. Viagra ONLY blocks PDE5, and has no effect on any other vascular muscle cells, including those in the legs, lungs, and heart. In other words, it has no performance-enhancing effect in endurance sports.

Frankly, I'm astonished that no one at WADA knows this. In theory, one could figure out the necessary chemical needed to block whatever form of PDE that is used to control the dilation of the blood vessels in the muscles used in endurance sports, but whatever it is it wouldn't be Sildenafil Citrate, aka Viagra. It looks like WADA is barking up the wrong tree.

Rich Nickla
Encinitas, CA, USA
Thursday, December 11, 2008


Pwned. Wut.

The two guys above my letter have MD's. One is a cardiologist; the other is a cardiothoracic surgeon. Is that pwned x3? I think so.