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I take Nexium for acid reflux and I just got some C4 Mass Preworkout powder. On the casing of the C4 it says "Do not take ... if you're on nitrates for chest pain"

I didn't think that was what I was on, but later that night my chest was on fire and my throat felt like it was closing up. I'm not sure if it had anything to do with the C4 or the Nexium, but I would like to know.

  • My guess is that the preworkout powder contains an ingestible nitric oxide donor (NO) or substrate for nitric oxide synthase (NOS). NO is a physiologically occurring molecule with a panoply of physiologic effects both beneficial and harmful. NO is the most potent vasodilating substance known (massive NO release is the cause for hemodynamic shock in severe bacterial sepsis). When used during exercise, the idea is that boosting NO production will increase blood flow to muscles, thereby enhancing their recovery and development. Nitrates are also NO donors, hence the caution. – scottb Jul 10 '15 at 1:59
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No. Nexium is the trade name of a generic drug called esomeprazole, a proton pump inhibitor used to treat gastro-esophageal acid reflux. “Nitrates for chest pain” refers to the class of cardiac drugs that share a similar biochemical structure structure and pharmacologic mechanism, which involves conversion to nitric oxide. In the U.S., the available nitrates are:

  • nitroglycerin
  • isosorbide mononitrate
  • isosorbide dinitrate

These are vasodilators, used for anginal chest pain, usually in combination with beta blockers. They work by dilating the arteries around the heart and improving blood flow.

A google search reveals that C4 is a dietary supplement that contains caffeine. I suspect that the warning about nitrates has to do more with identifying people who have cardiac problems (which could be exacerbated by caffeine) than any specific drug interaction.

I have no idea why your chest was on fire, and this site is not a good place to try to find out. You should certainly discuss this with your doctor if you’re concerned.

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