Antinausea syrup and soda pop have many of the same ingredients- what's the difference?

I purchased an Nausea control liquid syrup product made by Valu-Rite at a local pharmacy. The active ingredients are : phosphoric acid, dextrose (glucose), levulose (fructose), with a few inactive ingredients like glycerin and food coloring.

These ingredients don't sound much different than the corn syrup and phosphoric acid in carbonated sodas. Maybe I should have just bought a can of pop?

Mild nausea caused by stomach irritation is often treated with a 'phosphorylated carbohydrate syrup'. As you've noticed, the composition of the syrup is very similar to soda pop. You'll get essentially the same benefits from the pop, but there are a few differences:

  • The bubbles in carbonated drinks are a source of stomach irritation, so you'll have to let the pop go flat before using it for this purpose.
  • The syrup probably does a better job of coating the stomach than the pop would.
  • The syrup doesn't contain caffeine, while some pop does.

Additional acid contributes to irritation. So why doesn't the phosphoric acid irritate the stomach? At high concentrations, it's nasty stuff. The phosphoric acid in the syrup is very dilute, and it is not fully protonated (if the syrup has a pH of around 2.5-3, it's mostly H2PO4- with a smaller amount of H3PO4). The phosphoric acid has a pK1 of 7.5× 10-3) and so can buffer as H3PO4/H2PO4- around a pH of 2.1. The pH of normal stomach contents is typically lower than this (about 1.6 to 1.8). So the phosphoric acid in the syrup won't lower stomach pH by dissociating.

You might want to visit Quickcare's resource for more information about nausea prevention. They specifically suggest flat soda pop, non-acidic fruit juices, and popsicles as prevention for nausea!

Author: Fred Senese

General Chemistry Online! Antinausea syrup and soda pop have many of the same ingredients- what's the difference?

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