Two decades ago, it became clear that Congress was intent on trying to curtail illicit methamphetamine production by restricting access to pseudoephedrine, a meth precursor that was also widely used as a decongestant in cold and allergy remedies such as Sudafed. Pfizer, the manufacturer of Sudafed products, responded by announcing that it would start selling alternatives containing a different active ingredient: phenylephrine.
What’s the difference between pseudoephedrine and phenylephrine? “SUDAFED products with phenylephrine are available for over-the-counter purchase without restrictions,” explains Johnson & Johnson, which acquired the brand from Pfizer in 2006, while “products that have pseudoephedrine as an active ingredient face restrictions.” Johnson & Johnson does not mention another distinction that might be of interest to consumers: Pseudoephedrine works, while phenylephrine does not. Or so a unanimous panel of experts advised the Food and Drug Administration (FDA) on Tuesday.
The main problem with phenylephrine: When taken orally, it is so thoroughly metabolized in the gut that almost none of it ends up in the bloodstream. “The new data appear compelling that the monographed dosage of oral [phenylephrine] results in no meaningful systemic exposure or evidence of efficacy,” says an FDA briefing document that was presented to the advisory committee. “Furthermore, the review suggests that higher doses…have also not shown efficacy. These findings are supported by in vitro and in vivo clinical pharmacology data showing that orally administered phenylephrine undergoes high first-pass metabolism resulting in less than 1% bioavailability.”
Hellbound and Down 