> The oral absorption of phenylephrine is erratic. Perhaps that is why it was not used as an oral decongestant until it was the only choice. It had long been kn

> The oral absorption of phenylephrine is erratic. Perhaps that is why it was not used as an oral decongestant until it was the only choice. It had long been known that enzymes in the gut lining metabolized oral phenylephrine to inactive metabolites, reducing the amount of the active compound that could enter the bloodstream. The most cited study found that an oral dose of phenylephrine had an absorption rate of 38 percent of an oral dose of phenylephrine, but this study measured more than just the compound's active form. Later studies with more sensitive tests found that less than 1 percent of oral phenylephrine enters the bloodstream in an active form. Perhaps you have a less active form of the enzyme that degrades it.