I’m wrote a book about why all knowledge of the truth is fundamentally uncertain. Give it a read!
I’ve also written a lot about AI safety, personal development, and Buddhism, among other things. Most of that’s here on LessWrong, but there’s also some on my blog, Uncertain Updates.
Whenever I see claims about this, I always want to push back, because phenylephrine works quite well for me. Depending on how congested I am I might have to go slightly above the recommended dosing schedule, but usually I can take the amount recommended or less and it will keep my sinuses clear.
I understand it doesn’t work for everyone, so it makes me suspicious that the studies may be seeing issues like RCTs on SSRIs do, where the drugs work, but which drug works for which person is highly variable, so they seem ineffective in an RCT but seem highly effective in practice once the patient-drug matching process is done.