The standard 10mg dose is too low. Decongestants work by constricting blood vessels, which inherently increases blood pressure as a side effect.
Pseudoephedrine at standard doses is known to raise blood pressure slightly. Phenylephrine at standard doses (10mg) shows no such effect (Source https://journals.lww.com/ebp/abstract/2018/03000/how_much_do... )
Phenylephrine does increase blood pressure when delivered by IV at doses that work. The oral 10mg dose just isn't enough to get absorbed and do anything.
It's not that phenylephrine is ineffective, it's that it's underdosed in the oral formulation.
[0] https://superuser.com/questions/1221333/screensharing-under-...
This is still very impressive for a computer program, but not as mind-blowing as I first thought when reading the thread. ChatGPT didn't find some obscure disease like in a medical TV show. Rather, it correctly read the low blood cell count, and pulled up the differentials for anemia from a reference book.
On a side note, considering how often ChatGPT will lie with full confidence, personally I can't imagine using it for anything medically related.