Oral phenylephrine is essentially worthless as a decongestant.

• Thanks to the meth wars, cold medicine’s effective ingredient isn’t • 2015 Oct 30 • Cory Doctorow • boingboing
• Oral Phenylephrine HCl for Nasal Congestion in Seasonal Allergic Rhinitis: A Randomized, Open-label, Placebo-controlled Study • 2015 Sep-Oct • Meltzer et al • The Journal of Allergy and Clinical Immunology: In Practice
• The Popular Over-The-Counter Cold Medicine That Science Says Doesn’t Work • 2015 Oct 26 • David DiSalvo • Forbes

Intranasal phenylephrine probably works better (although you run into the issue of rebound congestion and rhinitis medicamentosa.

And IV phenylephrine will definitely cause systemic vasoconstriction, presumably including the arterioles in the nasal mucosa, but this is definitely not standard of care for the treatment of nasal congestion (plus you might stroke out or have an MI.)

Your best bet is to get some pseudoepherine from the pharmacist. I know civil libertarian types are skittish of having to present ID, but if you’re in the drug store, you’re already on surveillance camera anyway. I mean, if you really don’t want to present ID or be recorded on camera, you could always just go to your local meth dealer #NotMedicalAdvice