Phenylephrine is primarily used as a decongestant, vasopressor, and mydriatic agent. It has poor oral bioavailability (~38%) due to extensive first-pass metabolism. The FDA has questioned its efficacy as an oral decongestant, with studies showing it performs no better than placebo at standard 10 mg doses. It is significantly less effective than pseudoephedrine but remains available over-the-counter because it cannot be used to synthesize methamphetamine. Phenylephrine does not cross the blood-brain barrier and has no central psychoactive effects.
Phenylephrine molecular structure diagram from the DrugsPRO substance library.
Also known as: Mesaton, Mezaton, Mydfrin, Isophrin, Visadron, Neo-Synephrine, Vazculep, Sudafed PE
Heavy: Prolonged daily use >3–5 days (avoid; rebound risk) %
Light: 0.125–0.25% %
Common: 0.25–1% (short‑term use) %
Strong: 1% (short‑term use only) %
Threshold: 0.125% %
Duration
Onset: 0.08-0.17 h
Peak: 0.25-0.5 h
Offset: 1-3 h
After Effects: 0 h
Total Duration: 2-4 h
Harm Reduction
Check interactions before mixing substances, pay attention to dose spacing and hydration, and treat all dosage guidance as approximate rather than guaranteed safe.
Sources
Substance data is aggregated from the following public harm-reduction and reference sources.
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Phenylephrine - DrugsPRO substance guide
Phenylephrine: Phenylephrine is primarily used as a decongestant, vasopressor, and mydriatic agent. It has poor oral bioavailability (~38%) due to extensive first-pass metabolism. The FDA has questioned its efficacy as an oral decongestant, with studies showing it performs no better than placebo at
