Phenylephrine is a selective a₁-adrenergic receptor agonist of the phenethylamine class used primarily as a decongestant, as an agent to dilate the pupil, and to increase blood pressure. Phenylephrine is marketed as an alternative for the decongestant pseudoephedrine, though clinical studies show phenylephrine to be no more effective than placebo. Phenylephrine can also cause a decrease in heart rate through reflex bradycardia.