Only three drugs are commonly used as oral decongestants: phenylpropanolamine (PPA), pseudoephedrine (PDE), and phenylephrine (PE). They are all chiral drugs that exist as stereoisomers. It is possible that each enantiomer can reflect significant enantioselective differences with regard to both pharmacokinetic and pharmacodynamic effects. Both PPA and PDE are readily and completely absorbed, whereas PE, with a bioavailability of only approximately 38%, is subject to gut wall metabolism and is thought to be absorbed erratically. Peak concn are reached between 0.5 and 2 hr after admin. All three drugs are extensively distributed into extravascular sites (apparent volume of distribution between 2.6 and 5.0 L/kg). No protein binding data in humans are available. Whereas PPA and PDE are not substantially metabolized, PE undergoes extensive biotransformation in the gut wall and the liver. Elimination of PPA and PDE is predominantly renal, with urinary excretion being pH dependent. Half-lives are relatively short, approximately 2.5 hr for PE, 4 hr for PPA, and 6 hr for PDE. Elimination of PPA and PDE may be rapid in children, and the agents should be used with caution in patients with renal impairment. In addition, PPA incr caffeine plasma levels and decr theophylline clearance. Reduced metabolism of PE occurs with concurrent admin of monoamine oxidase inhibitors. No direct relationship between nasal decongestant effect and plasma concentration has been established.