Increased Phenylephrine Plasma Levels with Administration of Acetaminophen

New data suggest that use of acetaminophen with phenylephrine results in twice the expected plasma levels of phenylephrine. Not all assumptions about over-the-counter drug combinations have been tested. To the Editor: Over-the-counter combinations containing acetaminophen and phenylephrine for the treatment of the common cold and influenza are widespread after the substitution of phenylephrine for pseudoephedrine. This substitution has been allowed in the United States and elsewhere without any additional safety or efficacy studies, since phenylephrine has been called “generally recognized as safe and effective” at oral doses of 10 mg on the assumption that the pharmacokinetic behavior of one drug is not altered by another, despite a lack of supporting data. 1 – 3 Three randomized, open-label, crossover studies in healthy volunteers were undertaken as part of the development of . . .