Phenylephrine has been on the U.S. market for 40 years. But it has come into new focus because of a 2006 law restricting sales of pseudoephedrine, a related decongestant. Congress passed a law forcing pharmacies to sell pseudoephedrine from behind the counter because it can be used as an ingredient in manufacturing methamphetamine. Meanwhile phenylephrine remains out on grocery store and pharmacy shelves.
Americans have bought at least 5 billion doses of the drug since 1996, according to a consumer products industry lobbying group. But a group of scientists asked the FDA to review the drug after an analysis suggested the common 10-milligram dose may be ineffective.
Industry groups showed 14 studies to regulators. Half concluded phenylephrine is effective in reducing nasal congestion, but the other half showed no effect. Each of the studies had different designs; some measured congestion by machine in a lab, others asked patients about their symptoms.
Yet the scientists who petitioned the FDA said their analysis of available research shows no benefit to the widely-available 10-milligram oral dose.
"I was really convinced that if you have a stuffy nose and you take 10-milligrams, you're going to still have a stuffy nose," said Leslie Hendeles, a University of Florida professor of pharmacy and pediatrics and one of the scientists who filed the petition.
Hendeles and other scientists had asked the agency to revoke clearance for the 10-milligram dose and instead force companies to study a higher, 25-milligram dose.
In an 11-1 vote, the FDA's advisory panel concluded that available studies suggest 10 milligrams of phenylephrine is effective. But experts also said that existing studies are small and inconclusive, and that companies should conduct more trials.
"The individual studies show some suggestion of a benefit to the 10-milligram [dose]," said Mary E. Tinetti, MD, a professor of medicine at Yale University and the panel's chair.
"Overall what we know from studies to date, is that it's murky," she said.
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