The drug is called tadalafil, and it's used in the generic form of Cialis.
The chemicals, worth $179,000, were seized last week.
Authorities said they stopped a 40-year-old Korean man after an inspection found sealed pouches of a white powdery substance in his carry-on bags.
He claimed it was a Chinese herb, but lab tests determined it was tadalafil.
The Associated Press contributed to this report.