The extent of flurbiprofen's excretion into mature (postcolostrum) breast milk was evaluated in 10 healthy, nursing mothers after administration of a single 100-mg tablet. Samples of milk and blood were subsequently obtained over a 48-hour period and assayed for flurbiprofen by high-performance liquid chromatography. The average peak plasma flurbiprofen concentration, 15 micrograms/ml, occurred at 1.5 hours, and the harmonic mean half-life of the drug was 5.8 hours. The average peak milk concentration of flurbiprofen was 0.09 microgram/ml, and the maximum recovery of the dose in breast milk was only 0.07%.