Mouth washing after inhalation of corticosteroids is eŠective for prevention of local adverse eŠects. We determined the amounts of drug residues remaining on the oropharyngeal mucosa following inhalation of budesonide (BUD) via a Turbuhaler (BUD-TH) (100 mg). Further, we studied the eŠects of mouth washing on the removal of drug residues by quantiˆcation of BUD in expectorated wash solution using an HPLC method. The amount of BUD recovered after gargling and rinsing for 5 s each was 19.4±9.4 mg, as compared to 23.8±13.6 mg after rinsing alone for 10 s and 18.3±8.9 mg after gargling alone for 10 s, though the diŠerences were not signiˆcant. Our results indicated that about 20% of the dose was remaining on the oropharyngeal mucosa after inhalation. In a comparison of washing times, the amounts of BUD recovered were 26.3±3.2 mg after gargling and rinsing for 3 s each, and 19.4±9.3 mg after those for 5 s each. As for the eŠect of lag time before beginning mouth washing, the ratio of BUD recovered following mouth washing with a lag time of 1 min was 73.2%, while it was reduced to 27.8% after 10 min, as compared to immediate mouth washing following administration. Our results suggest that the amount of BUD removed by mouth washing is associated with the lag time between inhalation and mouth washing, however, not with the duration of mouth washing. We concluded that immediate mouth washing after inhalation is most useful for the removal of drugs following BUD-TH administration.