The aim of this study was to establish an appropriate inhalation method with a mometasone furoate dry powder inhaler (MF-DPI). Utilizing a tone-based inhalation training device, we investigated the maximum peak inspiratory flow rate time (T max PIFR) and peak inspiratory flow rate (PIFR) to determine whether either had an influence on lung deposition with use of an MF-DPI. A low tone indicated a PIFR of 28 L/min and a high tone that of 40 L/min, while 60 L/min was considered to be the standard. We established an inhalation profile in consideration of a human inhalation pattern, in which T max PIFR was set at 0.5 s (T max PIFR 0.5 s) and 2.5 s (T max PIFR 2.5 s). The reference cut-off value derived with a cascade impactor test was used for evaluation of the rate of delivered dose in the lung, which was the amount of drug from stage 3 to 7 at all PIFRs. We then investigated the relationship of the fine particle fraction (FPF) with the claimed dose at T max PIFR of 0.5 s and PIFR. There were no differences among the T max PIFR values for the doses emitted from the device or for the rate of delivered doses in stages 3-7. However, FPF for the claimed dose at 40 L/min was significantly lower than that at 60 L/min, which was dependent on PIFR. Our results showed that PIFR but not T max PIFR has an effect on lung deposition after inhalation with an MF-DPI.Key words mometasone furoate; dry powder inhaler; maximum peak inspiratory flow rate time; peak inspiratory flow rate; lung deposition A mometasone furoate dry powder inhaler (MF-DPI) is a device utilized for administration of inhaled corticosteroid, which is used for treatment of asthma. MF binds with high affinity to the corticosteroid receptor and has anti-inflammatory potency, [1][2][3] and is formulated for delivery via a breath-actuated DPI using a Twisthaler ® . Doses emitted from the device have been shown to be high, with flow rates ranging from 28.3 to 70 L/min. 4) That study also revealed that the dose emitted from the device has a relationship with flow rate, 4) though the relationship between dose and lung deposition amount is not clear. Furthermore, the mass median aerodynamic diameter (MMAD) of an MF-DPI is 2.0 µm, the smallest among available, thus it is characterized by the design of the particles used, which reach from the central to small airway. An inhalation training device (manufactured by Taisei Kako Co., Ltd.) that emits tones and is used in a manner similar to an MF-DPI has been produced to practice inhalation. This device produces a low tone at a peak inspiratory flow rate (PIFR) of 28 L/ min and a high tone at that of 40 L/min. However, the relationship between PIFR-produced tones and the dose delivered to the lung has not been examined.The rate of drug deposition in the lung has been examined in vitro in inhalation experiments. Those results revealed that PIFR actually sensed by patients was not reflected in those experimental results, as resistance to inhalation was not included in measured PIFR. In addition, individualized inhalation profi...