dry-powder inhaler (DPI)

A dry-powder inhaler delivers medicine as a tiny cloud of fine powder rather than a wet spray, and crucially it is powered by your own breath: when you inhale sharply, the rush of air sweeps the powder out, breaks up clumps, and carries the drug into the lungs. There is no propellant and usually no press-and-breathe timing to coordinate.

The drug is micronized to a few micrometres so it can reach the deep airways, but such fine powder is sticky and flows badly, so it is usually blended with larger carrier particles (often lactose) that it loosely clings to. As you breathe in, turbulence and the device's flow path strip the drug from the carrier — a process called deaggregation — letting the small drug particles fly on into the lung while the heavy carrier mostly drops out in the mouth and throat.

Because delivery depends on inspiratory effort, a patient who cannot inhale forcefully enough (a young child, or someone in a severe asthma attack) may not disperse the powder properly and get too little drug. DPIs avoid propellants and coordination problems and are often easy to use, but they are sensitive to humidity (powder can clump) and to how hard the patient inhales, so device resistance and instruction matter.