A case study reviewing inhalation devices. The Metered Dose Inhaler (MDI) is the original and most widely used device to deliver inhalation therapies. It uses pressurized gas to release its dose when activated by the patient. More recently, the Dry Powder Inhaler (DPI) has been gaining popularity because it does not rely on propellant to deliver the medication and patients find it convenient and easy to use. Other systems available on the market include liquid droplet inhalers and nebulisers. When developing a new product, researchers can select either a standard inhaler device or decide to develop a customized solution that is more tailored to the requirements of their product and the particular disease area.