An improved inhalation device is provided for facilitating inhalation by a patient of powder medicaments contained in a receptacle. The inhalation device includes a staple assembly comprising a plunger and staple that are securely and robustly coupled to one another. Embodiments of the inhalation device have a cap that prevents or reduces the amount of dust and grime entering into the device. The cap is additionally configured to prevent or reduce inadvertent and unintentional operation of the device. The body portion and first casing portion of certain embodiments of the inhalation device are sealably coupled, restricting or reducing undesirable flow pathways that have an adverse effect on the operation of the device.