Metered dose inhalers (pMDIs), dry powder inhalers (DPIs), and nebulized solutions and suspensions each have relative advantages, disadvantages, and challenges.  For example, the dosage forms differ in their availability of off-the-shelf devices, they can accommodate different dose ranges, and they have markedly different types of formulations.  The latter means that, where possible, selection of a drug form (e.g. salt form if applicable) should be considered in tandem with selection of the dosage form, as the physicochemical properties of the drug may play a leading role in dosage form feasibility. Other factors for consideration include the target patient population, biopharmaceutics, physic-chemical characteristic of the active (API), intellectual property, marketing, competitive landscape, and timeline and budget for the development program.