The most important selection criterion for dosage forms is the specified route of drug delivery; dry powders, suspensions, and solutions are the preferred dosage forms for inhalation drug products. The selection criteria for an inhalation dosage form for drug delivery to the lungs starts at the preformulation stage.
Factors including the nature of the illness, system of action, age and anticipated condition of the patient are given priority while selecting the inhalation formulations. The choice of an appropriate salt form can be critical, and the preformulation data, such as solubility, hygroscopicity, and stability, may weigh in favor of one dosage form (suspension, solution, or powder) over another.
Preformulation studies are succeeded by late stage discovery, toxicology reports, first-in-human studies, and later stages of human dosing trials, following which they are prepared for commercialization. Ultimately, the inhalation dosage form that provides the optimal drug action is selected over other dosage forms as the end goal of inhalation formulation development is to improve the bioavailability of drugs, increase absorption, and to optimize drug delivery via the inhalation route of administration.