The complex physiology and anatomy of the lungs and the range of processes involved in pulmonary drug transport and disposition make it challenging to predict the fate of orally inhaled drugs. This study aimed to develop an integrated computational pharmacology approach to mechanistically describe the spatio-temporal dynamics of inhaled drugs in both systemic circulation and site-specific lung tissue. The model included all the physiologically relevant pulmonary processes, such as deposition, dissolution, transport across lung barriers, and mucociliary clearance, to predict the inhaled drug pharmacokinetics. For validation test cases, the model predicted the fate of orally inhaled budesonide (highly soluble, mildly lipophilic) and fluticasone propionate (practically insoluble, highly lipophilic) in healthy subjects for: i) systemic and site-specific lung retention profiles, ii) aerodynamic particle size-dependent deposition profiles, and iii) identified the most impactful drug-specific, formulation-specific, and system-specific property factors that impact the fate of both the pulmonary and systemic concentration of the drugs. In summary, the presented multiscale computational model can guide the design of orally inhaled drug products to target specific lung areas, identify the effects of product differences on lung and systemic pharmacokinetics, and be used to better understand bioequivalence of generic orally inhaled drug products.