Fig. 1.

Compartment model for characterization of plasma concentration after administration of ICS. F _Lung fraction of the emitted dose that is deposited in the lung, F _Mouth fraction of the emitted dose that is deposited in the oropharynx, F _C fraction of the lung dose that is deposited in central regions of the lung (LC₁), F _P fraction of the lung dose that is deposited in peripheral regions of the lung (LP₁), LC ₂ compartment representing central lung regions where the drug is dissolved, LP ₂ compartment representing peripheral lung regions where the drug is dissolved, F _BA oral bioavailability, k _muc mucociliary clearance, k _a drug absorption from the gut into the systemic absorption, k _diss dissolution of drug particles, k _pul,C drug absorption from central lung regions into the systemic circulation (central body compartment), k _pul,P drug absorption from peripheral lung regions into the systemic circulation, k ₁₂ and k ₂₁ drug distribution between central and peripheral body compartments; k ₁₀ drug elimination from the systemic circulation. All rate constants (k) were assumed to be first-order processes