Exploratory Investigation of the Limiting Steps of Oral Absorption of Fluconazole and Ketoconazole in Children Using an In Silico Pediatric Absorption Model

Due to the higher total clearance of certain drugs in children than in adults, it is recommended that, in such cases, higher relative doses on a milligram/kilogram basis should be administered to children in order to achieve similar systemic exposure to adults. This is the case for fluconazole and ketoconazole. Even though the lower absorptive surface area and smaller volumes of intestinal fluids in children does not affect fluconazole absorption, cumulative fraction absorbed of ketoconazole seems to be dose dependent. A dose of 200 mg of ketoconazole, which belongs to the class 2a of the Developability Classification System (DCS) in adults, seems to be higher than the maximum absorbable dose in children, and ketoconazole absorption is expected to be solubility limited (i.e., DCS class 2b) in this population, indicating a DCS class migration. Therefore, extrapolating DCS and DCS drug classification from adults to pediatric groups does not seem to be straightforward and the development of specific pediatric classification systems should be a high priority.