Fullerenes have received attentions due to their versatile properties. Molecular structures and electronic properties namely binding energy, band gap, electrophilicity index and molecular topological analysis were studied for undoped and silicon doped C-20 fullerenes and favipiravir in order to search for possible application of the systems as drug delivery vehicles. Density functional theory (DFT) and quantum theory of atoms in molecules (QTAIM) were used for the research. Molecular structures having the interaction edges of SiC19 center dot center dot center dot OH in water and SiC19 center dot center dot center dot O=O in gas phase were found as those most stable with binding energies of -57.28 kcal/mol and -43.46 kcal/mol correspondingly. The results and parameters found in this research may provide additional insights into drug delivery systems.