One of the approaches adopted, as the first treatment method, in previous pandemic viruses before the production of new vaccines or drugs, is to evaluate the effectiveness of existing drugs. Sometimes, it is known that the combination of drugs provides better treatment by increasing the activity of the drugs due to mutual interactions. In this work, we used quantum theory of atoms in molecules and density functional theory to examine the structure and activity relationship between Favipiravir (FPV), a potential antiviral drug for ribonucleic acid viruses, and an inhibitor of influenza virus, and Ibuprofen (IBP), a nonsteroidal anti-inflammatory drug. The drug-likeness evaluations of IBP…FPV were also performed. It was observed that FPV and IBP interact in several ways via hydrogen bonding (HB) leading to changes in the activities of the combined drug and IBP…FPV is predicted to be orally bioavailable. It was also found that the highest occupied molecular orbital (HOMO) is located on IBP and the lowest unoccupied molecular orbital (LUMO) is distributed over FPV. The biological activity of the combined drug system is increased because of the small HOMO-LUMO energy gap value, partially covalent and non-covalent HB interactions.Communicated by Ramaswamy H. Sarma.
Keywords: DFT; Favipiravir; QTAIM; drug interaction; drug-likeness; ibuprofen.