The proverb "Old is gold" is applicable in drug discovery and the proverb "All 
that Glitters is not Gold" is also appropriate. In the COVID-19 era, there has 
been a race for drugs to be effective against SARS-CoV-2. There are reports 
about the uses of Remdesivir and Favipiravir as existing antivirals against 
virus but none have been conclusive so far. In the attempts for innovations, the 
combination of drugs is also under trials. Therefore, we used the density 
functional theory method and quantum theory of atoms in molecules to investigate 
drug-drug interactions involving Remdesivir and Favipiravir. The computed 
parameters were related to the antiviral actions of both drugs together. The 
results indicate enhanced antiviral activity and it will be worthy to consider 
additional investigations with the combination of these two drugs.