Naproxen belongs to the class of non-steroidal anti-inflammatory drugs (NSAIDs) and as such is used to treat mild to moderate pain, fever, inflammation and arthralgia in certain chronic conditions. This class of anti-inflammatory drugs has an effect on inflammation and pain by inhibiting an important enzyme in these mechanisms, cyclo-oxygenase (COX). There are several cyclo-oxygenases and naproxen is not specific to any one, unlike the newer NSAIDs that specifically target the COX-2 protein.

Although NSAIDs are strongly discouraged during a viral infection because their action inhibits certain mechanisms of innate immunity, ongoing studies with Covid-19 are investigating the effect of NSAIDs on the "cytokine storm" phenomenon observed in the most severe cases. The symptoms of respiratory distress observed with Covid-19 caused by VCOS-COV-2 SARS can be reduced by drugs that combine anti-inflammatory and antiviral effects. This dual effect can simultaneously protect critically ill patients and reduce viral load, thereby limiting the spread of the virus.