Viagra has been given to PAH patients for years because of its pulmonary vasodilator properties. It might be promising in Covid, but it’s use is controversial among pulmonologists who think more research needs to be done in Covid treatment. In some cases, it can actually lower blood O2 levels by creating a V/Q mismatch, which would not be desirable in a hypoxic Covid patient. Would be great if it shows to be helpful on Covid treatment, though. We need more tools to fight Covid .