The following is a scientific presentation by Colonel Bruno Pradines (Institut de Recherche Biomédicales des Armées, Service de Santé des Armées, VITROME, IHU) which shows the anti-viral properties of old school drugs: chloroquine, hydroxychloroquine, ivermectin and doxycycline.
Patients (i.e. dermatology patients taking doxycycline for rosacea or other skin conditions) or populations where malaria is prevalent and are taking these drugs, didn't get COVID-19 or were hardly affected.
He explains that methylene blue can reach anti-malarial equivalents as artemisinin (anti-malarial herb). So he poses the question if methylene blue is a valid treatment in COVID. And the answer seems to be a definite yes. It has an anti-viral effect:
Colonel Bruno talks about methylene blue at the usual prescribed doses on the last slide.
Caveat lector: Using methylene blue has its indications on specific diseases, and it has its side effects. You can read a dedicated thread here:
First, this post will briefly explain the process of cellular respiration. Then it will highlight the importance of proper mitochondrial function (bioenergetics) for maintaining the health of the organism, and will further show how poor mitochondrial function/energy production is an essential...
cassiopaea.org
So context is everything. Just keep in mind that it has specific anti-viral properties.
He proposes combining the above drugs in case of COVID to use lower doses. For instance, methylene blue and doxycycline. Ivermectin and HCQ and so forth.
Notice that these drugs are old school medicines, and they have a track record of efficacy and safety. You would be surprised to learn that HCQ is safer to use than methylene blue.