Methylene blue (methylthionine chloride U. S. P.) has recently been much in the lay press, not only as an antidote for cyanide, which it is, but also for carbon monoxide, which it is not.
P. J. Hanzlik1 has reviewed the evidence that this substance is an antidote to cyanide. As he points out, the antagonistic property of methylene blue for cyanide was demonstrated experimentally as early as 1926 and has been confirmed by more recent work.
On the other hand, the alleged antagonism between methylene blue and carbon monoxide has no valid support. The theoretical basis of the claim for an antidotal action is derived from the brilliant investigations of Warburg;2 but Warburg's observations on isolated tissues have no real bearing on carbon monoxide asphyxia in man. The experiments of Matilda M. Brooks3 on animals are of little evidential value. The fact is that in its effect
HAGGARD HW, GREENBERG LA. METHYLENE BLUE: A SYNERGIST, NOT AN ANTIDOTE, FOR CARBON MONOXIDE. JAMA. 1933;100(25):2001-2003. doi:10.1001/jama.1933.02740250023006