The quality of evidence is upgraded by very large magnitude of effect.
There are no randomized controlled trials (Cochrane review «Adrenaline (epinephrine) for the treatment of anaphylaxis with and without shock»1 «Sheikh A, Shehata YA, Brown SG, Simons FE. Adrenal...»1) comparing adrenaline with no intervention, placebo or other adrenergic agonists in the treatment of anaphylaxis. Several observational studies and case series show a rapid and often dramatic effect of adrenaline, and a better prognosis for patients who receive adrenaline early compared to those who receive no or delayed adrenaline.