Topically applied anesthetic spray is commonly used as part of premedi
cation for general anesthesia and for endoscopic procedures; it is rar
ely associated with side effects. In this report, we describe two case
s of toxic methemoglobinemia that resulted from topically applied anes
thetic spray used before endoscopy. In both cases, standard doses were
used; however, methemoglobin levels of 45 % and 38 % developed within
P hour of the procedure. Both patients had normal levels of erythrocy
te methemoglobin reductase, an indication that this rare but potential
ly fatal side effect can occur in persons who have no predisposing fac
tors. Because toxic methemoglobinemia is easily treated, our report em
phasizes the need to recognize this problem when topically applied ane
sthetic sprays are used.