The Occurrence of Methemoglobinemia during Sulfanilamide Therapy.

The presence of methemoglobin, more rarely sulfhemoglobin, in the blood of patients treated with sulfanilamide has been reported by many investigators (1 a-f). Evelyn and Malloy (2), using their photoelectric colorimeter, found both these pigments but felt they were not responsible for the " cyanosis." Wendel (3), using his visual spectroscopic method (4), found methemoglobin and (occasionally) sulfhemoglobin. On the other hand, Marshall (5), Posner (6a) in many instances, Chesley (6b), and some occasional observers have failed to find the characteristic band of methemoglobin. A little spectroscopic experimentation with pure methemoglobin will speedily convince anyone that the light absorption characteristics of methemoglobin renders visual detection of the band at 630m, rather difficult in the presence of a large excess of hemoglobin. Even Wendel's ingenious method (4) does not eliminate the difficulty of finding this band. If the personal visual factor might be eliminated, incontrovertible evidence might be obtained. This is possible with the Hardy recording spectrophotometer (7) which accurately draws a curve showing the light transmission of a sample from 400 to 700mu. Typical curves of the blood of patients receiving sulfanilamnide are reproduced (Figure 1) with normal controls. The prominent depression at 630 mp is readily seen. In one case a depression at 620 m,u is also seen indicating the presence of sulfhemoglobin. In these patients from 10 to 18 per cent methemoglobin was estimated to be present by using Beer's and Bouguer's laws and absorption coefficients obtained on pure solutions by the Hardy recording spectrophotometer (Table I). Inasmuch as sulfanilamide in vitro does not produce methemoglobin, the mechanism of its formation in vivo remains unexplained. Further ex1 Moritz Rosenthal Fellow, Mount Sinai Hospital, New York City. TABLE I