Background: Methylene blue is an ineffective methemoglobin (MHB) antidote in glucose-6-phosphate dehydrogenase (G6PD) deficiency. We previously reported that N-acetylcysteine (NAC) will reduce MHB in normal blood. Objective: To determine if NAC will reduce MHB in an in vitro model of G6PD deficiency. Methods: Five volunteers donated blood, which was divided equally into 2 tubes, centrifuged, washed and resuspended with Tris-Mops buffer (pH 7.4, 15 mM glucose). Both tubes were incubated with epiandrosterone (EA) (400μM) a specific inhibitor of G6PD, then with hydroxylamine (6mM) to induce MHB formation. 150 μl of NAC (20 mg/ml) was added to the experimental tube, and 150 μl of phosphate buffered saline (PBS) added to the control tube. G6PD activity was measured at baseline, 15 minutes after EA and at 5 hours. Serial MHB levels are presented as a percent of toal hemoglobin. Results: Baseline G6PD activity was 9.2±2.9 U/gHgb (mean ± SD) (normal >4.6 U/gHgb); 3.0±1.0 U/gHgb 15 minutes after EA; and 2.3±0.7 U/gHgb at 5 hours. Table Difference in areas under time-concentration curves were significant (p < 0.05). Conclusion: In this in vitro model of G6PD deficiency, NAC reduced MHB. NAC may be an alternative antidote for patients with G6PD deficiency suffering from MHB.

Table 1
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