N-Acetylcysteine Reduces Methemoglobin in an In-vitro Model of Glucose-6-phosphate Dehydrogenase Deficiency |
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Authors: | Robert O. Wright MD Alan D. Woolf MD MPH Michael W. Shannon MD MPH Barbarajean Magnani MD PhD |
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Affiliation: | Harvard University Medical School, Children s Hospital, Boston, MA, Divisions of General Pediatrics;Harvard University Medical School, Children s Hospital, Boston, MA, Divisions of General Pediatrics and Emergency Medicine;Program in Clinical Pharmacology/Toxicology and Departments of Medicine;Laboratory Medicine/Pathology;Brigham and Women's Hospital, Boston, MA, Department of Anesthesia, Center for Experimental Therapeutics and Reperfusion Injury;Massachusetts Poison Control System, Boston, MA;Brown University School of Medicine, Hasbro Children's Hospital/Rhode Island Hospital, Providence, RI, Department of Pediatrics, Division of Emergency Medicine |
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Abstract: | Objective: To determine whether N-acetylcysteine (NAC) reduces methemoglobin (MHB) in an in-vitro model of glucose-6-phosphate dehydrogenase (G6PD) deficiency, given that methylene blue is an ineffective MHB antidote in G6PD deficiency. Methods: Five volunteers donated blood, which was divided equally into 2 test tubes, centrifuged, and washed with Tris-Mopps buffer (pH 7.4, 15 mmol/L glucose). Both tubes were incubated with epiandrosterone (EA) (400 μmol), a specific inhibitor of G6PD. After 75 μL of 0.18 mol hydroxylamine (HA) was added to induce MHB formation, 150 μL of NAC (20 mg/mL) was added to tube 1 and 150 μL of phosphate-buffered saline (PBS) was added to tube 2 as a volume control. Serial MHB levels are reported as a percentage of total hemoglobin (Hb). G6PD activity was measured at baseline, 15 minutes after EA, and at 5 hours. Results: Mean G6PD activity at baseline was 9.2 ± 2.9 U/g Hb (normal >4.6 U/g Hb); 15 minutes after EA was 3.0 ± 1.0 U/g Hb; and at experiment's end was 2.3 ± 0.7 U/g Hb. The mean (±SD) areas under the concentration-time curves (AUCs) of NAC-EA-HA and PBS-EA-HA samples were compared using an unpaired t-test and were significantly different: PBS-EA-HA, 20,400 ± 1,100 % min, vs NAC-EA-HA, 10,400 ± 1,000 % min, respectively (p < 0.05). Conclusion: In this in-vitro model of G6PD deficiency, NAC efficiently reduced MHB. |
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Keywords: | N-acetylcysteine methemoglobin glucose-6-phosphate dehydrogenase deficiency G6PD deficiency toxicology poisoning antidote |
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