How should an adult with acute oral 1,8‑bis‑dimethylamino‑naphthalene (DMAN) poisoning be managed, including decontamination, treatment of methemoglobinemia, hemolysis, and renal injury?

Management of 1,8-Bis-Dimethylamino-Naphthalene (DMAN) Toxicity

Treat DMAN poisoning as a naphthalene-like oxidative toxin causing methemoglobinemia and hemolysis: immediately decontaminate, administer methylene blue 1-2 mg/kg IV for symptomatic methemoglobinemia >20-30%, but absolutely avoid methylene blue if G6PD deficiency is present or suspected, and provide aggressive supportive care with blood transfusions and renal replacement therapy as needed. 1, 2

Immediate Decontamination

• Remove all contaminated clothing and jewelry immediately to prevent ongoing dermal absorption 2
• Irrigate exposed skin with copious running water for at least 15 minutes, as water is effective for most chemical exposures 2
• Decontamination must occur outside the hospital to prevent secondary contamination of healthcare workers 2
• Healthcare personnel should wear butyl rubber gloves and appropriate respiratory protection, as standard surgical masks and latex gloves provide inadequate protection from toxic vapors 2

Assessment of Methemoglobinemia Severity

Check methemoglobin level immediately and correlate with clinical symptoms: 2, 3

• 10-30% MetHb: Cyanosis, headache, tachycardia, mild dyspnea; minimal acidosis 3
• 30-50% MetHb: Clinically significant tissue hypoxia with developing lactic acidosis requiring treatment 3
• >50% MetHb: Profound metabolic acidosis, dysrhythmias, seizures, altered mental status, cardiovascular collapse 3
• >70% MetHb: Potentially lethal with severe high-anion-gap metabolic acidosis 3

Look for the oxygen saturation gap: discordance between pulse oximetry (typically 84-85% despite oxygen) and arterial blood gas oxygen saturation, which is pathognomonic for methemoglobinemia 4, 5

Critical Pre-Treatment Decision: G6PD Status

Before administering methylene blue, strongly consider G6PD deficiency, particularly in high-risk populations (Mediterranean, African, Middle Eastern, Southeast Asian descent). 4, 1

• Methylene blue is absolutely contraindicated in G6PD deficiency because it will not improve methemoglobinemia and will cause severe hemolysis 4, 1, 6
• If G6PD status is unknown and the patient is symptomatic with MetHb >20-30%, the clinical decision must weigh immediate life-threatening methemoglobinemia against potential G6PD-induced hemolysis 2, 1
• If hemolysis is already present alongside methemoglobinemia, strongly suspect G6PD deficiency and avoid methylene blue 4, 7

Treatment of Methemoglobinemia

First-Line: Methylene Blue (if G6PD normal or unknown with life-threatening methemoglobinemia)

Administer methylene blue 1-2 mg/kg IV over 3-5 minutes for symptomatic patients or MetHb >20-30% 2, 3, 8

• Expect methemoglobin levels to fall within 30-60 minutes after administration 2, 3
• Repeat the dose if symptoms do not resolve within 30 minutes 2
• Do not exceed cumulative dose of 7 mg/kg to avoid paradoxical worsening of methemoglobinemia 2, 8
• Provide supplemental oxygen to all patients 2

Alternative Treatment (if G6PD deficiency confirmed or suspected)

Use ascorbic acid (vitamin C) as the primary treatment when methylene blue is contraindicated: 2, 6, 5

• Administer ascorbic acid 0.2-1.0 g/day orally in divided doses, or give IV/IM formulations 2
• Ascorbic acid works more slowly than methylene blue but is safe in G6PD deficiency 2, 6
• Consider adding N-acetylcysteine as adjunctive therapy 5

Rescue Therapies for Refractory Cases

If methylene blue fails or is contraindicated and the patient deteriorates: 2, 3

• Exchange transfusion achieves 81.6% survival rate in methylene blue-refractory cases and directly removes MetHb while supplying functional hemoglobin 2, 3
• Hyperbaric oxygen therapy provides modest additional oxygen delivery despite MetHb presence 2, 3

Management of Hemolysis

Naphthalene-like compounds cause acute intravascular hemolysis 48-96 hours after exposure, presenting with dark brown urine, jaundice, and hemoglobinuria: 1, 5, 9

• Monitor complete blood count, reticulocyte count, indirect bilirubin, LDH, and haptoglobin serially 5, 7
• Provide red blood cell transfusions for symptomatic anemia or hemoglobin <7 g/dL 6, 5
• Hemolysis is more severe in G6PD-deficient patients and may require multiple transfusions 1, 7

Management of Acute Kidney Injury

Acute kidney injury develops from hemoglobin-induced tubular toxicity and requires aggressive intervention: 1, 6

• Maintain aggressive IV hydration to promote hemoglobin clearance and prevent tubular obstruction 6
• Monitor urine output, creatinine, and electrolytes closely 6
• Initiate hemodialysis for KDIGO stage 2-3 acute kidney injury (similar principles to toxic alcohol management) 2, 6
• Continue dialysis until renal function recovers and hemolysis resolves 6

Critical Management Pitfall

Do not delay methylene blue administration to first correct metabolic acidosis—the lactic acidosis resolves only after oxygen delivery is restored by reducing MetHb levels 3

Monitoring Parameters

• Methemoglobin levels every 2-4 hours until <10% 2
• Continuous pulse oximetry and cardiac monitoring 2
• Serial hemoglobin, reticulocyte count, bilirubin, LDH 5, 7
• Renal function (creatinine, urine output) 6
• Arterial blood gas for acid-base status 3