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VARIOUS › DIAGNOSTIC AGENTS › OTHER DIAGNOSTIC AGENTS › Tests for gastric secretion
methylthioninium chloride
V04CG05
Forms & Strengths
- Intravenous injection: 10 mg/mL in 10 mL ampoules
Adult Dosing
- Acquired methemoglobinemia: 1 to 2 mg/kg (0.1 to 0.2 mL/kg) administered intravenously slowly over several minutes
- Repeat dose: If methemoglobin levels remain elevated or clinical signs persist, a repeat dose of up to 1 mg/kg may be given after 1 hour
- Maximum cumulative dose: 7 mg/kg
Pediatric Dosing
- Acquired methemoglobinemia (infants > 3 months and children): 1 to 2 mg/kg (0.1 to 0.2 mL/kg) IV slowly over several minutes
- Repeat dose: May repeat 1 to 2 mg/kg once after 1 hour if necessary
- Neonates: Generally avoided or used with extreme caution at lower doses (0.3 to 0.5 mg/kg) due to prolonged elimination half-life
Indications
- Treatment of acute symptomatic acquired methemoglobinemia
- Visualization of tissues and fistulas during diagnostic procedures (off-label/alternative uses)
Mechanism of Action
- Acts as an electron acceptor in low concentrations, where reduced nicotinamide adenine dinucleotide phosphate (NADPH) methemoglobin reductase reduces methylene blue to leukomethylene blue
- Leukomethylene blue then non-enzymatically reduces methemoglobin back to functional hemoglobin
Contraindications
- Severe renal impairment (creatinine clearance < 30 mL/min)
- Glucose-6-phosphate dehydrogenase (G6PD) deficiency due to risk of hemolysis
- Known hypersensitivity to methylene blue or thiazine dyes
- Methemoglobinemia induced by nitrite poisoning during cyanide poisoning treatment
- Intrathecal administration
Adverse Reactions
- Cardiovascular: Hypertension, hypotension, chest pain, arrhythmias
- Central nervous system: Confusion, dizziness, headache, fever, mental confusion
- Gastrointestinal: Nausea, vomiting, abdominal pain, diarrhea
- Hematological: Hemolytic anemia (especially in G6PD deficiency), methemoglobinemia (at high doses)
- Dermatological: Blue-green discoloration of urine, skin, and mucous membranes
- Respiratory: Dyspnea, tachypnea, hypoxia
Drug Interactions
- Serotonergic agents (SSRIs, SNRIs, MAOIs, TCAs): Risk of severe central nervous system toxicity, serotonin syndrome
- CYP1A2 substrates: Potential for altered metabolism
- Drugs causing hemolysis: Additive risk of hemolytic anemia in susceptible patients
Curated Content: Needs Vetting Before Put to Clinical Use