The Drug-Induced Respiratory Disease Website and App

XIV.a

XIV - Hemoglobinopathies - Abnormal hemoglobin states (acquired)

Methemoglobinemia

Last update 16/10/2014

See also under XIVa. Known since the 1940s (PMID 18883450). Comprehensive list of causal drugs and chemicals available at PMID 1564446. Methemoglobin is the oxidized (Fe3+) species of hemoglobin (Fe2+). Patients present with slate-grey cyanosis, low SpO2, normal SaO2 and PaO2. Normally, methemoglobin is <1%. Levels above 40% can be life-threatening, producing pulmonary edema, cardiovascular collapse (PMID 17122537) CNS disturbances and death. Management includes i.v. methylene blue. A possible rebound increase in MeHb upon treatment requires close monitoring. Excess methylene blue can also produce methemoglobinemia

Causative drugs

Frequency - Incidence

Incidence of respiratory adverse event(s) due to the specific drug as assessed by number of reported/published cases in the literature. Red digits in stars indicate: 0 = Very rare, questionable signal · 1 = < 10 cases · 2 = 10-50 cases · 3 = 50–100 cases · 4 = 100-200 cases · 5 = >200 cases

Evidence level/grade

Evidence level for respiratory adverse event(s) due to the specific drug as estimated using Hill’s (1965), Naranjo’s (1981), and Bégaud’s (1985) criteria applied to published cases. Blue digits in stars indicate: 0 = Questionable · 1 = Low · 2 = Moderate · 3 = Robust · 4 = Definite · 5 = Unquestionable, pathognomonic