Methylene Blue

Drug-induced methemoglobinemia

Methylene blue can cause fetal harm when administered to a pregnant woman. An association exists between the use of methylene blue in amniocentesis and atresia of the ileum and jejunum, ileal occlusions, and other adverse effects in the neonate. (2, 3) Methylene blue is contraindicated in women who are or may become pregnant. If this drug is used during pregnancy, or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential hazard to the fetus.

Intraspinal and subcutaneous injections are contraindicated. Methylene blue is contraindicated in patients with a known hypersensitivity to the drug.

Methylene blue should not be given by subcutaneous or intrathecal injection. Methylene blue is a potent monoamine oxidase inhibitor: Methylene blue has been demonstrated to be a potent monoamine oxidase inhibitor (MAOI) and may cause potentially fatal serotonin toxicity (serotonin syndrome) when combined with serotonin reuptake inhibitors (SRIs). (4) (see DRUG INTERACTIONS .) Serotonin toxicity is characterized by development of neuromuscular hyperactivity (tremor, clonus, myoclonus, and hyperreflexia, and, in the advanced stage, pyramidal rigidity); autonomic hyperactivity (diaphoresis, fever, tachycardia, tachypnoea, and mydriasis); and altered mental status (agitation, excitement, and in the advanced stage, confusion).

If methylene blue is judged to be indicated, SRIs must be ceased, prior to treatment/procedure/surgery.