Methylene blue is used for the treatment of drug-induced methemoglobinemia. Methylene blue has been used for methemoglobinemia associated with certain drugs (e.g., dapsone, benzocaine, lidocaine), occupational or other exposures to toxic chemicals (e.g., hydrazine, aniline and other amine-substituted benzenes, chloronitrobenzene and other nitro-substituted benzenes, nitrates, nitrites), or substance abuse (e.g., inhalation or ingestion of volatile nitrites).
Methylene blue will not reverse methemoglobinemia in patients with glucose-6-phosphate dehydrogenase (G-6-PD) deficiency, and may induce or exacerbate hemolysis in these patients.
(See Cautions: Adverse Effects.)
Methylene blue has been used for the treatment of cyanosis in patients with congenital methemoglobinemia related to cytochrome b5 reductase deficiency, but is ineffective in patients with hemoglobin M (abnormal hemoglobin molecules).
Methylene blue is not effective for the treatment of sulfhemoglobinemia.
Methylene blue has been used in the management of ifosfamide-induced encephalopathy. Although methylene blue has resulted in rapid improvement in CNS function in some patients, beneficial effects have not been consistently reported and further clinical studies are needed to establish the role of the drug in the management of ifosfamide-induced encephalopathy. Methylene blue does not appear to be effective when used prophylactically in an attempt to prevent ifosfamide-associated encephalopathy.
Use as a Dye
Methylene blue is used as a bacteriologic stain, as an indicator dye, and for surgical and medical marking.
Methylene blue has been administered by local injection or instillation as a diagnostic (visualizing) dye in a variety of procedures, including sentinel lymph node biopsy in cancer patients (e.g., breast cancer patients), endoscopic evaluation of lesions in patients with gastroesophageal reflux disease (GERD) or Barrett's esophagus, urologic evaluation in patients with ureteral or renal pelvis injury, and thoroscopic procedures in patients with pulmonary nodules.
Although further study is needed to evaluate safety and efficacy, methylene blue has been used topically as a photosensitizer for photodynamic therapy (PDT) in the topical treatment of dermatologic or mucocutaneous infections (e.g., herpes labialis, eczema herpeticum, oral candidiasis, cutaneous leishmaniasis, chromoblastomycosis) or chronic dermatologic or mucocutaneous conditions (e.g., plaque psoriasis, oral lichen planus).
Cyanide and Carbon Monoxide Poisoning
Although methylene blue was used in the past as an antidote for cyanide poisoning, it is no longer recommended for this use. Cyanide poisoning usually is treated with an antidote regimen consisting of amyl nitrite, sodium nitrite, and sodium thiosulfate or with hydroxocobalamin. When sodium nitrite is used for cyanide poisoning, methylene blue should not be used in an attempt to treat excessive methemoglobinemia induced by the antidote because reduced cyanide binding and increased toxicity occurs.
Methylene blue is of no value in the treatment of carbon monoxide poisoning.
Cystitis and Urethritis
Methylene blue was used in the past as a mild urinary antiseptic and stimulant to mucous surfaces in the treatment of cystitis and urethritis, but is no longer recommended for this use.
Methylene blue has been used alone and in combination with ascorbic acid for the management of chronic urolithiasis. Although methylene blue appears to have some inhibitory effect on the formation of calcium oxalate and calcium phosphate crystals in some patients, the drug is not currently recommended for this use and is ineffective in dissolving previously formed stones.