Important: This page is general information, not medical advice. It does not recommend or prescribe any treatment. Always consult your doctor or pharmacist before starting, stopping or changing any medicine.
Quick facts
- How it is given
- intravenous
- Type
- human prescription drug
- RxNorm ID
- 1788984
We do not publish dosing. How much of this medicine to take, how often, and for how long depends on your age, weight, kidney and liver function, other conditions and other medicines. That is a decision for the person who prescribes or dispenses it. Follow the directions on your own pack and ask your pharmacist if anything is unclear.
What it is used to treat
Methylene Blue Injection is indicated for the treatment of pediatric and adult patients with acquired methemoglobinemia. Methylene Blue Injection is an oxidation-reduction agent indicated for the treatment of pediatric and adult patients with acquired methemoglobinemia.
About this medicine
Methylene blue is an oxidation-reduction agent. Its chemical name is 3,7-bis(dimethylamino)phenothiazin-5-ium, chloride hydrate. The molecular formula of methylene blue is C 16 H 18 ClN 3 S•xH 2 O and its molecular weight of 319.85 g/mol for the anhydrous form. The structural formula of methylene blue is: Methylene Blue Injection, USP is a sterile solution intended for intravenous administration. Each mL of solution contains 5 mg methylene blue, USP and water for injection, USP. Methylene Blue Injection, USP is a clear dark blue solution with a pH value between 3.0 and 4.5. The osmolality is between 10 and 15 mOsm/kg. Methylene Blue Injection, USP strength is expressed in terms of trihydrate. Structural Formula
How it works
12.1 Mechanism of Action Methylene blue is a water soluble thiazine dye that promotes a non-enzymatic redox conversion of metHb to hemoglobin. In situ, methylene blue is first converted to leucomethylene blue (LMB) via NADPH reductase. It is the LMB molecule which then reduces the ferric iron of metHb to the ferrous state of normal hemoglobin.
Who should not take it
Methylene blue injection is contraindicated in the following conditions: Severe hypersensitivity reactions to methylene blue or any other thiazine dye [see Warnings and Precautions (5.2) ] . Patients with glucose-6-phosphate dehydrogenase deficiency (G6PD) due to the risk of hemolytic anemia [see Warnings and Precautions (5.3 , 5.4 )] . Methylene blue injection is contraindicated in the following conditions ( 4 ): Severe hypersensitivity to methylene blue Patients with glucose-6-phosphate dehydrogenase deficiency (G6PD) due to the risk of hemolytic anemia
Warnings and cautions
Hypersensitivity: If severe or life threatening allergic reaction occurs, discontinue methylene blue injection, treat the allergic reaction, and monitor until signs and symptoms resolve. ( 5.2 ) Lack of Effectiveness: Consider alternative treatments if there is no resolution of methemoglobinemia after 2 doses. ( 2.1 , 5.3 ) Hemolytic Anemia: Discontinue methylene blue injection and transfuse. ( 5.4 ) Interference with In Vivo Monitoring Devices: Use methods other than pulse oximetry to assess oxygen saturation. ( 5.5 ) Effects on Ability to Drive and Operate Machinery: Advise patients to refrain from these activities until neurologic and visual symptoms have resolved. ( 5.6 ) 5.1 Serotonin Syndrome with Concomitant Use of Serotonergic Drugs and Opioids The development of serotonin syndrome has been reported with the use of methylene blue class products. Most reports have been associated with concomitant use of serotonergic drugs (e.g., selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), monoamine oxidase inhibitors (MAOIs)). Opioids and dextromethorphan may increase the risk of developing serotonin syndrome. Some of the reported cases were fatal. Symptoms associated with serotonin syndrome may include the following combination of signs and symptoms: mental status changes (e.g., agitation, hallucinations, delirium, and coma), autonomic instability (e.g., tachycardia, labile blood pressure, dizziness, diaphoresis, flushing, and hyperthermia), neuromuscular symptoms (e.g., tremor, rigidity, myoclonus, hyperreflexia, and incoordination), seizures, and/or gastrointestinal symptoms (e.g., nausea, vomiting, diarrhea). Avoid concomitant use of methylene blue injection with serotonergic drugs and opioids. Patients treated with methylene blue injection should be monitored for the emergence of serotonin syndrome. If symptoms of serotonin syndrome occur, discontinue use of methylene blue injection, and initiate supportive treatment. […]
Reported side effects
The following adverse reactions are discussed in greater detail in other sections of the labeling: Serotonin Syndrome with Concomitant Use of Serotonergic Drugs [see Warnings and Precautions (5.1) ] Anaphylaxis [see Warnings and Precautions (5.2) ] Lack of Effectiveness [see Warnings and Precautions (5.3) ] Hemolytic Anemia [see Warnings and Precautions (5.4) ] Interference with In Vivo Monitoring Devices [see Warnings and Precautions (5.5) ] Effects on Ability to Drive and Operate Machinery [see Warnings and Precautions (5.6) ] Interference with Laboratory Tests [see Warnings and Precautions (5.7) ] The most commonly reported adverse reactions (≥2%) included headache, hypokalemia, diarrhea, hypomagnesemia, myoclonus, nausea, and seizure-like phenomena. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Meitheal Pharmaceuticals Inc. at 1-844-824-8426 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. The safety of methylene blue injection in adults with acquired methemoglobinemia was assessed in 24 patients who received at least 1 dose of methylene blue injection [see Clinical Studies (14) ] . Most doses administered were 1 mg/kg (88.5%), but doses from 1 mg/kg to 2 mg/kg were administered. All patients received at least one dose of methylene blue injection; two received two doses. Serious adverse reactions occurred in 4.2% of patients who received methylene blue injection. A serious adverse reaction of seizure-like phenomenon was reported in one patient. Adverse reactions (≥2%) included headache, hypokalemia, diarrhea, hypomagnesemia, myoclonus, nausea, and seizure-like phenomena. The safety of methylene blue injection in pediatric patients with acquired methemoglobinemia was assessed in two retrospective case series that included two pediatric patients treated with methylene blue injection and 12 treated with another methylene blue product. […]
Interactions with other medicines
Clinically significant drug interactions with methylene blue injection are described below: The concomitant use of methylene blue injection with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome. Although the mechanism is not clearly understood, literature reports suggest methylene blue is a potent reversible inhibitor of monoamine oxidase. Avoid concomitant use of methylene blue injection with medicinal products that enhance serotonergic transmission including antidepressants like SSRIs (selective serotonin reuptake inhibitors), SNRIs (serotonin and norepinephrine reuptake inhibitors), MAOIs (monoamine oxidase inhibitors), bupropion, buspirone, clomipramine, mirtazapine, linezolid, opioids, and dextromethorphan because of the potential for serious CNS reactions, including potentially fatal serotonin syndrome. If the intravenous use of methylene blue injection cannot be avoided in patients treated with serotonergic medicinal products, choose the lowest possible dose and observe the patient closely for CNS effects for up to 4 hours after administration [see Warning and Precautions (5.1) and Clinical Pharmacology (12.3) ] .
Use in specific groups
Pregnancy: Only use during pregnancy if the potential benefit justifies the potential risk to the fetus. ( 8.1 ) Lactation: Discontinue breast-feeding for up to 8 days after treatment. ( 8.2 ) Hepatic Impairment: Monitor patients longer for toxicity and drug interactions due to delayed clearance. ( 8.7 ) 8.1 Pregnancy Risk Summary Methylene blue injection may cause fetal harm when administered to a pregnant woman. Intra-amniotic injection of pregnant women with a methylene blue class product during the second trimester was associated with neonatal intestinal atresia and fetal death. Methylene blue produced adverse developmental outcomes in rats and rabbits when administered orally during organogenesis at doses at least 32 and 16 times, respectively, the clinical dose of 1 mg/kg ( see Data ) . Advise pregnant women of the potential risk to a fetus. In the U.S. general population, the estimated background risks of major birth defects and miscarriage in clinically recognized pregnancies are 2-4% and 15-20%, respectively. Clinical Considerations Fetal/neonatal adverse reactions Intra-amniotic injection of a methylene blue class product hours to days prior to birth can result hyperbilirubinemia, hemolytic anemia, skin staining, methemoglobinemia, respiratory distress and photosensitivity in the newborn. Following administration of methylene blue injection to a pregnant woman at term, observe the newborn for these adverse reactions and institute supportive care. Data Animal Data Methylene blue was administered orally to pregnant rats at doses of 50 to 350 mg/kg/day, during the period of organogenesis. Maternal and embryofetal toxicities were observed at all doses of methylene blue and were most evident at the 200 and 350 mg/kg/day doses. Maternal toxicity consisted of increased spleen weight. Embryo-fetal toxicities included reduced fetal weight, post-implantation loss, edema, and malformations including enlarged lateral ventricles. The dose of 200 mg/kg (1,200 mg/m 2 ) in rats is approximately 32 times a clinical dose of 1 mg/kg based on body surface area. […]
If too much is taken
Hypotension, wheezing and reduced oxygenation have been reported in patients who received methylene blue class products in single doses of 3 mg/kg or more. Administration of large intravenous doses (cumulative dose ≥ 7 mg/kg) of a methylene blue class product caused nausea, vomiting, precordial pain, dyspnea, tachypnea, chest tightness, tachycardia, apprehension, tremor, mydriasis, blue staining of the urine, the skin and mucous membranes, abdominal pain, dizziness, paresthesia, headache, confusion, mild methemoglobinemia (up to 7%) and electrocardiogram changes (T-wave flattening or inversion). These effects lasted 2-12 hours following administration. A severe overdosage (single dose of 20 mg/kg or more) of a methylene blue class product caused severe intravascular hemolysis, hyperbilirubinemia and death. In case of overdose of methylene blue injection, maintain the patient under observation until signs and symptoms have resolved, monitor for cardiopulmonary, hematologic and neurologic toxicities, and institute supportive measures as necessary.
Storing it safely
Storage Store at 20° to 25°C (68° to 77°F); excursions permitted to 15° to 30°C (59° to 86°F). [See USP Controlled Room Temperature.] Any unused product or waste material should be disposed of in accordance with local practice. Do not refrigerate or freeze. Keep the vial in the original package to protect from light. The container closure is not made with natural rubber latex.
Before you take anything new
Tell your pharmacist or doctor about every medicine you take — including ones bought without a prescription, herbal products and supplements. Interactions are one of the most common avoidable causes of harm from medicines, and a pharmacist can check your full list in a couple of minutes.
This page is built from the openFDA record of the U.S. Food and Drug Administration's approved labelling for this product, effective 27 January 2025. Label text has been shortened and reformatted for readability; safety wording has not been altered in meaning. FDA labelling describes products approved in the United States — brand names, strengths, formulations and approved uses may differ in your country. Always read the leaflet that comes with your own pack. PocketsInfo is not affiliated with, and is not endorsed by, the FDA. Retrieved 2026-07-30.