Methylene Blue

Description

Clinical content written by Julia Ossman, 2027 PharmD Candidate, Philadelphia College of Pharmacy

Methylene Blue

Methylene blue, also called methylthioninium chloride, has historically been used as a diagnostic dye and as a treatment for methemoglobinemia, but it has potential for off-label use in many other clinical situations. Dosing may be prescribed based on its intended use, which can vary from patient to patient. Here at Zarina, we can compound methylene blue into capsules of various strengths.

Pronunciation: METH-uh-leen bloo

Active Ingredient & How It Works

Methylene Blue — Drug class: antidote, diagnostic agent. Also available commercially under the brand name ProvayBlue. Methylene blue promotes a reduction-oxidation conversion of methemoglobin to hemoglobin, restoring hemoglobin’s ability to efficiently carry oxygen in the blood. It can also carry electrons to cytochrome C, bypassing parts of the mitochondrial electron transport chain that are not functioning properly, and produces vasoconstrictive effects by inhibiting nitric oxide synthase and guanylate cyclase.

Possible Side Effects

Common side effects may include dizziness, nausea, headache, diarrhea, teeth staining, and discoloration of urine or skin.

Tell your doctor immediately if you experience any of the following while taking methylene blue:

🚨 Allergic reaction: Trouble breathing, swelling of the face, rash, hives, or itching.

🚨 Serotonin syndrome: Agitation, hallucinations, delirium, fast heart rate, dizziness, seizures, nausea, vomiting, or diarrhea.

🚨 Hemolytic anemia: Weakness, pale or yellowish skin, or dizziness.

Drug Interactions

Avoid concomitant use with serotonin reuptake inhibitors (SSRIs), serotonin-norepinephrine reuptake inhibitors (SNRIs), monoamine oxidase inhibitors (MAOIs), and opioids. Taking serotonergic drugs together with methylene blue increases the risk of serotonin syndrome.

Warning: Do not take this medication if you have glucose-6-phosphate dehydrogenase (G6PD) deficiency, due to an increased risk of hemolytic anemia.

Administration & Dosing

Use this medication exactly as prescribed. Contact your healthcare provider for specific dosing instructions.

Pregnancy, Breastfeeding & Pediatrics

Methylene blue may have the potential to cause fetal harm. Consult your healthcare provider if you are pregnant to discuss the risks and benefits. It is unknown whether methylene blue is excreted in human breast milk; one manufacturer recommends discontinuing breastfeeding during treatment and for up to 8 days after administration due to an increased risk of adverse reactions. Methylene blue may be safe and effective in neonates, infants, children, and adolescents — consult your healthcare provider for more information.

⚠️ Disclaimer: This information is generalized and not intended as specific medical advice. If you have questions about the use of your prescription, please contact your prescriber.

References

– DailyMed. PROVAYBLUE (methylene blue) injection [Internet]. Bethesda (MD): U.S. National Library of Medicine; 2025 May 28 [cited 2026 Jun 22]. Available from: dailymed.nlm.nih.gov

– Drugs.com. Methylene blue: uses, dosage, side effects, warnings [Internet]. Drugsite Trust; 2025 May 5 [cited 2026 Jun 22]. Available from: drugs.com

– Tatarinova O, Lund K, Bain BJ. Beware of methylene blue in possible G6PD deficiency. Am J Hematol. 2024;99(10):2016-2017. doi:10.1002/ajh.27324.