About methylthioninium chloride hydrate
Thiazine dye; diagnostic and antidote agent
Used for
- Treats methemoglobinemia by restoring normal hemoglobin function.
- May be used to locate certain structures during surgery or diagnostic procedures.
Usual adult dose
For methemoglobinemia: usually 1 mg/kg intravenously over 5–30 minutes; a further dose may be given if needed.
Usual dose in children
For methemoglobinemia: usually 1 mg/kg intravenously over 5–30 minutes; repeat dosing requires specialist assessment.
Common side effects
- Blue or green urine, skin, or other body fluids
- Nausea, vomiting, abdominal pain, or headache
- Raised blood pressure or rapid heartbeat
- Serotonin syndrome or haemolytic anaemia
Important warnings
- Can cause severe haemolysis in people with G6PD deficiency.
- May worsen methemoglobinemia at high doses or with repeated dosing.
- Can cause serotonin syndrome with serotonergic medicines, including some antidepressants and opioids.
- May interfere with pulse oximeter readings and laboratory tests.
Pregnancy
Use only when clearly needed; treatment of serious methemoglobinemia may outweigh fetal risks. Specialist assessment is required.
Breastfeeding
Breastfeeding is generally avoided during treatment and for up to eight days afterward, due to potential harm to the infant.
Interactions
- Serotonergic medicines, including SSRIs, SNRIs, and some opioids, increase serotonin syndrome risk.
- Other medicines that cause haemolysis may increase red-cell damage.
- May interfere with dyes or tests used during surgery and diagnostic procedures.
AI-generated from general medical knowledge, not from this product's official leaflet. It may be incomplete or out of date. Not medical advice — ask a pharmacist or doctor before making any decision.