methylthioninium chloride at a glance
Medicine class
Antidote
Licensed use
Acute symptomatic medicine- or chemical-induced methaemoglobinaemia
Administration
Slow intravenous injection by a healthcare professional
Expected colour change
Urine or stools may become blue-green and skin may appear blue temporarily
What is methylthioninium chloride used for?
The selected product is licensed for:
Acute symptomatic methaemoglobinaemia caused by medicines or chemicals in adults, children and newborn babies.
How does methylthioninium chloride work?
Methaemoglobin cannot carry oxygen effectively. Methylthioninium chloride helps convert it back into functional haemoglobin through an NADPH-dependent pathway in red blood cells. This is why it may be ineffective and cause haemolysis in G6PD deficiency.
methylthioninium chloride preparations and strengths
Injection
Route: Parenteral
Strengths: 5 mg/mL
How to take methylthioninium chloride
This is a hospital treatment given slowly into a vein by a healthcare professional.
Tell the clinical team about all medicines taken recently, especially antidepressants, anxiety treatments, opioids and cough medicines containing dextromethorphan.
Mention G6PD deficiency, kidney disease, diabetes, pregnancy or breastfeeding where circumstances permit.
Do not drive or operate machinery if dizziness, confusion or visual disturbance occurs.
methylthioninium chloride side effects
Common or expected effects
- Dizziness, tingling or numbness, or an unusual taste
- Nausea, vomiting, abdominal pain or headache
- Sweating, anxiety, or pain in a limb or at the injection site
- Temporary blue skin and blue-green urine
Get urgent medical advice
- Severe allergic reaction, including facial or throat swelling and breathing difficulty
- Serotonin syndrome, including agitation, confusion, fever, shaking, abnormal muscle tone or reduced consciousness
- Haemolytic anaemia, with pallor, weakness, jaundice or worsening breathlessness
- Irregular heartbeat, marked blood-pressure changes, chest pain or worsening hypoxia
- Local tissue damage around the injection site
methylthioninium chloride in pregnancy
Human pregnancy data are inadequate and animal studies found reproductive toxicity. Use during pregnancy is not recommended unless clearly necessary, such as life-threatening methaemoglobinaemia.
methylthioninium chloride while breastfeeding
It is unknown whether methylthioninium chloride enters human milk, and risk to a breastfed child cannot be excluded. The product information advises temporarily interrupting breastfeeding after treatment; the clinical team can help plan feeding and milk expression.
methylthioninium chloride interactions
A complete recent medicines history is essential, particularly in an emergency.
SSRIs and SNRIs
Combining serotonergic antidepressants with methylthioninium chloride can cause potentially fatal serotonin syndrome and should be avoided where possible.
Other serotonergic medicines
Bupropion, buspirone, clomipramine, mirtazapine and monoamine oxidase inhibitors may increase the risk of serious central nervous system toxicity.
Serotonergic opioids and dextromethorphan
Tramadol, fentanyl, pethidine and dextromethorphan may add to the risk of serotonin syndrome.
Common questions about methylthioninium chloride
Answers are fully visible for fast scanning and source review.
Is methylthioninium chloride the same as methylene blue?
Yes. Methylene blue is a commonly used alternative name.
Can it be used in children?
The licensed indication includes children and newborn babies. Very young infants require particular caution.
Why is G6PD deficiency important?
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.