Methylene Blue Contraindications

Methylthioninium chloride must not be used by individuals taking certain medications for depression or anxiety that affect serotonin. When used in combination with the following drugs, methylthioninium chloride can cause serotonin syndrome, a potentially life-threatening condition:

• Selective serotonin reuptake inhibitors (SSRIs), e.g., citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine, sertraline, and zimelidine
• Bupropion
• Buspirone
• Clomipramine
• Mirtazapine
• Venlafaxine
• Monoamine oxidase inhibitors (MAOIs)
• Certain opioids (tramadol, fentanyl, pethidine, and dextromethorphan)

It is also contraindicated in patients with Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency.
G6PD deficiency increases the sensitivity of erythrocytes to oxidative stress. It clinically manifests as neonatal jaundice, acute hemolysis, and more rarely, chronic hemolytic anemia. Individuals with this disorder may also be asymptomatic.
It is an X-linked hereditary disorder that occurs primarily in Africa, Asia, the Mediterranean, and the Middle East.

Pregnancy and breastfeeding are also contraindicated.