Methylene Blue Injection

Methylene Blue Injection

Available presentation(s): 15, 30, 100 mL. Verify the exact concentration and total active quantity on the prescription and dispensing label.

Introduction: Methylene blue is an oxidation-reduction agent with approved use for acquired methaemoglobinaemia in certain products. Other intravenous uses are specialist/off-label. It is a potent monoamine oxidase A inhibitor.

Dosage: For methaemoglobinaemia, follow the applicable approved label and weight-based protocol, including repeat-dose limits and response monitoring. The 1% solution is 10 mg/mL; prescribing and administration must be in milligrams and verify concentration. Do not use routine wellness dosing.

Mechanisms of Action: At therapeutic concentrations, NADPH-dependent methaemoglobin reductase reduces methylene blue to leucomethylene blue, which reduces ferric methaemoglobin to functional ferrous haemoglobin. It also inhibits MAO-A.

Contraindications & Precautions: Contraindicated in severe hypersensitivity and generally avoided in G6PD deficiency because of haemolysis and poor response. Use caution in renal impairment. Pulse oximetry and some laboratory values may be distorted. Excess dosing can paradoxically increase methaemoglobinaemia.

Interactions: Potentially life-threatening serotonin syndrome with serotonergic medicines, including SSRIs/SNRIs, MAOIs, clomipramine, linezolid, tramadol and some opioids. Review all medicines before use.

Adverse Reactions / Side Effects: Blue-green urine/skin, nausea, headache, dizziness, sweating, abdominal pain and injection-site reactions occur. Serious effects include serotonin syndrome, haemolysis, anaphylaxis, hypertension, arrhythmia and paradoxical methaemoglobinaemia.

Pregnancy & Breastfeeding: May cause fetal harm, particularly with intra-amniotic exposure. Use in pregnancy only for a serious indication when benefits outweigh risks. Breastfeeding interruption may be required according to dose/product guidance.

Storage: Store under the conditions stated on the Optimus dispensing label and product-specific worksheet. Protect from light where labelled. Do not freeze unless explicitly validated. Maintain cold chain if the label requires refrigeration. Do not use after the assigned beyond-use date or if there is visible particulate matter, precipitation, colour change, loss of container integrity or evidence of improper storage. Once entered, follow the validated in-use time; do not assume a compounded vial is multi-dose.

References

• New Zealand Formulary (NZF), current online edition; product-specific approved data sheets where available; USP Pharmaceutical Compounding—Sterile Preparations; and Optimus Healthcare validated formulation, sterility/endotoxin controls and assigned beyond-use date.
• DailyMed. Methylene Blue Injection—prescribing information, current edition. https://dailymed.nlm.nih.gov/
• US FDA. Compounding and the FDA: Questions and Answers. Updated 16 September 2025. https://www.fda.gov/drugs/human-drug-compounding/compounding-and-fda-questions-and-answers