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Methylene Blue

Methylene blue is a visible blue dye and an active drug. The US PROVAYBLUE indication is acquired methemoglobinemia in adults and children; fistula localization, urinary leak testing and other surgical dye uses are off-label. Its redox and monoamine-oxidase effects mean that dye use still requires medication and contraindication review.[1]

Formulation and pharmacology​

PROVAYBLUE contains 5 mg/mL; other products may have different concentrations. Verify the actual vial rather than assuming every injectable product is 1% (10 mg/mL).[1] Methylene blue appears in urine, although urinary color and the timing of efflux can vary. Its visible-light role differs from fluorescence imaging with a compatible camera; an ICG-oriented NIR system is not automatically suitable.[1][2]

Surgical applications​

Fistula localization​

Dilute intravesical methylene blue can help identify communication between the bladder and vagina, and an office dye test allows same-day diagnosis.[3] The classic three-swab (tampon) test places three separate gauze swabs in the vagina (apex, mid, distal), fills the bladder retrograde through a catheter with lightly tinted saline, has the patient cough, Valsalva or walk, watches throughout for blue irrigant backflow at the meatus, then removes and inspects the swabs after 10 minutes (up to 30 minutes for a tiny tortuous fistula).[8] Blue on the upper swab points to a vesicovaginal fistula; blue only on the distal swab suggests urethral leakage or a distal urethrovaginal fistula; a swab that is only wet with clear fluid raises the question of a ureteral source. In a double-dye examination, oral phenazopyridine colors upper-tract urine orange while the bladder contains blue solution. Blue vaginal staining supports a bladder or urethral communication; orange leakage without blue suggests a ureteral source.[8] Mixed colors, urethral leakage, contamination, intermittent leakage and inadequate filling can complicate interpretation. Follow the clinical fistula evaluation pathway and obtain anatomical confirmation as indicated.

Urinary anastomosis and bladder leak testing​

Gentle filling with saline or a locally specified dilute dye can identify visible extravasation. Select the fill volume and pressure for the repair and the bladder's capacity rather than a fixed volume. Neither a negative leak test nor a visible ureteral jet excludes later ischemic failure.

Ureteral visualization​

IV methylene blue has been studied as an off-label aid, including near-infrared fluorescence imaging. In a 12-patient lower-abdominal-surgery feasibility study performed after exposure of the ureters, IV doses of 0.25–1 mg/kg visualized both ureters within 10 minutes; signal remained visible at the final 60-minute observation, with no significant difference in signal-to-background ratio between dose groups.[4] In laparoscopic colorectal surgery (n = 10, 0.125–1.0 mg/kg), the ureter was detected in only five patients, and the signal appeared only after the ureter was already visible in white light.[5] The 2023 WSES guideline describes limited clinical evidence and suggests considering IV methylene blue as a fluorescent adjunct for selected patients undergoing minimally invasive emergency digestive surgery when ureter localization is expected to be difficult ; use also depends on the intended imaging method, patient safety and local protocol.[2] Concentrated intravesical dye can obscure the field. Do not use an unverified intraventricular or intrathecal dye technique.

Urethral stricture mapping during urethroplasty​

Methylene blue instilled retrograde into the urethra at the start of urethroplasty stains the strictured urothelium, while normal urethra stays pink. Joshi and colleagues at Kulkarni's center diluted 5 mL of 10 mg/mL dye in 10 mL of saline, injected it gently through the meatus and applied a penile clamp for about 5 minutes so the dye could pass the narrow lumen. In 492 consecutive anterior urethroplasties (2010–2014), the strictured segment stained in 464 (94%). Staining was minimal or absent in 28 (6%), dye extravasated into the spongiosum in 8 (2%) and staining was dense distal to the narrow lumen in 22 (4%). In representative biopsies, stained urethra showed stricture and unstained urethra showed normal urothelium. A single surgeon judged the staining, and no allergic complications were reported. The authors attribute the uptake to gaps between cells of the diseased epithelium, since normal urothelium is impermeable; the molecular basis is unknown.[11]

The stain has two uses in that series. It shows the length that needs augmentation, and the graft is carried beyond the stained segment at both ends. In a near-obliterative stricture that a guidewire cannot cross, it marks the lumen so the urethrotomy enters it rather than creating a false passage. Forceful injection causes extravasation that makes the stricture harder to read.[11] Other units use the same step: Mousa and colleagues passed a guidewire under urethroscopy, then injected 5–10 mL intraurethrally before the midline perineal incision for ventral and dorsal onlay buccal graft repairs.[12] The step also appears in the Palminteri double-face, transmeatal ventral inlay and dorsal circumcising approach descriptions.

Methylene blue spongiography assesses spongiofibrosis in short bulbar strictures of unclear cause. After the bulbar urethra is exposed, insulin needles are placed in the spongiosum proximal to, at and distal to the stricture; the proximal bulb may be clamped to limit inflow from the bulbar artery, and dye is injected through the distal needle. In Joshi and colleagues' 22-patient series of short idiopathic bulbar strictures, the team interpreted proximal-needle efflux as little spongiofibrosis and performed augmentation without transection; with no efflux, they interpreted significant spongiofibrosis and performed excision with primary anastomosis.[11] In 22 idiopathic short bulbar strictures (median length 1.2 cm), dye crossed in 18 (82%) and transection was avoided; 4 (18%) had excision and anastomosis. The report gives no stricture-free outcomes for either group.[11]

Disease can extend past the stricture seen at surgery. In 15 men with idiopathic stricture, in whom methylene blue was used to locate damaged urothelium, 93% had scarring in biopsies taken 1 and 2 cm proximal and distal to the stricture.[13] Localization without dye is also described: Kuo and colleagues identify the stricture by cystoscopy and external transillumination and place a suture through the urethra at its distal end under endoscopic control (35 bulbar urethroplasties, one later optical urethrotomy for recurrence).[14] See Principles of Urethral Reconstruction for the operative context.

Labeled methemoglobinemia treatment​

For PROVAYBLUE, the usual label regimen is 1 mg/kg IV over 5–30 minutes. One additional 1 mg/kg dose may be given after one hour if methemoglobin remains above 30% or symptoms persist. Persistent disease after two doses requires an alternative approach and expert toxicology or hematology support. For eGFR 15–59 mL/min/1.73 m², the label recommends a single 1 mg/kg dose; do not automatically repeat. If dilution is needed, use the label's 5% dextrose instructions; sodium chloride can reduce solubility. These IV treatment instructions are separate from off-label bladder instillation protocols.[1]

Contraindications and important precautions​

  • G6PD deficiency is a contraindication, as are severe hypersensitivity reactions to methylene blue or another thiazine dye.[1]
  • Boxed warning: serotonin syndrome, potentially fatal, with serotonergic drugs and opioids. Review SSRIs, SNRIs, MAO inhibitors, opioids, linezolid and dextromethorphan with anesthesia/pharmacy before IV methylene blue use. Avoid concomitant use; if IV PROVAYBLUE is unavoidable in a patient taking a serotonergic drug, the label directs the lowest possible dose and close observation for CNS effects for up to 4 hours after administration.[1] The label advises avoiding serotonergic drugs for 72 hours after the last dose.[6][7] Serotonin syndrome has been reported after a 7 mg subcutaneous injection for sentinel node mapping in a patient taking fluoxetine who also received fentanyl,[6] and after methylene blue infusion for parathyroid localization in a patient on antidepressants.[7] These reports involve parenteral dosing; the risk from dilute intravesical use is not quantified, but absorption through inflamed or freshly repaired urothelium is plausible.
  • Hemolysis may occur, sometimes delayed. Methemoglobinemia due to aniline or dapsone may persist or rebound after an initial response; monitor until it resolves.[1]
  • The label notes that intra-amniotic injection of a methylene blue class product in the second trimester was associated with neonatal intestinal atresia and fetal death. Otherwise pregnancy requires an individualized benefit/risk assessment; the label includes pediatric treatment. The label advises discontinuing breastfeeding during treatment and for up to 8 days afterward.[1]
  • Renal impairment increases exposure, and hepatic impairment may prolong toxicity and interaction risk.[1]

Monitoring and practical points​

Methylene blue may cause an artifactual decrease, not increase, in pulse-oximeter saturation. Inform anesthesia, assess for true hypoxemia and use an appropriate alternative measurement when needed. The label advises an arterial blood sample for oxygen saturation if it is needed during or shortly after an infusion. The label reports a fall in the Bispectral Index after methylene blue; when PROVAYBLUE is given during surgery, tell anesthesia and use an alternative method for assessing anesthetic depth.[1] Urine color and some laboratory assays can also be affected. Record the product, dose, concentration and route; use a reviewed local dilution protocol for surgical applications.[1]

Practical points for dye use:

  • Injectable methylene blue stock is available at 5–10 mg/mL; dilute before intravesical dye testing because overly concentrated dye can stain the field and make interpretation difficult.[1][9][10]
  • Have the dye, catheter and swabs ready before the test.
  • Blue staining of the field can degrade later white-light or fluorescence perfusion assessment, so sequence ICG or other imaging first when both are planned.
  • Blue-green urine and transient staining of skin are expected and resolve; hypersensitivity and hemolysis are the events to watch for.
  • Dye-test volumes and concentrations vary by unit. Hancock and Browning describe dilute methylene blue for the bladder-filling swab test, starting with about 60 mL and repeating with up to 200 mL if the initial swabs are unstained.[9]

See Also​

References​

1. PROVAYBLUE (methylene blue) injection. US prescribing information (American Regent; SPL version effective May 2025; boxed warning 11/2023). DailyMed.

2. de'Angelis N, Schena CA, Marchegiani F, et al. 2023 WSES guidelines for prevention, detection and management of iatrogenic urinary tract injuries during emergency digestive surgery. World J Emerg Surg. 2023;18:45. doi:10.1186/s13017-023-00513-8.

3. Thayalan K, Parghi S, Krause H, et al. Vesicovaginal fistula following pelvic surgery: Our experiences and recommendations for diagnosis and prompt referral. Aust N Z J Obstet Gynaecol. 2020;60(3):449-453. doi:10.1111/ajo.13134

4. Verbeek FP, van der Vorst JR, Schaafsma BE, et al. Intraoperative near infrared fluorescence guided identification of the ureters using low dose methylene blue: a first in human experience. J Urol. 2013;190(2):574-9. doi:10.1016/j.juro.2013.02.3187

5. Al-Taher M, van den Bos J, Schols RM, et al. Fluorescence Ureteral Visualization in Human Laparoscopic Colorectal Surgery Using Methylene Blue. J Laparoendosc Adv Surg Tech A. 2016;26(11):870-875. doi:10.1089/lap.2016.0264

6. Larson KJ, Wittwer ED, Nicholson WT, et al. Myoclonus in patient on fluoxetine after receiving fentanyl and low-dose methylene blue during sentinel lymph node biopsy. J Clin Anesth. 2015;27(3):247-51. doi:10.1016/j.jclinane.2014.11.002

7. Rowley M, Riutort K, Shapiro D, et al. Methylene blue-associated serotonin syndrome: a 'green' encephalopathy after parathyroidectomy. Neurocrit Care. 2009;11(1):88-93. doi:10.1007/s12028-009-9206-z

8. Elneil S, Romanzi L, Goh J, et al. "An International Continence Society (ICS) report on the terminology for female pelvic floor fistulas." Neurourol Urodyn. 2020;39(8):2040–2071. doi:10.1002/nau.24508

9. Hancock B, with Browning A. Practical Obstetric Fistula Surgery. Royal Society of Medicine Press; 2009. Chapter 2, Diagnosis, p.17. Full text.

10. Methylene blue injection, USP (5 mg/mL and 10 mg/mL). US prescribing information (Zydus Pharmaceuticals USA Inc.; updated April 2026). DailyMed.

11. Joshi P, Kaya C, Surana S, et al. A novel method in decision making for the diagnosis of anterior urethral stricture: using methylene blue dye. Turk J Urol. 2017;43(4):502-506. doi:10.5152/tud.2017.72368

12. Mousa A, Eissa A, Raheem AA, Zoeir A. Ventral versus dorsal onlay buccal mucosal graft urethroplasty for non-traumatic proximal bulbar urethral strictures in sexually active men: erectile and urinary functions. World J Urol. 2025;43(1):87. doi:10.1007/s00345-025-05441-7

13. Desai D, Harrison W, Raveenthiran S, et al. UrethroNAV: the aetiology and extent of idiopathic urethral stricture in an Australian population. Transl Androl Urol. 2024;13(3):423-432. doi:10.21037/tau-23-549

14. Kuo TL, Venugopal S, Inman RD, Chapple CR. Surgical tips and tricks during urethroplasty for bulbar urethral strictures focusing on accurate localisation of the stricture: results from a tertiary centre. Eur Urol. 2015;67(4):764-770. doi:10.1016/j.eururo.2014.12.029