Related Experiment Video
Updated: Jul 17, 2025
Optimized Griess Reaction for UV-Vis and Naked-eye Determination of Anti-malarial Primaquine
Published on: October 11, 2019
Spectrophotometric analysis of purple urine secondary to methylene blue and hydroxocobalamin co-administration
Jeremy Hardin1,2,3, Henrik Galust4,5,6, Richard Franklin Clark4,6
1Division of Medical Toxicology, Department of Emergency Medicine, UC San Diego Health, 200 W. Arbor Dr. #8676, San Diego, CA, 92103, USA. jrhardin@health.ucsd.edu.
Background:
The development of purple urine after methylene blue (methylthioninium chloride) and hydroxocobalamin co-administration is a rare clinical entity that has not been fully elucidated. A 47-year-old male presented to the emergency department with hypotension, cyanosis, and depressed mental status. The patient was noted to have profound peripheral and central cyanosis, as well as chocolate-colored arterial blood. He was treated with both methylene blue and hydroxocobalamin and developed purple urine for approximately 1 week.
Methods:
Color chromatography was performed by placing the patient's urine directly onto absorbent filter paper. Urine spectrophotometry was performed utilizing the NanoDrop One/One C UV-Vis Spectrophotometer.
Results:
Color chromatography of the urine was demonstrated clear separation of distinct red and blue phases. Urine spectrophotometry demonstrated near perfect overlap between the methylene blue + hydroxocobalamin absorbance spectrum and the patient's purple urine absorbance spectrum.
Conclusion:
Purple urine secondary to methylene blue and hydroxocobalamin co-administration is due to combined urinary excretion of methylene blue (blue) and hydroxocobalamin (red), and not a novel purple metabolite. We anticipate that this is going to be an increasingly common clinical entity as the roles of both hydroxocobalamin and methylene blue expand from toxicologic antidotes to adjunct therapies for vasoplegia, poor cardiac output, and sepsis.
