Methylene Blue trihydrate
[CAS# 7220-79-3]

Identification

• Classification: API >> Special medicine >> Antidote
• Name: Methylene Blue trihydrate
• Synonyms: C.I. 52015 trihydrate; Basic Blue 9 trihydrate; 3,7-Bis(dimethylamino)phenothiazin-5-ium chloride
• Molecular Formula: C₁₆H₁₈ClN₃S.3(H₂O)
• Molecular Weight: 373.90
• CAS Registry Number: 7220-79-3
• EC Number: 615-731-6
• SMILES: CN(C)C1=CC2=C(C=C1)N=C3C=CC(=[N+](C)C)C=C3S2.O.O.O.[Cl-]

Properties

• Melting point: 190 °C (decomp.) (Expl.)
• Water solubility: 4 g/100 mL

Safety Data

• Hazard Symbols: GHS07;GHS08 Warning
• Risk Statements: H302-H315-H319-H335-H373
• Safety Statements: P260-P261-P264-P264+P265-P270-P271-P280-P301+P317-P302+P352-P304+P340-P305+P351+P338-P319-P321-P330-P332+P317-P337+P317-P362+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	4	H302
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335
Specific target organ toxicity - repeated exposure	STOT RE	2	H373

Discovery and Applications

Methylene Blue trihydrate is a chemical compound widely used in various fields, including medicine, biology, and chemistry. Its chemical structure is based on a phenothiazine derivative, and it is known for its distinctive blue color. Methylene Blue was first synthesized in 1876 by the German chemist Heinrich Caro, and its development marked the beginning of its various applications, both in scientific research and practical uses.

In the medical field, Methylene Blue trihydrate has been used primarily as a diagnostic and therapeutic agent. It has been employed as a dye in several medical procedures, such as in sentinel lymph node mapping during cancer surgeries. It is also used in surgeries to trace the path of lymphatic drainage, helping surgeons to identify and remove lymph nodes that may be affected by cancer. Methylene Blue has also been utilized as a treatment for methemoglobinemia, a condition in which the blood is unable to carry oxygen effectively due to a higher than normal level of methemoglobin. In this context, Methylene Blue works by reducing methemoglobin back to its normal state, allowing red blood cells to resume normal oxygen transport.

In addition to its medicinal applications, Methylene Blue trihydrate has a long history in microbiological and biochemical research. It is commonly used as a staining agent in laboratories for the identification and observation of microorganisms under a microscope. The compound is particularly useful in the identification of protozoa and in the staining of various cellular structures, such as in the study of bacterial cultures and tissues. Methylene Blue is also employed in the field of cell biology for its ability to interact with cellular components, particularly in identifying viable and non-viable cells in cell culture experiments.

Methylene Blue trihydrate has also found applications in the field of environmental science, where it is used in water treatment and in analytical chemistry for redox reactions. The compound is used to measure the concentration of dissolved oxygen in water, and it serves as a redox indicator in various analytical procedures. Furthermore, its ability to absorb light at specific wavelengths has made it a useful compound in spectrophotometry.

While Methylene Blue has several beneficial applications, it is important to use it with caution, particularly in clinical settings. In medical treatments, the compound can cause side effects such as nausea, vomiting, and skin discoloration. It is contraindicated in individuals with hypersensitivity to the compound and should be used with caution in patients with G6PD deficiency, as it may precipitate hemolysis.

In summary, Methylene Blue trihydrate is a versatile chemical compound with a wide range of applications in medicine, research, and environmental science. Its use as a diagnostic tool, therapeutic agent, and laboratory stain underscores its importance in both clinical and scientific settings. The compound has been a valuable tool in understanding cellular processes and in the treatment of certain medical conditions, such as methemoglobinemia.

References

2025. Methylene blue-functionalized ZIF-8/Au nanoparticle composites based ratiometric electrochemical sensor for reliable detection of methyl parathion in vegetables. Food Chemistry.
DOI: 10.1016/j.foodchem.2024.141812

2025. Rapid virus inactivation by nanoparticles-embedded photodynamic surfaces. Journal of Colloid and Interface Science.
DOI: 10.1016/j.jcis.2024.10.114

2015. A novel set of symmetric methylene blue derivatives exhibits effective bacteria photokilling - a structure-response study. Photochemical & Photobiological Sciences, 14(2).
DOI: 10.1039/c4pp0039h