METHYLENE BLUE
Chemistry - A thiazine dye, methylene blue occurs as dark green crystals or crystalline powderthat has a bronze-like luster. It may have a slight odor and is soluble in water and sparingly solublein alcohol. When dissolved, a dark blue solution results. Commercially available methylene blueinjection (human-labeled) has a pH from 3-4.5.
Uses, Indications - Methylene blue is used primarily for treating methemoglobinemia secondary tooxidative agents (nitrates, chlorates) in ruminants. It is also employed occasionally as adjunctive oralternative therapy for cyanide toxicity.
Intra-operative methylene blue is also being used to preferentially stain islet-cell tumors of thepancreas in dogs in order to aid in their surgical removal or in determining the animal's prognosis.
Safe use of this agent during pregnancy has not been demonstrated.
When injected SQ or if extravasation occurs during IV administration, necrotic abscesses maydevelop.
Drug Interactions; Drug/Laboratory Interactions - None located.
Storage, Stability, Compatibility
Unless otherwise instructed by the manufacturer, storemethylene blue at room temperature. Methylene blue is reportedly incompatible with caustic alkalies, dichromates, iodides, and oxidizing or reducing agents.Pharmacology - METHYLENE BLUE
Methylene blue is rapidly converted to leucomethylene blue in tissues. Thiscompound serves as a reducing agent which helps to convert methemoglobin (Fe+++) tohemoglobin (Fe++). Methylene blue is an oxidating agent, and if high doses (species dependent)are administered may actually cause methemoglobinemia.Uses, Indications - Methylene blue is used primarily for treating methemoglobinemia secondary tooxidative agents (nitrates, chlorates) in ruminants. It is also employed occasionally as adjunctive oralternative therapy for cyanide toxicity.
Intra-operative methylene blue is also being used to preferentially stain islet-cell tumors of thepancreas in dogs in order to aid in their surgical removal or in determining the animal's prognosis.
Pharmacokinetics - METHYLENE BLUE
Methylene blue is absorbed from the GI tract, but is usually administeredparenterally in veterinary medicine. It is excreted in the urine and bile, primarily in the colorlessform, but some unchanged drug may be also excreted.Contraindications, Precautions, Reproductive Safety
Methylene blue is contraindicated inpatients with renal insufficiency; hypersensitive to methylene blue; or as a intraspinal (intrathecal)injection. Because cats may develop Heinz body anemia and methemoglobinemia secondary tomethylene blue, it is considered contraindicated in this species by most clinicians. Methylene blue isconsidered to be relatively ineffective in reducing methemoglobin in horses.Safe use of this agent during pregnancy has not been demonstrated.
Adverse Effects, Warnings
The greatest concern with methylene blue therapy is the developmentof Heinz body anemia or other red cell morphological changes, methemoglobinemia, and decreasedred cell lifespans. Cats tend to be very sensitive to these effects and the drug is usually consideredto be contraindicated in them, but dogs and horses can also develop these effects at relatively lowdosages.When injected SQ or if extravasation occurs during IV administration, necrotic abscesses maydevelop.
Overdosage, Acute Toxicity
The LD50 for IV administered 3% methylene blue is approximately43 mg/kg in sheep.Drug Interactions; Drug/Laboratory Interactions - None located.