The blue pigment known as indigo has a long and varied history, from its use in textiles to its roles in modern medicine. However, the term "drug indigo" does not refer to a single substance but rather encompasses two very different compounds with distinct pharmacological profiles and applications: indigotindisulfonate sodium (indigo carmine) and indigo naturalis. One is a synthetic diagnostic tool for surgical procedures, while the other is a complex herbal mixture with therapeutic effects on inflammatory conditions.
The Diagnostic Dye: Indigotindisulfonate Sodium
What is Indigo Carmine?
Also known as indigo carmine, indigotindisulfonate sodium is a synthetic blue dye primarily used as a diagnostic agent. Bludigo is a brand name for this dye, which received FDA approval in 2022 for specific uses. It's injected to aid diagnostic procedures rather than treating a disease.
How It Works
Indigotindisulfonate sodium is a biologically inert dye. It is quickly filtered by the kidneys after injection and excreted in the urine, turning it deep blue. This visual contrast helps surgeons track and assess the integrity of the ureters and bladder during procedures like cystoscopy, making anatomical structures easier to see. The effect is temporary as the dye is cleared by the kidneys.
Uses in Medicine
This dye is mainly used for visualization during surgery. It helps surgeons confirm ureteral integrity, localize ureteral orifices during cystoscopy, and identify fistulous tracts.
Side Effects and Precautions
Possible side effects include rare but severe cardiovascular reactions like arrhythmia and hypertension. Hypersensitivity reactions, including anaphylaxis, are also possible. The dye can interfere with pulse oximetry readings. Temporary blue urine discoloration is expected, and skin discoloration can occur with high doses.
The Herbal Medicine: Indigo Naturalis
What is Indigo Naturalis?
Indigo naturalis, also known as Qing dai in Traditional Chinese Medicine (TCM), is an herbal preparation from plants like Strobilanthes cusia and Isatis tinctoria. It has been used for centuries for its anti-inflammatory, antioxidant, and antimicrobial properties. Its powder contains compounds including indigo, indirubin, and tryptanthrin.
Active Components and Pharmacology
The active components of indigo naturalis provide its therapeutic effects. They modulate immune responses, inhibiting inflammatory pathways and reducing pro-inflammatory cytokines. Compounds like indirubin and tryptanthrin can also regulate cell proliferation, beneficial in conditions like psoriasis. It can also help regulate gut microbiota, potentially aiding in ulcerative colitis treatment.
Clinical Applications
Indigo naturalis is studied for various inflammatory conditions. Topical applications have shown effectiveness for psoriasis. Oral use has been shown to induce remission in some patients with moderate to severe ulcerative colitis, including those resistant to conventional treatments. It has also been used in TCM for acute promyelocytic leukemia.
Potential Adverse Effects
While generally well-tolerated topically, oral use of indigo naturalis can cause side effects. Gastrointestinal issues are common. Reversible liver dysfunction has been reported with long-term oral use. Rare but serious side effects include pulmonary arterial hypertension and intestinal complications.
Comparison of Diagnostic vs. Herbal Indigo
| Feature | Indigotindisulfonate Sodium (Indigo Carmine) | Indigo Naturalis (Qing dai) |
|---|---|---|
| Classification | Synthetic diagnostic dye | Traditional herbal medicine |
| Formulation | Sterile injectable solution (e.g., Bludigo) | Processed powder or oil extract |
| Mechanism | Visual marker for urinary tract and tissues | Anti-inflammatory, anti-proliferative, immunomodulatory |
| Primary Use | Surgical visualization of ureters | Therapeutic treatment of inflammatory conditions |
| Key Indications | Cystoscopy, ureteral catheterization | Psoriasis (topical), Ulcerative Colitis (oral) |
| Adverse Effects | Cardiovascular events, hypersensitivity, oximetry interference | Gastrointestinal issues, liver dysfunction, pulmonary hypertension |
Conclusion
Indigotindisulfonate sodium and indigo naturalis are distinct substances with very different medical roles. The former is a synthetic dye for surgical visualization, while the latter is a traditional herbal medicine with anti-inflammatory properties used for conditions like psoriasis and ulcerative colitis. Recognizing this distinction is vital for understanding their applications and potential effects. For more detailed information on indigo naturalis, the NIH's database offers a comprehensive review of its properties and uses: A Comprehensive Review of the Chemistry, Pharmacokinetics, Pharmacology, Clinical Applications, Adverse Events, and Quality Control of Indigo Naturalis.
