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Indigo Carmine | Structure, Properties, Uses & Side effects

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What is Indigo Carmine

Indigo Carmine or Indigotindisulfonate Sodium is an organic compound derived from Indigo using aromatic sulfonation. The sulfonation renders the compound’s solubility in water. Indigo Carmine is also called Indigotindisulfonate sodium, 5,5’- indigodisulfonic acid sodium salt,  E132, Sicovit Indigotin 85, Food Blue 1, FD&C Blue 2, ci 73015, 4 G, C.I. Acid Blue 74, Brilliant Indigo, and Indigotine. In medicine, its most well-known use is as a diagnostic agent for kidney function tests. It is also used as a food colourant, a histological dye and a two-colour pH indicator.


Chemical structure of Indigo Carmine.

IUPAC Name disodium;2-(3-hydroxy-5-sulfonato-1H-indol-2-yl)-3-oxoindole-5-sulfonate
Synonyms Indigotine; 5,5′-indigodisulfonic acid sodium salt; C.I. Acid Blue 74; C.I. Food Blue 1; Indigotindisulfonate sodium; Amacid Brilliant Blue; índigo carmim; Indaco carminio; Carmin indigo
CAS No. 860-22-0
Molecular Formula C16H8N2Na2O8S2
Molar Mass 466.4 g/mol
Appearance Dusky, purplish-blue appearance (In powder form); Blue or purplish-blue colour (Solution)
Solubility Soluble in water and alcohol; Partially soluble in other organic solvents
Melting Point 300 °C (572 °F)
PubChem CID 2723854
PubChem SID 462768915
E number E132

>> Macsen Labs is a manufacturer and supplier of INDIGO CARMINE – USP API

Note for the reader – In a few instances, this article refers to Indigo Carmine as ICN.

Uses of Indigo Carmine

Indigo Carmine is a colourant, which is clinically used for distinctive purposes. As it belongs to a class of drugs called Miscellaneous Diagnostic Dyes it can be used alone or with other medications.

For the intraoperative detection of suspected ureteral injuries throughout abdominal and pelvic surgery, ICN is indicated. This medicative product is to be injected by the blood vessel route. It is a traditional drug used as an individual agent for kidney function tests. There are several other ways of using ICN. The major uses are described below-

In Clinical Endoscopy 

Endoscopic dye spraying of the gastrointestinal tract (chromoendoscopy) was initially described in 1976. Indigo carmine could be a distinction dye that neither reacts with nor is absorbed by the mucosa, however merely pools within the tissue layer grooves and pits permitting higher topographic definition. In conjunction with improved colonoscopic equipment, this has the potential to boost the diagnostic yield by detective work on unnoticeable lesions which may otherwise be overlooked. This may be notably vital in surveillance in ulcerative colitis wherever the first changes of abnormalcy will be delicate. The study showed that the routine use of ICN dye spray throughout the complete colon is straightforward, feasible, and safe.

Indigo Carmine Injection

The solution of indigo carmine (indigotindisulfonate) is given intravenously or intramuscularly, and its appearance at the ureteral orifices is monitored using the cystoscope. The recommended initial dosage is an ampoule of 5ml having 40 mg of Indigo carmine, each mL containing 8 mg of Indigotindisulfonate Sodium and  Water for Injection q.s. The adjustment of pH is done when necessary with Citric Acid and/or Sodium Citrate. The sterility and non-pyrogenicity should be maintained.

Indigo Carmine was originally used as a kidney function test, but it is now mostly used to locate ureteral orifices during cystoscopy and ureteral catheterization.

As a positive electrode material

An experiment proves the electric nature of indigo carmine. In glucose which is known as reducing sugar and in the presence of a strong base like sodium hydroxide it reacts to form something called a glucoside anion which wants to donate a pair of electrons these electrons are then picked up by the ICN which first reduces it to a red form and then to a yellow one. Thus, Indigo carmine will work as a positive-electrode material that is not solely lithium, but additionally a sodium-electrolyte.

As a food additive

Indigo carmine gives a very rich blue colour in water. And as a food additive, It is also approved in the US and Europe. In the US and Canada, it is referred to as FD&C blue number two or just blue – and in Europe, it’s a 132.

As an indicator

  • Indigo carmine in a 0.2% aqueous solution is blue at pH 11.4 and yellow at 13.0, thus acting as a pH indicator.
  • It also serves as a redox indicator, turning yellow upon reduction.
  • Through the conversion to isatin-5-sulfonic acid, it can also be used as a dissolved ozone indicator.

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Side effects of Indigo Carmine

As Indigo Carmine is not listed in any Drug Enforcement Administration Schedules. You should be careful while swirling solutions with ICN. This dye can stain skin and clothing. To prevent spills, put a solid rubber stopper in the flask and press downward with the palm of your hand while swirling the flask, so that oxygen can be added.

It may interact with other drugs, so it is necessary to take it with a doctor’s prescription. Also, During pregnancy, the ICN drug can pass into breast milk. Consult your doctor before using it during breastfeeding.

Indigo Carmine can cause some serious side effects which include:

  1. Hives
  2. Difficulty in breathing, and
  3. Swelling of face, lips, tongue, or throat
  4. May include a mild rise in blood pressure
  5. Bronchoconstriction may occur occasionally


Where to buy Indigo Carmine?

Macsen Drugs, a unit of Macsen labs is a WHO-GMP, US-FDA and ISO-certified manufacturer and supplier of high-quality Indigo Carmine.

What is another name for Indigo Carmine?

Indigo Carmine is also known as Indigotindisulfonate sodium, 5,5’- indigodisulfonic acid sodium salt,  E132, Sicovit Indigotin 85, Food Blue 1, FD&C Blue 2, ci 73015, 4 G, C.I. Acid Blue 74, Brilliant Indigo, and Indigotine.

Is Indigo carmine FDA approved?

Indigo Carmine is not approved by FDA.

Is Indigo carmine the same as Carmine?

Indigo carmine, or 5,5-indigodisulfonic acid sodium salt, is an organic salt derived from indigo by aromatic sulfonation, which renders the compound soluble in water.

For what analysis is the indigo carmine solution used?

Indigo carmine solution, injected by the intravenous route, is used for the intra-operative analysis and detection of suspected ureteral injuries during abdominal and pelvic surgery.

How do you make indigo carmine?

Indigo Carmine is generally produced by sulfonation of natural indigo, but indigo can also be prepared synthetically by fusion of N-phenyl glycine in a mixture of sodamide and sodium and potassium hydroxides under ammonia pressure.

How do you dissolve indigo carmine?

Due to so many extra sodium ions make it is harder for the indigo carmine to dissolve and it ends up precipitating out. ICN does dissolve in water it is not that soluble, and only about a gram will dissolve in 100 ml, if at most 10 mils of water It would lose about 0.1 grams.

Why does indigo carmine turn yellow acid or base?

On top of being sensitive to pH, indigo carmine is also sensitive to oxidation and reduction, under normal conditions the ICN is in its oxidized form because it’s always in contact with oxygen in the air. ICN is pH sensitive and under strongly Basic Conditions it has a yellow-greenish colour. The ICN is in its blue form which dominates when the pH of the solution is less than about eleven points.

How does indigo carmine work as an indicator?

For this, the chemical traffic light reaction which is a nice demonstration of chemical oxidation and reduction usually takes place in a sealed container like a plastic bottle, and when it is shaken, it quickly turns red. When it’s shaken a bit more it changes to green. Even cooler though is that the reaction isn’t done yet and if it is left to sit undisturbed for a few minutes, it refers back to being red and then to yellow. It can then be shaken again to change the colour and the process can be repeated several times.

Is indigo carmine the same as methylene blue?

Methylene blue is not the same as indigo carmine. It is dominated by cells and it induces cellular DNA harm in vitro through the generation of singlet oxygen once it is photoexcited by white light. ICN seems to be photostable. It also possesses quite less potential to break genetic material in vitro. Refer here to know more.


The information provided here is based on general knowledge, articles, research publications etc and we do not claim the authenticity of any of the information provided above. We do not claim or suggest/advise any medical, therapeutic, health or nutritional benefits of Indigo Carmine. We do not supply or promote our Indigo Carmine product for the applications which are covered by valid patents and which are not approved by the FDA.

Macsen Labs is a manufacturer and supplier of several grades of Indigo Carmine such as:-



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