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Xanthan gum is a cream-to-white-colored, odorless, free-flowing fine powder. As a natural polymeric compound, it dissolves in water to form a translucent, viscous solution but remains insoluble in organic solvents like ethanol, isopropanol, and acetone. Its aqueous solutions exhibit excellent thickening properties and remarkable stability within a temperature range of -4 to 80°C. However, precipitation occurs when the concentration of ethanol, isopropanol, or acetone in water exceeds 50-60%. Xanthan gum also demonstrates strong resistance to acids, alkalis, and enzymatic degradation. The viscosity of its solutions remains unaffected by pH values ranging from 1.5 to 13.

Xanthan gum is a polysaccharide produced by a pure-culture aerobic fermentation of a carbohydrate with Xanthomonas campestris. The polysaccharide is then purified by recovery with propan-2-ol, dried, and milled.

Rhodigel (Vanderbilt).

Xanthan gum is widely used in oral and topical pharmaceutical formulations, cosmetics, and foods as a suspending and stabilizing agent. It is also used as a thickening and emulsifying agent. It is nontoxic, compatible with most other pharmaceutical ingredients, and has good stability and viscosity properties over a wide pH and temperature range. Xanthan gum gels show pseudoplastic behavior, the shear thinning being directly proportional to the shear rate. The viscosity returns to normal immediately on release of shear stress.
Xanthan gum has been used as a suspending agent for conventional, dry and sustained-release suspensions. When xanthan gum is mixed with certain inorganic suspending agents, such as magnesium aluminum silicate, or organic gums, synergistic rheological effects occur. In general, mixtures of xanthan gum and magnesium aluminum silicate in ratios between 1 : 2 and 1 : 9 produce the optimum properties. Similarly, optimum synergistic effects are obtained with xanthan gum : guar gum ratios between 3 : 7 and 1 : 9.
Although primarily used as a suspending agent, xanthan gum has also been used to prepare sustained-release matrix tablets. Controlled-release tablets of diltiazem hydrochloride prepared using xanthan gum have been reported to sustain the drug release in a predictable manner, and the drug release profiles of these tablets were not affected by pH and agitation rate. Xanthan gum has also been used to produce directly compressed matrices that display a high degree of swelling due to water uptake, and a small amount of erosion due to polymer relaxation. It has also been used in combination with chitosan, guar gum, galactomannan, and sodium alginate to prepare sustained-release matrix tablets. Xanthan gum has been used as a binder, and in combination with Konjac glucomannan is used as an excipient for controlled colonic drug delivery. Xanthan gum with boswellia (3 : 1) and guar gum (10 : 20) have shown the best release profiles for the colon-specific compression coated systems of 5- fluorouracil for the treatment of colorectal cancer. Xanthan gum has also been used with guar gum for the development of a floating drug delivery system.It has also has derivatized to sodium carboxymethyl xanthan gum and crosslinked with aluminum ions to prepare microparticles, as a carrier for protein delivery. Xanthan gum has been incorporated in an ophthalmic liquid dosage form, which interacts with mucin, thereby helping in the prolonged retention of the dosage form in the precorneal area. When added to liquid ophthalmics, xanthan gum delays the release of active substances, increasing the therapeutic activity of the pharmaceutical formulations.
Xanthan gum can be used to increase the bioadhesive strength in vaginal formulations. Xanthan gum alone or with carbopol 974P has been used as a mucoadhesive controlled-release excipient for buccal drug delivery. Modified xanthan films have been used as a matrix system for transdermal delivery of atenolol. Xanthan gum has also been used as a gelling agent for topical formulations incorporating solid lipid nanoparticles of vitamin A or microemulsion of ibuprofen. A combined polymer system consisting of xanthan gum, carboxy methylcellulose and a polyvinyl pyrolidone backboned polymer has been used for relieving the symptoms of xerostomia. Xanthan gum can also be used as an excipient for spray-drying and freeze-drying processes for better results. It has been successfully used alone or in combination with agar for microbial culture media.
Xanthan gum is also used as a hydrocolloid in the food industry, and in cosmetics it has been used as a thickening agent in shampoo. Polyphosphate with xanthum gum in soft drinks is suggested to be effective at reducing erosion of enamel

Xanthan gum is widely used in oral and topical pharmaceutical formulations, cosmetics, and food products, and is generally regarded as nontoxic and nonirritant at the levels employed as a pharmaceutical excipient.
The estimated acceptable daily intake for xanthan gum has been set by the WHO at up to 10 mg/kg body-weight.
No eye or skin irritation has been observed in rabbits and no skin allergy has been observed in guinea pigs following skin exposure. No adverse effects were observed in long term feeding studies with rats (up to 1000 mg/kg/day) and dogs (up to 1000 mg/kg/day). No adverse effects were observed in a three-generation reproduction study with rats (up to 500 mg/kg/day).
LD50 (dog, oral): >20 g/kg
LD50 (rat, oral): >45 g/kg
LD50 (mouse, oral): >1 g/kg
LD50 (mouse, IP): >50 mg/kg
LD50 (mouse, IV): 100–250 mg/kg

Xanthan gum is a stable material. Aqueous solutions are stable over a wide pH range (pH 3–12), although they demonstrate maximum stability at pH 4–10 and temperatures of 10–60°C. Xanthan gum solutions of less than 1% w/v concentration may be adversely affected by higher than ambient temperatures: for example, viscosity is reduced. Xanthan gum provides the same thickening, stabilizing, and suspending properties during long-term storage at elevated temperatures as it does at ambient conditions. In addition, it ensures excellent freeze–thaw stability. Solutions are also stable in the presence of enzymes, salts, acids, and bases. Vanzan NF-ST is especially designed for use in systems containing high salt concentrations as it dissolves directly in salt solutions, and its viscosity is relatively unaffected by high salt levels as compared with general purpose grades.
The bulk material should be stored in a well-closed container in a cool, dry place.

Xanthan gum is an anionic material and is not usually compatible with cationic surfactants, polymers, or preservatives, as precipitation occurs. Anionic and amphoteric surfactants at concentrations above 15% w/v cause precipitation of xanthan gum from a solution.
Under highly alkaline conditions, polyvalent metal ions such as calcium cause gelation or precipitation; this may be inhibited by the addition of a glucoheptonate sequestrant. The presence of low levels of borates (<300 ppm) can also cause gelation. This may be avoided by increasing the boron ion concentration or by lowering the pH of a formulation to less than pH 5. The addition of ethylene glycol, sorbitol, or mannitol may also prevent this gelation.
Xanthan gum is compatible with most synthetic and natural viscosity-increasing agents, many strong mineral acids, and up to 30% inorganic salts. If it is to be combined with cellulose derivatives, then xanthan gum free of cellulase should be used to prevent depolymerization of the cellulose derivative. Xanthan gum solutions are stable in the presence of up to 60% water-miscible organic solvents such as acetone, methanol, ethanol, or propan-2- ol. However, above this concentration precipitation or gelation occurs.
The viscosity of xanthan gum solutions is considerably increased, or gelation occurs, in the presence of some materials such as ceratonia, guar gum, and magnesium aluminum silicate. This effect is most pronounced in deionized water and is reduced by the presence of salt. This interaction may be desirable in some instances and can be exploited to reduce the amount of xanthan gum used in a formulation.
Xanthan gum is incompatible with oxidizing agents, some tablet film-coatings, carboxymethylcellulose sodium, dried aluminum hydroxide gel, and some active ingredients such as amitriptyline, tamoxifen, and verapamil.

GRAS listed. Accepted for use as a food additive in Europe. Included in the FDA Inactive Ingredients Database (oral solutions, suspensions, and tablets; rectal and topical preparations). Included in nonparenteral medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.