Simethicone Excipient | Uses, Suppliers, and Specifications
Simethicone as a mixture of fully methylated linear siloxane polymers containing repeating units of the formula stabilized with trimethylsiloxy end blocking units of the formula and silicon dioxide. It contains not less than 9-.5% and not more than 99.0% of the polydimethylsiloxane and not less than 4.0% and more than 7.0% of silicon dioxide. The PhEur 6.0 additionally states that the degree of polymerization is between 20-400.
Simethicone occurs as a translucent, gray-colored, viscous fluid.
Physicochemical Properties
| Physical state | Viscous grey liquid |
| Boiling point | 35 oC |
| Defoaming performance | < 5 s (at 20 ppm) |
| Volatility, 15g, 4hr, 200 oC | < 1% |
| Refractive index | n = 0.965 – 1.410 |
| Solubility | Practically insoluble in ethanol (95%) and water. The liquid phase is soluble in other silicone fluids, but silicon dioxide remains as a residue |
| Specific gravity | 0.95—0.98 at 25 oC |
| Viscosity (kinematic) | 37OcSt at 25 C for Dow Corning Q7-2243 LVA. |
Applications in Pharmaceutical Formulations
Simethicone is an antifoaming agent; tablet diluent and water-repelling agent. It’s main use is as an excipient where it functions as an antifoaming agent in pharmaceutical manufacturing processes, for which 1-50 ppm is used.
Therapeutically, simethicone is included in a number of oral pharmaceutical formulations as an antiflatulent, although its therapeutic benefit is questionable. It is also included in antacid products such as tablets or capsules. In some types of surgical or gastroscopic procedures where gas is used to inflate the body cavity, a defoaming preparation containing simethicone may be used in the area to control foaming of the fluids.
When simethicone is used in aqueous formulations, it should be emulsified to ensure compatibility with the aqueous system and components.
In the USA, up to 10 ppm of simethicone may be used in food products.
Pharmacopoeial Specifications
| Test | Specification | Reference |
| Identification | A, B, C | USP-NF/PhEur |
| Appearance | Viscous, greyish white, opalescent liquid | USP-NF/PhEur |
| Production | Polydimethylsiloxane is obtained by hydrolysis and polycondensation of dicloromethane with a degree of polymerization between 200 and 400 | USP-NF/ PhEur |
| Acidity | ≤ 3.0 ml 0.01 M NaOH | USP-NF/PhEur |
| Defoaming activity | ≤ 15 s | USP-NF/PhEur |
| Loss on heating | ≤ 18% | USP-NF/PhEur |
| Volatile matter | ≤ 1.0% | USP-NF/PhEur |
| Heavy metals | ≤5 ppm | USP-NF/PhEur |
| Mineral oils | + | USP-NF/PhEur |
| Phenylated compounds | + | USP-NF/PhEur |
| Assay (dimethicone) | + | USP-NF/PhEur |
| Assay (silica) | + | USP-NF/PhEur |
| Assay (polydimethylsiloxane) | + | USP-NF/PhEur |
Safety and Regulatory Status
Simethicone is listed in all the major pharmacopoeia. It is also GRAS listed and included in the FDA Inactive Ingredients Database (oral emulsions, powders, solutions, suspensions, tablets; and rectal and topical preparations).
Simethicone is used in cosmetics, foods, and oral and topical pharmaceutical formulations, and is generally regarded as a relatively nontoxic and non-irritant material when used as an excipient. Direct contact with the eye may cause irritation.
Therapeutically, oral doses of 125-250mg of simethicone, three or four times daily, have been given as an antiflatulent. Doses of 20-40mg of simerthicone have been given with feeds to relieve colic in infants.
LD50 (dog, IV): O.9g/kg
Stability and Storage Conditions
Simethicone is generally regarded as a stable material when stored in the original unopened container. A shelf-life of 18 months from the date of manufacture is typical. However, some simethicone products have a tendency for the silicon dioxide to settle slightly and containers of simethicone should therefore be shaken thoroughly to ensure uniformity of contents before sampling or use. Simethicone should be stored in a cool, dry, location away from oxidizing materials.
Simethicone can be sterilized by dry heating or autoclaving. With dry heating, a minimum of 4 hours at 160 oC is required.
Simethicone as supplied is not generally compatible with aqueous systems and will float like an oil on a formulation unless it is first emulsified. It should not be used in formulations or processing conditions that are very acidic (below pH 3) or highly alkaline (above pH 10), since these conditions may have some tendency to break the polydimethylsiloxane polymer. Simethicone cannot normally be mixed with polar solvents of any kind because it is very minimally soluble. Simethicone is incompatible with oxidizing agents.
Handling Precautions
Observe normal precautions appropriate to the circumstances and quantity of material handled. Eye protection and gloves are recommended. Simethicone should be handled in areas with adequate ventilation.
References
[1] T.J. Metcalf, T.G. Irons, L.D. Sher, P.C. Young, Simethicone in the treatment of infant colic: a randomized, placebo-controlled, multicenter trial, Pediatrics, 94 (1994) 29-34.
[2] C. Séné, D. Neun, L. Tan-Sien-Hee, K. Ulman, Silicones as Excipients for Topical Pharmaceutical Applications The Silky Touch Product Family from Dow Corning, Dow Corning Corp, (2002).
[3] M. Gripp, C. Schuijt, USE OF SIMETHICONE IN CONSTIPATED PATIENTS, 2005.
[4] L. Wu, Y. Cao, C. Liao, J. Huang, F. Gao, Systematic review and meta-analysis of randomized controlled trials of Simethicone for gastrointestinal endoscopic visibility, Scandinavian Journal of Gastroenterology, 46 (2011) 227-235.
PRODUCT SUMMARY
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