VA Class:GA900

AHFS Class:

• Antiflatulents 56:10

Generic Name(s):

• Simethicone

Simethicone, a mixture of fully methylated linear siloxane polymers, is an antiflatulent secondary to its antifoam properties.

Flatulence, Functional Gastric Bloating, and Postoperative Gas Pains

Simethicone is used as an adjunct in the symptomatic treatment of flatulence, functional gastric bloating, and postoperative gas pains. For self-medication , the drug is used as an antiflatulent to relieve symptoms commonly referred to as gas, including upper GI bloating, pressure, fullness, or stuffed feeling.102,  103,  104,  105 Simethicone also has been used prior to gastroscopy to enhance visualization and prior to radiography of the intestine to reduce gas shadows. Although there is gastroscopic evidence that simethicone aids in the elimination of gas from the GI tract and reduces postoperative gas pains, the relationship of gas accumulation to what patients commonly refer to as symptoms of gas under ordinary conditions is not clear; however, the drug also has been shown to be effective in relieving these symptoms. Preparations of simethicone with antacids, antispasmodics, or digestive enzymes are available, but use of inflexible combinations of drugs is often unwarranted, and these products have not been well evaluated.

Immediate Postprandial Upper Abdominal Distress

Although simethicone is an effective antiflatulent,101,  102,  103,  104,  105 there currently is no conclusive evidence that immediate postprandial upper abdominal distress (IPPUAD) is caused by excessive gas, despite the fact that many patients commonly attribute symptoms of the distress to gas.100,  101 In addition, current data are insufficient to establish the efficacy of simethicone for the symptomatic relief of IPPUAD, a symptom complex that occurs within 30 minutes after a meal and consists of sensations of GI bloating, distention, fullness, or pressure with upper abdominal discomfort but not aerophagia or hyperacidity.101,  102

Intestinal Distress

There currently is no conclusive data that gas is responsible for any of the symptoms of intestinal distress, a self-limiting syndrome that is not attributable to any organic cause and that consists of abdominal discomfort (bloating, distention, fullness, pressure, pain, and/or cramps) occurring within 30 minutes to several hours after a meal but that is not accompanied by diarrhea or constipation.100,  101 Current data also are insufficient to establish the efficacy of simethicone for symptomatic relief of intestinal distress.100,  101

Administration

Simethicone is administered orally. Simethicone chewable tablets should be chewed thoroughly before swallowing. Simethicone liquid-filled capsules should not be chewed.

Dosage

The usual dosage of simethicone for adults and children older than 12 years of age is 40-125 mg 4 times daily after meals and at bedtime. The drug also may be taken as necessary or as directed by a physician; higher than usual dosages have been used. For self-medication, total dosage should not exceed 500 mg daily. A simethicone dosage of 20 mg 4 times daily after meals and at bedtime (with a maximum dosage for self-medication of 120 mg daily) is recommended for children younger than 2 years of age, and a dosage of 40 mg 4 times daily after meals and at bedtime (with a maximum dosage for self-medication of 240 mg daily) is recommended for children 2-12 years of age.

Prior to gastroscopy or radiography of the intestine, adults have been given a single dose of 67 mg of simethicone as the oral suspension, in 2.5 mL of water.

Simethicone is apparently nontoxic, and no adverse effects have been reported. Simethicone is not recommended for the treatment of infant colic because of limited information on its safety in infants and children.

Pharmacology

The clinical use of simethicone is based on its antifoam properties. Silicone antifoams spread on the surface of aqueous liquids, forming a film of low surface tension and thus causing collapse of foam bubbles. Simethicone reportedly allows mucus-surrounded gas bubbles in the GI tract to coalesce and be expelled.

Pharmacokinetics

Simethicone is physiologically inert; it does not appear to be absorbed from the GI tract or to interfere with gastric secretion or absorption of nutrients. Following oral administration, the drug is excreted unchanged in feces.

Chemistry and Stability

Chemistry

Simethicone is a mixture of fully methylated linear siloxane polymers containing repeating units of polydimethylsiloxane, stabilized with trimethylsiloxy end-blocking units, and silicon dioxide. Simethicone contains 90.5-99% of polydimethylsiloxane and 4-7% silicon dioxide. Polydimethylsiloxanes are practically inert polymers; those present in simethicone have a molecular weight of 14,000-21,000. The mixture is a gray, translucent, viscous fluid. Simethicone is insoluble in water and in alcohol. The liquid phase is soluble in chloroform, ether, or benzene, but silicon dioxide remains as a residue in these solvents. Simethicone oral suspension is a suspension of simethicone in water.

Stability

Simethicone tablets and chewable tablets should be stored in well-closed containers at a temperature less than 40°C, preferably between 15-30°C. Simethicone oral suspension should be stored in tight, light-resistant containers at a temperature less than 40°C, preferably between 15-30°C; freezing should be avoided.

Only references cited for selected revisions after 1984 are available electronically.

100. Food and Drug Administration. Digestive aid products for over-the-counter human use; establishment of a monograph. [21 CFR Part 357; Docket No. 81N-0106] Fed Regist . 1982; 47:454-87.

101. Food and Drug Administration. Digestive aid products for over-the-counter human use; tentative final monograph. [21 CFR Part 357; Docket No. 81N-0106] Fed Regist . 1988; 53:2706-14. (IDIS 240339)

102. Food and Drug Administration. Antiflatulent drug products for over-the-counter human use; proposed amendment of monograph. [21 CFR Part 332; Docket No. 87N-0053] Fed Regist . 1988; 53:2716-7. (IDIS 240340)

103. Food and Drug Administration. Over-the-counter drugs: proposal establishing a monograph for antacid products. [21 CFR Part 130] Fed Regist . 1973; 38:8714-24.

104. Food and Drug Administration. Over-the-counter drugs generally recognized as safe and effective and not misbranded: tentative final order for antacid products. [21 CFR Part 130] Fed Regist . 1973; 38:31258-69.

105. Food and Drug Administration. Antacid products for over-the-counter (OTC) human use. Antiflatulent products for over-the-counter (OTC) human use. Final order for antacid and antiflatulent products generally recognized as safe and effective and not misbranded. [21 CFR Parts 331 and 332] Fed Regist . 1974; 39:19862-77.