How Fast Does Gas-X (Simethicone) Work?
In our latest question and answer, the pharmacist discusses how quickly GasX (simethicone) works.

Question
I have gastrointestinal issues and I was recommended to take Gas-X. How fast does it begin working?

Answered by Dr. Brian Staiger, PharmD
Medical Content Reviewed By HelloPharmacist
Staff
Last updated Apr 10, 2025
Key points
- Gas-X contains simethicone, which works by breaking up and reducing the formation of gas bubbles.
- Gas-X works quickly, within a few minutes of taking a dose.
Answer
Thanks so much for reaching out! Gas-X contains simethicone, an antiflatulent agent used for the symptomatic relief of flatulence (i.e. gas), gastric bloating, and postoperative gas pains.
Gas-X begins to work quickly after taking a dose by mouth, generally within a few minutes. This fast onset of action is due to how the medication works to relieve gas.
How Gas-X (Simethicone) Works
Simethicone is commonly referred to as an "anti-foaming" agent as it disperses and prevents the formation of mucus-surrounded gas pockets (i.e. bubbles) in the GI tract.
It does this by altering the surface tension of gas bubbles, preventing these pockets from forming and causing them to break apart more quickly. Simethicone allows for gas to be processed and eliminated in a more efficient manner.
As simethicone eliminates existing gas bubbles more quickly, it is sometimes used as an antifoaming agent in gastrointestinal and colonoscopy procedures
Gas-X (simethicone) is physiologically inert and is not systemically absorbed. Our bodies do not metabolize simethicone and it is excreted unchanged in the feces. Additionally, simethicone is not known to interfere with gastric secretion or nutrient absorption.
How To Take Gas-X
Gas-X is indicated to be taken up to 4 times per day after meals and at bedtime. Doses range from 40 mg to 180 per tablet (or similar dosage form).
High doses of simethicone are used for enhancing the delineation of upper abdominal anatomy in conjunction with ultrasound imaging. A specific product (SonoRx) is used for this purpose.
Additional Information
Simethicone is the anti-gas agent in several additional over-the-counter products, including some Mylanta, Phazyme and Maalox products. It typically is very well tolerated and rarely causes side effects.
Final Words
Simethicone products, such as Gas-X, work very quickly after taking a dose by mouth and you should notice relief within a few minutes.
It is important to note that you may still experience flatulence and/or belching as gas is eliminated. It should noticeably decrease bloating, however.
References
- Simethicone in the treatment of infant colic: a randomized, placebo-controlled, multicenter trial, PubMed
- Evaluation of simethicone for the treatment of postoperative abdominal discomfort in infants, PubMed
- Simethicone Monograph, ClinicalKey
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Dr. Brian Staiger, PharmD
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