Degradation of simethicone – A study on formation of D4, D5 and D6

Abstract

Simethicone, a widely used anti-foaming agent in pharmaceuticals, consists mainly of polydimethylsiloxane (PDMS) combined with silica gel. While it is safe in pharmaceutical use, concerns have been raised about its degradation into cyclic siloxanes—specifically D4, D5, and D6—which can cause environmental and health hazards. This study investigated the degradation behavior of simethicone under varying temperature and pH conditions, and examined how silica gel in the formulation influence the formation of these products. Using gas chromatography with flame ionization detection (GC-FID) for quantification and gas chromatography-mass spectrometry (GC-MS) for identification, the formation of D4, D5, and D6 was monitored under thermal and aqueous treatments. Results showed that temperature had a significant effect on degradation, with the highest levels of D4 and D5 observed around 75 °C, while pH had less impact. The presence of silica gel consistently promoted degradation, suggesting a catalytic role. Kinetic modeling indicated that the logistic model best described the generation of D4 and D5 over time. The findings highlight that simethicone can degrade into potentially harmful compounds even under mild conditions, pointing to a need for further evaluation of its long-term safety and environmental impact.

Popular Abstract

Simethicone is a common ingredient found in over-the-counter medicines used to relieve gas and bloating. It helps relieve symptoms by breaking down gas bubbles in the stomach—simple and effective. But while it’s helpful for our health, growing scientific concern suggests simethicone might not be as harmless as it seems.
Recent studies show that simethicone can degrade into some smaller compounds called D4, D5, and D6. Even though the effect for human is less severe, these substances can spread around in the environment, accumulate in animals and affecting hormone levels and even organ functions. In other words, they not only pollute nature; they may also cause health risks.
In this project, I investigated how simethicone breaks down into these risky compounds. I tested its behavior under different conditions—heat, acidity, and whether or not a component called silica gel was present. These experiments were meant to simulate what happens inside our bodies or in the environment after disposal. Using advanced chemical instruments, I measured how much of the D4, D5, and D6 compounds were formed.
The findings showed that simethicone begins to degrade even at room temperature. Higher temperatures and the presence of silica gel speed up this process. Moreover, the acidity level (pH) didn’t influence the breakdown as much as heat does. This suggests that degradation can happen quietly in ordinary conditions, not just in extreme environments.
In short, while simethicone does its job in easing stomach discomfort, it could lead to the formation of harmful compounds—ones that may affect both the environment and our health. This research helps shed light on how simethicone breaks down and points to the need for safer formulations, better disposal practices, or new ways to minimize these unwanted by-products.

• author: Pei, Yanyang
• supervisor: Peter Spégel
• organization: Centre for Analysis and Synthesis
• course: KAKM01 20251
• year: 2025
• type: H2 - Master's Degree (Two Years)
• subject: Chemistry
• keywords: simethicone, degradation, D4, D5, D6, GC-FID, analytical chemistry
• language: English
• id: 9203724
• date added to LUP: 2025-06-25 10:07:28
• date last changed: 2025-06-25 10:07:28