Does simethicone lose effectiveness if taken regularly? does it have any bad side effects?

Well tolerated ..: Overall it has limited adverse effects besides some reports of loose stool and stomach upset. It works as a "surfactant" to alter gas bubble formation, so it does not necessarily loose effective over time, just like soap! If you need to take it regular review this with your doctor because there may be a better way to address your symptoms. Best of luck.