The maximum dosage of simethicone, the active ingredient in Gas-X, for adults and teenagers is 500 milligrams in 24 hours, states Drugs.com. A doctor should determine the appropriate dosage for children. Gas-X extra-strength softgels contain 125 milligrams of simethicone, according to DailyMed. Gas-X regular-strength chewables contain 80 milligrams each.
Taking simethicone after meals and at bedtime maximizes its effectiveness, and thoroughly chewing the chewable tablets helps the medicine work faster, states Drugs.com.
Other medications for gas relief that use simethicone include Alka-Seltzer Anti-Gas, Baby Gasz, Maalox Anti-Gas and Mylanta Gas, notes Drugs.com. These medications are available in chewable tablets, capsules, liquids and suspensions.