Cimetidine (Tagamet HB) and Mylanta Maximum Strength (aluminum hydroxide/magnesium hydroxide/simethicone) are both used to treat heartburn and related stomach issues. However, they belong to different medication classes. Cimetidine is a histamine H2 receptor antagonist (H2RA) that reduces stomach acid production, while Mylanta Maximum Strength is a combination of antacids and an antiflatulent that neutralizes stomach acid and relieves gas. Both medications are available over-the-counter and come as an oral liquid, but cimetidine also comes as an oral tablet. Cimetidine can be used for conditions like GERD and ulcers, while Mylanta Maximum Strength is for short-term relief of heartburn, sour stomach, indigestion, and gas. Cimetidine may cause side effects like headache and dizziness and has many drug interactions. Mylanta Maximum Strength can cause diarrhea and nausea and may not be suitable for people with kidney problems. Cimetidine may sometimes be used off-label for molluscum contagiosum.