Zantac is used to relieve and prevent heartburn, acid indigestion, and sour stomach. The version sold today, called Zantac 360, contains famotidine, a different active ingredient than the original Zantac. It works by reducing the amount of acid your stomach produces, which eases the burning sensation in your chest and throat that comes with acid reflux.
Why Zantac Changed Its Formula
The original Zantac contained an ingredient called ranitidine. In April 2020, the FDA requested that all ranitidine products be pulled from shelves after testing revealed they contained a contaminant called NDMA, a substance classified as a probable human carcinogen. The problem wasn’t a one-time manufacturing error. FDA testing showed that NDMA levels in ranitidine increased over time, even under normal storage conditions, and rose significantly at higher temperatures. The older a ranitidine product was, the more NDMA it contained.
The Zantac brand relaunched with famotidine as its active ingredient. Famotidine belongs to the same drug class as ranitidine and works the same way, but it does not carry the NDMA contamination risk. If you see Zantac 360 on store shelves today, it’s the famotidine version.
Conditions Zantac Treats
The over-the-counter version of Zantac 360 is specifically labeled for heartburn relief and prevention. You can take it after heartburn starts, or 10 to 60 minutes before eating foods or drinking beverages that tend to trigger it.
Prescription-strength famotidine covers a broader range of conditions. Before ranitidine was removed from the market, prescription Zantac was FDA-approved for:
- Active duodenal ulcers: sores in the upper part of the small intestine, with most patients healing within four weeks
- Active gastric ulcers: sores in the stomach lining, with most patients healing within six weeks
- GERD (gastroesophageal reflux disease): chronic acid reflux where stomach acid repeatedly flows back into the esophagus
- Erosive esophagitis: damage to the esophagus caused by prolonged acid exposure
- Maintenance therapy: ongoing lower doses to prevent ulcers or esophagitis from returning after they’ve healed
- Hypersecretory conditions: rare disorders where the stomach produces far too much acid
Today, prescription famotidine fills the same roles. If your doctor prescribes it, the condition and dose will determine how long you take it.
How Zantac Reduces Stomach Acid
Zantac 360 is an H2 blocker, which refers to how it works at the cellular level. After you eat, your body releases a chemical messenger called histamine that binds to receptors on the cells lining your stomach. That binding triggers those cells to pump out acid. Famotidine attaches to those same receptors first, so the histamine signal never gets through. With the signal blocked, your stomach simply produces less acid.
This is different from antacids like Tums, which neutralize acid that’s already in your stomach. Zantac prevents the acid from being made in the first place, which is why it lasts longer and works better for recurring symptoms.
How Quickly It Works and How Long It Lasts
Famotidine begins suppressing acid production within about one hour of taking a dose. A single 20 mg tablet reduces acid output for roughly 10 to 12 hours when it comes to baseline and overnight acid secretion. For acid triggered by meals, the effect typically lasts 8 to 10 hours, though in some people a 20 mg dose may taper off after 6 to 8 hours.
This timeline is why OTC Zantac 360 can be taken preventively before a meal. If you know a spicy dinner or a glass of wine will give you trouble, taking it 10 to 60 minutes beforehand gives the drug time to start blocking acid before the food hits your stomach.
OTC Dosage
Each Zantac 360 tablet contains 20 mg of famotidine. The recommended dose for adults and children 12 and older is one tablet with a glass of water, either to relieve symptoms you’re already feeling or to prevent them before a meal. The maximum is two tablets in 24 hours, and the tablets should be swallowed whole rather than chewed.
How Zantac Compares to Stronger Acid Reducers
Proton pump inhibitors (PPIs) like omeprazole (Prilosec) and pantoprazole work differently than H2 blockers. They shut down the acid-producing pumps in your stomach cells more completely, which makes them stronger overall. In clinical trials comparing the two classes, PPIs consistently outperform H2 blockers for more serious acid-related conditions. One randomized trial found that patients on omeprazole had roughly half the rate of stomach and intestinal damage compared to those on famotidine.
That doesn’t mean Zantac is the wrong choice. For occasional heartburn, an H2 blocker often does the job with a faster onset than most PPIs, which can take one to four days to reach full effect. Zantac tends to be a better fit for people who get heartburn a few times a week and want something they can take as needed. PPIs are generally reserved for people with frequent, daily symptoms or diagnosed conditions like GERD or ulcers that need sustained acid suppression.
Side Effects
Famotidine is well tolerated by most people. The most common side effects are mild: headache, dizziness, constipation, and diarrhea. These typically don’t require medical attention unless they persist or become bothersome.
Serious reactions are uncommon but can include hives, skin rash, swelling of the face or throat, and difficulty breathing or swallowing. These are signs of an allergic reaction and need immediate attention.
Who Should Be Cautious
People with kidney disease should talk to their doctor before using famotidine, since the drug is cleared through the kidneys and may build up in the body if kidney function is reduced. The same applies if you have trouble swallowing or a condition called phenylketonuria (PKU), since some formulations contain ingredients that affect people with PKU. If you’re pregnant or breastfeeding, it’s worth discussing famotidine with your doctor before starting it, though it has not been classified as high-risk in pregnancy.
Anyone who has had an allergic reaction to famotidine or other H2 blockers like cimetidine or nizatidine should avoid Zantac 360.