In April 2020, the Food and Drug Administration (FDA) requested that all forms of prescription and over-the-counter (OTC) ranitidine (Zantac) be removed from the U.S. market. They made this recommendation because unacceptable levels of NDMA, a probable carcinogen (or cancer-causing chemical), were present in some ranitidine products. People taking prescription ranitidine should talk with their doctor about safe alternative options before stopping the drug. People taking OTC ranitidine should stop taking the drug and talk with their healthcare provider about alternative options. Instead of taking unused ranitidine products to a drug take-back site, a person should dispose of them according to the product’s instructions or by following the FDA’s guidance.

H2 blockers are sometimes called H2 receptor antagonists, or H2RAs. They reduce the amount of acid that the stomach produces.

Reducing the production of stomach acid can help treat many health conditions, including gastroesophageal reflux disease (GERD), gastric ulcers, and occasional heartburn.

In the 1980s, H2 blockers were the treatment of choice for many acid-related stomach conditions. Doctors may now recommend other treatments.

Keep reading to learn more about the types of H2 blockers, their uses, and some possible side effects.

A chemical called histamine stimulates cells in the stomach lining to make hydrochloric acid. Too much of this acid can cause GERD and other painful conditions.

H2 blockers bind to histamine receptors in the stomach, reducing the amount of acid that the stomach lining secretes. This helps relieve symptoms of an overproduction of stomach acid.

This type of drug usually offers relief within 60 minutes, and the effects can last 4–10 hours.

H2 blockers can treat or prevent a number of health problems, including:

  • heartburn
  • GERD
  • duodenal and gastric ulcers
  • upper gastrointestinal bleeding
  • gastric hypersecretory diseases, such as Zollinger-Ellison syndrome

The FDA has approved the use of the three H2 blockers. Below, we describe the generic and branded forms:

Cimetidine

Cimetidine (Tagamet, Leader Heartburn Relief) comes in prescription, OTC, injectable, and IV forms. A doctor can advise about the most effective type for each person.

It is important to follow directions for use carefully. The right dosage depends on a person’s age, whether they are taking any other medications, and the form of the drug.

Older adults should avoid taking this medication, or use it with extreme caution. It may worsen or cause periods of confusion.

People with kidney or liver disease should consult a doctor before using Tagamet. Some common side effects include:

  • headaches
  • drowsiness
  • joint or muscle pain
  • breast swelling and tenderness, in anyone
  • dizziness
  • confusion in elderly people, people with dementia, and those who are critically ill

In some cases, people may also experience:

  • a rash
  • an allergic reaction
  • production of breast milk
  • trouble urinating
  • pancreatitis
  • a kidney infection

Nizatidine

Nizatidine (Axid, Tazac) comes as an oral solution or capsule.

The right dosage depends on a person’s age, their symptoms, and the form of the drug. A person should consult a doctor before taking it.

Like other H2 blockers, this medication may not be suitable for people with disorders of the kidneys or liver. A doctor or another healthcare professional can offer specific guidance.

Some common side effects include:

  • congestion, a runny nose, and similar symptoms, which are more common with Axid than with other H2 blockers
  • a rash
  • drowsiness
  • irritability
  • anxiety
  • vomiting
  • diarrhea
  • a fever

On rare occasions, a person may experience more serious side effects, including:

  • hepatitis
  • anemia
  • jaundice
  • chest pain
  • impotence
  • seizures
  • a rapid heart rate
  • a severe allergic reaction

Famotidine

Famotidine (Fluxid, Pepcid) comes in prescription and nonprescription oral formulas and as an IV infusion.

A doctor or another healthcare professional can recommend the right dosage, based on the person’s symptoms, age, kidney function, and overall health.

Side effects can include:

  • diarrhea
  • dizziness
  • nausea
  • a loss of appetite

Rarely, people experience more severe side effects, including:

  • conjunctivitis, also called pink eye
  • hepatitis
  • depression
  • confusion
  • seizures
  • severe allergic reactions
  • Stevens-Johnson syndrome, a potentially life threatening skin disorder

For the best results, a person should take H2 blockers orally once a day. The best time to take a daily dose of H2 blockers is before bed.

If a person takes the more common twice daily doses of H2 blockers, they should take the first dose in the morning and the second dose in the evening.

All four approved H2 blockers pass into breast milk, and researchers have yet to determine whether they are safe for pregnant or nursing people to take. A doctor can provide more specific guidance.

H2 blockers can also interact with other drugs. For example, Tagamet may alter the effectiveness of some pain relief medications. It may also reduce the body’s metabolism of warfarin, a blood thinner.

These drugs can affect the body’s ability to absorb vitamin B12, vitamin D, folate, and some other nutrients. In addition, people who take H2 blockers and magnesium supplements should do so at different times of day to reduce the risk of interactions.

Overall, anyone considering taking an H2 blocker should consult a healthcare professional first. These drugs are typically considered safe — only about 3% of people who take them experience serious side effects.

Depending on the health condition, a doctor may recommend a more effective treatment. For example, antibiotics are more effective at treating ulcers that result from infection with Helicobacter pylori bacteria.

Some people who take H2 blockers have a higher risk of some central nervous system side effects. These include people:

  • over the age of 50
  • with kidney problems
  • with hepatic impairment

These people, in particular, should speak with a doctor before taking H2 blockers.

Central nervous system side effects include delirium, confusion, hallucinations, and slurred speech.

H2 blockers can also pass into breast milk, so anyone who is or may soon be breastfeeding should speak with a doctor before taking the medication.

These drugs can also interact with other medications. Tagamet, for example, can alter how effective some pain relief medications are. If a person is taking medication for severe pain, then they may wish to discuss this with a doctor before taking Tagamet.

Tagamet may also reduce the effect of the blood thinner warfarin. Anyone taking warfarin should discuss this risk with a doctor.

A number of other options may help, including:

Lifestyle changes

Some helpful self-care strategies include:

  • Losing weight: For anyone with obesity or overweight, reaching and maintaining a moderate weight can reduce symptoms of an overproduction of stomach acid.
  • Quitting smoking: Avoiding secondhand smoke, and quitting smoking, if this applies, can help symptoms improve.
  • Elevating the head more in bed: Having the head raised 6–8 inches above the mattress, with a foam wedge or an extra pillow, can help ease symptoms.
  • Dietary adjustments: Certain foods and drinks can trigger GERD symptoms or make them worse. A person might try avoiding acidic, high fat, and spicy foods, alcoholic drinks, chocolate, coffee, and mint, for example.

Antacids

Antacids are OTC medications that neutralize stomach acid. They can relieve mild symptoms of an overproduction of stomach acid, but a person should receive professional guidance and treatment for more severe symptoms.

Common antacid brands include Alka-Seltzer, Gaviscon, and TUMS. Side effects can include diarrhea and constipation.

Proton pump inhibitors

Proton pump inhibitors work by reducing the amount of acid that the stomach makes. These drugs may be a more effective treatment for high acid levels than H2 blockers. These drugs can treat heartburn, acid reflux, GERD, and stomach ulcers.

Side effects are not common, but they may include headaches, diarrhea, and an upset stomach.

GERD, stomach ulcers, and other health conditions can cause the body to produce high levels of stomach acid. This can cause stomach pain and other symptoms.

H2 blockers are an effective treatment. They bind to histamine receptors in the stomach, reducing the amount of acid that the stomach lining secretes.

Various H2 blockers are available, but they can cause unwanted side effects. A person should speak to a doctor before starting this treatment.

Effective self-care strategies include dietary changes, avoiding smoke and smoking, elevating the head more during sleep, and weight loss, for people with overweight or obesity.

In terms of medication, some alternatives to H2 blockers are antacids and proton pump inhibitors.