Histamine h2 antagonist (oral route, injection route, intravenous route)

Brand Name

US Brand Name

Axid

Axid AR

Axid Pulvules

Heartburn Relief

Pepcid

Pepcid AC

Tagamet

Tagamet HB

Zantac

Zantac 150

Zantac 150 Efferdose

Zantac 25

Canadian Brand Name

Alti-raNITIdine

Apo-Cimetidine

Apo-Famotidine

Famotidine

Description

Histamine H2-receptor antagonists, also known as H2-blockers, are used to treat duodenal ulcers and prevent their return. They are also used to treat gastric ulcers and for some conditions, such as Zollinger-Ellison disease, in which the stomach produces too much acid. In over-the-counter (OTC) strengths, these medicines are used to relieve and/or prevent heartburn, acid indigestion, and sour stomach. H2-blockers may also be used for other conditions as determined by your doctor.

H2-blockers work by decreasing the amount of acid produced by the stomach.

H2-blockers are available both over-the-counter (OTC) and with your doctor's prescription.

Limited testing has found unacceptable levels of a probable human carcinogen, N-nitrosodimethylamine (NDMA), in some ranitidine medicines.

This product is available in the following dosage forms:

Tablet
Solution
Powder for Suspension
Capsule

Before Using

Allergies

Tell your doctor if you have ever had any unusual or allergic reaction to medicines in this group or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.

Pediatric

This medicine has been tested in children and, in effective doses, has not been shown to cause different side effects or problems than it does in adults when used for short periods of time.

Geriatric

Confusion and dizziness may be especially likely to occur in elderly patients, who are usually more sensitive than younger adults to the effects of H2-blockers.

Pregnancy

H2-blockers have not been studied in pregnant women. In animal studies, famotidine and ranitidine have not been shown to cause birth defects or other problems. However, one study in rats suggested that cimetidine may affect male sexual development. More studies are needed to confirm this. Also, studies in rabbits with very high doses have shown that nizatidine causes miscarriages and low birth weights. Make sure your doctor knows if you are pregnant or if you may become pregnant before taking H2-blockers.

Breastfeeding

Cimetidine, famotidine, nizatidine, and ranitidine pass into the breast milk and may cause unwanted effects, such as decreased amounts of stomach acid and increased excitement, in the nursing baby. It may be necessary for you to take another medicine or to stop breast-feeding during treatment. Be sure you have discussed the risks and benefits of the medicine with your doctor.

Drug Interactions

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking any of these medicines, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

Using medicines in this class with any of the following medicines is not recommended. Your doctor may decide not to treat you with a medication in this class or change some of the other medicines you take.

Bepridil
Cisapride
Dofetilide
Dronedarone
Fezolinetant
Levoketoconazole
Mesoridazine
Pimozide
Piperaquine
Saquinavir
Sparfloxacin
Terfenadine
Thioridazine
Ziprasidone

Using medicines in this class with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

Acalabrutinib
Adagrasib
Alfentanil
Alosetron
Alprazolam
Amiodarone
Amisulpride
Amphetamine
Amprenavir
Anagrelide
Apomorphine
Aprepitant
Aripiprazole
Aripiprazole Lauroxil
Arsenic Trioxide
Atazanavir
Azithromycin
Bedaquiline
Benzhydrocodone
Benzphetamine
Bosutinib
Budesonide
Buprenorphine
Bupropion
Buserelin
Capecitabine
Carbamazepine
Carmustine
Cefuroxime Axetil
Ceritinib
Chloroquine
Citalopram
Clarithromycin
Clofazimine
Clopidogrel
Clothiapine
Clozapine
Codeine
Colchicine
Crizotinib

Other Interactions

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.

Proper Use

For patients taking the nonprescription strengths of these medicines for heartburn, acid indigestion, and sour stomach:

Do not take the maximum daily dosage continuously for more than 2 weeks, unless directed to do so by your doctor.
If you have trouble in swallowing, or persistent abdominal pain, see your doctor promptly. These may be signs of a serious condition that may need different treatment.

For patients taking the prescription strengths of these medicines for more serious problems:

One dose a day—Take it at bedtime, unless otherwise directed.
Two doses a day—Take one in the morning and one at bedtime.
Several doses a day—Take them with meals and at bedtime for best results.

It may take several days before this medicine begins to relieve stomach pain. To help relieve this pain, antacids may be taken with the H2-blocker, unless your doctor has told you not to use them. However, you should wait one-half to one hour between taking the antacid and the H2-blocker. Take this medicine for the full time of treatment, even if you begin to feel better. Also, it is important that you keep your appointments with your doctor for check-ups so that your doctor will be better able to tell you when to stop taking this medicine.

For patients taking famotidine chewable tablets:

Chew the tablets well before swallowing.

For patients taking famotidine oral disintegrating tablets:

Make sure your hands are dry.
Leave tablets in unopened package until the time of use, then open the pack and remove the tablet.
Immediately place the tablet on the tongue.
The tablet will dissolve in seconds, and you may swallow it with your saliva. You do not need to drink water or other liquid to swallow the tablet.

For patients taking ranitidine effervescent tablets:

Do not chew, swallow whole or dissolve on the tongue.
Remove the foil wrapping and dissolve the 150-mg tablet in 6 to 8 ounces of water before drinking.
For infants and children: Dissolve the 25-mg tablet in no less than 5 mL (1 teaspoonful) of water in a dosing cup. Wait until the tablet is completely dissolved before administering the solution to the infant or child. You may give the medicine to your infant by dropper or oral syringe. Ask your doctor if you are unsure how much medicine to give your infant.

Dosing

The dose medicines in this class will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of these medicines. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

For cimetidine:
- For oral dosage forms (solution and tablets):
  - To treat duodenal or gastric ulcers:
    - Older adults, adults, and teenagers—300 milligrams (mg) four times a day, with meals and at bedtime. Some people may take 400 or 600 mg two times a day, on waking up and at bedtime. Others may take 800 mg at bedtime.
    - Children—20 to 40 mg per kilogram (kg) (9.1 to 18.2 mg per pound) of body weight a day, divided into four doses, taken with meals and at bedtime.
  - To prevent duodenal ulcers:
    - Older adults, adults, and teenagers—300 mg two times a day, on waking up and at bedtime. Instead some people may take 400 mg at bedtime.
    - Children—Dose must be determined by your doctor.
  - To treat heartburn, acid indigestion, and sour stomach:
    - Adults and teenagers—100 to 200 mg with water when symptoms start. The dose may be repeated once in twenty-four hours. Do not take more than 400 mg in twenty-four hours.
    - Children—Dose must be determined by your doctor.
  - To prevent heartburn, acid indigestion, and sour stomach:
    - Adults and teenagers—100 to 200 mg with water up to one hour before eating food or drinking beverages you expect to cause symptoms. Do not take more than 400 mg in twenty-four hours.
    - Children—Dose must be determined by your doctor.
  - To treat conditions in which the stomach produces too much acid:
    - Adults—300 mg four times a day, with meals and at bedtime. Your doctor may change the dose if needed.
    - Children—Dose must be determined by your doctor.
  - To treat gastroesophageal reflux disease:
    - Adults—800 to 1600 mg a day, divided into smaller doses. Treatment usually lasts for 12 weeks.
    - Children—Dose must be determined by your doctor.
- For injection dosage form:
  - To treat duodenal ulcers, gastric ulcers or conditions in which the stomach produces too much acid:
    - Older adults, adults, and teenagers—300 mg injected into muscle, every six to eight hours. Or, 300 mg injected slowly into a vein every six to eight hours. Instead, 900 mg may be injected slowly into a vein around the clock at the rate of 37.5 mg per hour. Some people may need 150 mg at first, before beginning the around-the-clock treatment.
    - Children—5 to 10 mg per kg (2.3 to 4.5 mg per pound) of body weight injected into a vein or muscle, every six to eight hours.
  - To prevent stress-related bleeding:
    - Older adults, adults, and teenagers—50 mg per hour injected slowly into a vein around the clock for up to 7 days.
    - Children—Dose must be determined by your doctor.

For famotidine:
- For oral dosage forms (suspension, tablets, chewable tablets, and oral disintegrating tablets):
  - To treat duodenal ulcers:
    - Older adults, adults, and teenagers—40 milligrams (mg) once a day at bedtime. Some people may take 20 mg two times a day.
    - Children—Dose must be determined by your doctor.
  - To prevent duodenal ulcers:
    - Older adults, adults, and teenagers—20 mg once a day at bedtime.
    - Children—Dose must be determined by your doctor.
  - To treat gastric ulcers:
    - Older adults, adults, and teenagers—40 mg once a day at bedtime.
    - Children—Dose must be determined by your doctor.
  - To treat heartburn, acid indigestion, and sour stomach:
    - Adults and teenagers—10 mg with water when symptoms start. The dose may be repeated once in twenty-four hours. Do not take more than 20 mg in twenty-four hours.
    - Children—Dose must be determined by your doctor.
  - To prevent heartburn, acid indigestion, and sour stomach:
    - Adults and teenagers—10 mg taken one hour before eating a meal you expect to cause symptoms. The dose may be repeated once in twenty-four hours. Do not take more than 20 mg in twenty-four hours.
    - Children—Dose must be determined by your doctor.
  - To treat conditions in which the stomach produces too much acid:
    - Older adults, adults, and children—20 mg every six hours. Your doctor may change the dose if needed.
    - Children—Dose must be determined by your doctor.
  - To treat gastroesophageal reflux disease:
    - Older adults, adults, and teenagers—20 mg two times a day, usually for up to 6 weeks.
    - Children weighing more than 10 kg (22 pounds)—1 to 2 mg per kilogram (kg) (0.5 to 0.9 mg per pound) of body weight a day, divided into two doses.
    - Children weighing less than 10 kg (22 pounds)—1 to 2 mg per kg (0.5 to 0.9 mg per pound) of body weight a day, divided into three doses.
- For injection dosage form:
  - To treat duodenal ulcers, gastric ulcers, or conditions in which the stomach produces too much acid:
    - Older adults, adults, and teenagers—20 mg injected into a vein, every twelve hours.
    - Children—Dose must be determined by your doctor.

For nizatidine:
- For oral dosage forms (capsules and oral solution):
  - To treat duodenal or gastric ulcers:
    - Older adults, adults, and teenagers—300 milligrams (mg) once a day at bedtime. Some people may take 150 mg two times a day.
    - Children—Dose must be determined by your doctor.
  - To prevent duodenal ulcers:
    - Adults and teenagers—150 mg once a day at bedtime.
    - Children—Dose must be determined by your doctor.
  - To prevent heartburn, acid indigestion, and sour stomach:
    - Adults and teenagers—75 mg taken thirty to sixty minutes before eating a meal you expect to cause symptoms. The dose may be repeated once in twenty-four hours.
    - Children—Dose must be determined by your doctor.
  - To treat gastroesophageal reflux disease:
    - Adults and teenagers—150 mg two times a day.
    - Children—Dose must be determined by your doctor.

For ranitidine:
- For oral dosage forms (syrup, tablets, effervescent tablets):
  - To treat active duodenal ulcers:
    - Older adults, adults, and teenagers—150 milligrams (mg) two times a day. Some people may take 300 mg once a day at bedtime.
    - Children and infants—2 to 4 mg per kilogram (kg) (1 to 2 mg per pound) of body weight twice a day. However, the total dose will not be more than 300 mg a day.
  - To maintain healing of duodenal ulcers:
    - Older adults, adults, and teenagers—150 mg once a day at bedtime.
    - Children and infants—2 to 4 mg per kg (1 to 2 mg per pound) of body weight once a day. However, the total dose will not be more than 150 mg a day.
  - To treat erosive esophagitis:
    - Older adults, adults, and teenagers—150 mg four times a day
    - Children and infants—5 to 10 mg per kg (2.3 to 4.6 mg per pound) of body weight per day, usually divided and given in two doses during the day.
  - To maintain healing of erosive esophagitis:
    - Older adults, adults, and teenagers—150 mg twice a day
    - Children and infants—Dose must be determined by your doctor.
  - To treat benign gastric ulcers:
    - Older adults, adults, and teenagers—150 mg two times a day.
    - Children and infants—2 to 4 mg per kg (1 to 2 mg per pound) of body weight twice a day. However, the total dose will not be more than 300 mg a day.
  - To maintain healing of gastric ulcers:
    - Older adults, adults, and teenagers—150 mg once a day at bedtime.
    - Children and infants—2 to 4 mg per kg (1 to 2 mg per pound) of body weight once a day. However, the total dose will not be more than 150 mg a day.
  - To treat heartburn, acid indigestion, and sour stomach:
    - Adults and teenagers—150 mg with water when symptoms start. The dose may be repeated once in twenty-four hours. Do not take more than 300 mg in twenty-four hours.
    - Children—Dose must be determined by your doctor.
  - To prevent heartburn, acid indigestion, and sour stomach:
    - Adults and teenagers—150 mg with water taken thirty to sixty minutes before eating a meal or drinking beverages you expect to cause symptoms. Do not take more than 300 mg in twenty-four hours.
    - Children—Dose must be determined by your doctor.
  - To treat some conditions in which the stomach produces too much acid:
    - Older adults, adults, and teenagers—150 mg two times a day. Your doctor may change the dose if needed.
    - Children—Dose must be determined by your doctor.
  - To treat gastroesophageal reflux disease:
    - Older adults, adults, and teenagers—150 mg two times a day. Your dose may be increased if needed.
    - Children and infants—5 to 10 mg per kg (2.3 to 4.6 mg per pound) of body weight per day, usually divided and given in two doses during the day.
- For injection dosage form:
  - To treat duodenal ulcers, gastric ulcers, or conditions in which the stomach produces too much acid:
    - Older adults, adults, and teenagers—50 milligrams (mg) injected into a muscle every six to eight hours. Or, 50 mg injected slowly into a vein every six to eight hours. Instead, you may receive 6.25 mg per hour injected slowly into a vein around the clock. However, most people will usually not need more than 400 mg a day.
  - To treat duodenal or gastric ulcers:
    - Children—2 to 4 mg per kilogram (kg) (1 to 2 mg per pound) of body weight per day, usually divided and injected slowly into a vein every six to eight hours. However the total dose will not be more than 50 mg every six to eight hours.

Missed Dose

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Storage

Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.

Keep out of the reach of children.

Do not keep outdated medicine or medicine no longer needed.

Precautions

Limited testing has found unacceptable levels of a probable human carcinogen, N-nitrosodimethylamine (NDMA), in some ranitidine medicines

Some tests may be affected by this medicine. Tell the doctor in charge that you are taking this medicine before:

You have any skin tests for allergies.
You have any tests to determine how much acid your stomach produces.

Remember that certain medicines, such as aspirin, and certain foods and drinks (e.g., citrus products, carbonated drinks) irritate the stomach and may make your problem worse.

Cigarette smoking tends to decrease the effect of H2-blockers by increasing the amount of acid produced by the stomach. This is more likely to affect the stomach's nighttime production of acid. While taking H2-blockers, stop smoking completely, or at least do not smoke after taking the last dose of the day.

Drinking alcoholic beverages while taking an H2-receptor antagonist has been reported to increase the blood levels of alcohol. You should consult your health care professional for guidance.

Check with your doctor if your ulcer pain continues or gets worse.

Side Effects

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

Rare

Abdominal pain
back, leg, or stomach pain
bleeding or crusting sores on lips
blistering, burning, redness, scaling, or tenderness of skin
blisters on palms of hands and soles of feet
changes in vision or blurred vision
confusion
coughing or difficulty in swallowing
dark-colored urine
dizziness
fainting
fast, pounding, or irregular heartbeat
fever and/or chills
flu-like symptoms
general feeling of discomfort or illness
hives
inflammation of blood vessels
joint pain
light-colored stools
mood or mental changes, including anxiety, agitation, confusion, hallucinations (seeing, hearing, or feeling things that are not there), mental depression, nervousness, or severe mental illness
muscle cramps or aches
nausea, vomiting, or loss of appetite
pain
peeling or sloughing of skin
red or irritated eyes
shortness of breath
skin rash or itching
slow heartbeat
sore throat
sores, ulcers, or white spots on lips, in mouth, or on genitals
sudden difficult breathing
swelling of face, lips, mouth, tongue, or eyelids
swelling of hands or feet
swollen or painful glands
tightness in chest
troubled breathing
unusual bleeding or bruising
unusual tiredness or weakness
unusually slow or irregular breathing
wheezing
yellow eyes or skin

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Less common or rare

Constipation
decrease in sexual desire
decreased sexual ability (especially in patients with Zollinger-Ellison disease who have received high doses of cimetidine for at least 1 year)
diarrhea
difficult urination
dizziness
drowsiness
dryness of mouth or skin
headache
increased or decreased urination
increased sweating
loss of hair
ringing or buzzing in ears
runny nose
swelling of breasts or breast soreness in females and males
trouble in sleeping

Not all of the side effects listed above have been reported for each of these medicines, but they have been reported for at least one of them. All of the H2-blockers are similar, so any of the above side effects may occur with any of these medicines.

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

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