Dosing - The dose of histamine H 2-receptor antagonists (also called H 2-blockers) 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 number of capsules or tablets or teaspoonfuls of solution, suspension, or syrup 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 taking the H 2-receptor antagonist.

For cimetidine
For oral dosage forms (solution and tablets):
To treat duodenal or gastric ulcers:
Older adults, adults, and teenagers300 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.
Children20 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 teenagers300 mg two times a day, on waking up and at bedtime. Instead some people may take 400 mg at bedtime.
ChildrenDose must be determined by your doctor.
To treat heartburn, acid indigestion, and sour stomach:
Adults and teenagers100 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.
ChildrenDose must be determined by your doctor.
To prevent heartburn, acid indigestion, and sour stomach:
Adults and teenagers100 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.
ChildrenDose must be determined by your doctor.
To treat conditions in which the stomach produces too much acid:
Adults300 mg four times a day, with meals and at bedtime. Your doctor may change the dose if needed.
ChildrenDose must be determined by your doctor.
To treat gastroesophageal reflux disease:
Adults800 to 1600 mg a day, divided into smaller doses. Treatment usually lasts for 12 weeks.
ChildrenDose must be determined by your doctor.
For injectable dosage form:
To treat duodenal ulcers, gastric ulcers or conditions in which the stomach produces too much acid:
Older adults, adults, and teenagers300 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.
Children5 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 teenagers50 mg per hour injected slowly into a vein around the clock for up to 7 days.
ChildrenDose 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 teenagers40 milligrams (mg) once a day at bedtime. Some people may take 20 mg two times day.
ChildrenDose must be determined by your doctor.
To prevent duodenal ulcers:
Older adults, adults, and teenagers20 mg once a day at bedtime.
ChildrenDose must be determined by your doctor.
To treat gastric ulcers:
Older adults, adults, and teenagers40 mg once a day at bedtime.
ChildrenDose must be determined by your doctor.
To treat heartburn, acid indigestion, and sour stomach:
Adults and teenagers10 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.
ChildrenDose must be determined by your doctor.
To prevent heartburn, acid indigestion, and sour stomach:
Adults and teenagers10 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.
ChildrenDose must be determined by your doctor.
To treat conditions in which the stomach produces too much acid:
Older adults, adults, and children20 mg every six hours. Your doctor may change the dose if needed.
ChildrenDose must be determined by your doctor.
To treat gastroesophageal reflux disease:
Older adults, adults, and teenagers20 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 injectable dosage form:
To treat duodenal ulcers, gastric ulcers, or conditions in which the stomach produces too much acid:
Older adults, adults, and teenagers20 mg injected into a vein, every twelve hours.
ChildrenDose must be determined by your doctor.
For nizatidine
For oral dosage forms (capsules and tablets):
To treat duodenal or gastric ulcers:
Older adults, adults, and teenagers300 milligrams (mg) once a day at bedtime. Some people may take 150 mg two times a day.
ChildrenDose must be determined by your doctor.
To prevent duodenal ulcers:
Adults and teenagers150 mg once a day at bedtime.
ChildrenDose must be determined by your doctor.
To prevent heartburn, acid indigestion, and sour stomach:
Adults and teenagers75 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.
ChildrenDose must be determined by your doctor.
To treat gastroesophageal reflux disease:
Adults and teenagers150 mg two times a day.
ChildrenDose must be determined by your doctor.
For ranitidine
For oral dosage forms ( effervescent granules, syrup, tablets, effervescent tablets):
To treat duodenal ulcers:
Older adults, adults, and teenagers150 milligrams (mg) two times a day. Some people may take 300 mg once a day at bedtime.
Children2 to 4 mg per kilogram (kg) (1 to 2 mg per pound) of body weight per day, usually given as two divided doses. .However, your total dose will not be more than 300 mg a day.
To prevent duodenal ulcers:
Older adults, adults, and teenagers150 mg at bedtime.
ChildrenDose must be determined by your doctor.
To treat gastric ulcers:
Older adults, adults, and teenagers150 mg two times a day.
Children2 to 4 mg per kilogram (1 to 2 mg per pound) of body weight per day, usually given as two divided doses. However, your total dose will not be more than 300 mg a day.
To treat heartburn, acid indigestion, and sour stomach:
Adults and teenagers75 mg with water when symptoms start. The dose may be repeated once in twenty-four hours. Do not take more than 150 mg in twenty-four hours.
ChildrenDose must be determined by your doctor.
To prevent heartburn, acid indigestion, and sour stomach:
Adults and teenagers75 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 150 mg in twenty-four hours.
ChildrenDose must be determined by your doctor.
To treat some conditions in which the stomach produces too much acid:
Older adults, adults, and teenagers150 mg two times a day. Your doctor may change the dose if needed.
ChildrenDose must be determined by your doctor.
To treat gastroesophageal reflux disease:
Older adults, adults, and teenagers150 mg two times a day. Your dose may be increased if needed.
Children5 to 10 mg per kg (2.3 to 4.6 mg per pound) of body weight a day, usually divided and given in two doses during the day. However, most children usually will not take more than 300 mg a day.
For injectable dosage form:
To treat duodenal ulcers, gastric ulcers, or conditions in which the stomach produces too much acid:
Older adults, adults, and teenagers50 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:
Children2 to 4 mg per kg (1 to 2 mg per pound) of body weight a day, injected slowly into a vein.

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 - To store this medicine:

Keep out of the reach of children.
Store away from heat and direct light.
Do not store the capsule or tablet form of this medicine in the bathroom, near the kitchen sink, or in other damp places. Heat or moisture may cause the medicine to break down.
Keep the liquid form of this medicine from freezing.
Do not keep outdated medicine or medicine no longer needed. Be sure that any discarded medicine is out of the reach of children.

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