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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
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.
- Dofetilide
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.
- Alosetron
- Atazanavir
- Carmustine
- Chloroquine
- Dasatinib
- Delavirdine
- Meperidine
- Metformin
- Morphine
- Morphine Sulfate Liposome
- Posaconazole
- Theophylline
- Tizanidine
- Tolazoline
- Zalcitabine
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. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Other Medical Problems
The presence of other medical problems may affect the use of medicines in this class. Make sure you tell your doctor if you have any other medical problems, especially:
- Kidney disease or
- Liver disease—The H2-blocker may build up in the bloodstream, which may increase the risk of side effects.
- Phenylketonuria (PKU)—Some H2-blockers contain aspartame. Aspartame is converted to phenylalanine in the body and must be used with caution in patients with PKU. The Pepcid AC brand of famotidine chewable tablets contains 1.4 mg of phenylalanine per 10-mg dose. The Pepcid RPD brand of famotidine oral dispersible tablets contains 1.05 mg of phenylalanine per 20-mg dose. The Zantac brand of ranitidine EFFERdose tablets contains 2.81 mg of phenylalanine per 25-mg dose and 16.84 mg of phenylalanine per 150-mg dose.
- Porphyria (rare family disease that affects the way your body digests food)—May make condition worse in patients who have acute porphyria
- Weakened immune system (difficulty fighting infection)—Decrease in stomach acid caused by H2-blockers may increase the possibility of a certain type of infection
