How does this medication work? What will it do for me?

Cimetidine is used to reduce the pain of ulcer and heartburn or to assist in the healing of ulcers and damage caused by gastroesophageal reflux disease (GERD).

Cimetidine is also used to prevent ulcers in certain circumstances and to treat certain conditions that are associated with oversecretion of acid by the stomach (i.e., Zollinger-Ellison Syndrome, systemic mastocytosis, and multiple endocrine adenomas). The medication works by reducing the amount of acid secreted by the stomach.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. As well, some forms of this medication may not be used for all of the conditions discussed here. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

This medication is available as 300 mg, 400 mg, and 600 mg tablets.

How should I use this medication?

The usual recommended adult dose of cimetidine ranges from 200 mg twice a day to 600 mg 4 times a day (usually with meals and at bedtime), depending on the condition being treated. The maximum recommended dose of cimetidine is 2,400 mg.

Children's doses are based on the weight of the child, usually 20 mg to 40 mg per kilogram of body weight daily, divided into 4 doses.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

Cimetidine can be taken with or without food.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Cimetidine should not be taken by anyone who:

  • is allergic to cimetidine or to any of the ingredients of the medication
  • is allergic to other acid-reducing agents known as H2-receptor antagonists (e.g., famotidine, ranitidine, and nizatidine)

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent. The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • decreased sexual desire
  • decreased sexual ability (especially for people with Zollinger-Ellison syndrome who have been taking high doses of cimetidine for at least one year)
  • diarrhea
  • drowsiness
  • headache
  • loss of hair
  • nausea or vomiting
  • swelling of the breasts or breast soreness (women and men)

Although most of these side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.

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

  • abdominal pain
  • back, leg, or stomach pain
  • bleeding or crusting sores on the lips
  • blisters on palms of hands and soles of feet
  • changes in vision or blurred vision
  • dizziness
  • fainting
  • fast, pounding, or irregular heartbeat
  • general feeling of discomfort or illness
  • mood or mental changes (e.g., anxiety, agitation, confusion, hallucinations, depression, nervousness, or severe mental illness)
  • muscle cramps or aches
  • red or irritated eyes
  • signs of allergic reaction (e.g., hives, skin rash, or itching)
  • signs of bleeding (e.g., bloody nose, blood in urine, coughing blood, cuts that don't stop bleeding)
  • signs of infection (e.g., coughing or difficulty swallowing, sore throat, fever or chills, flu-like symptoms, swollen or painful glands)
  • signs of liver problems (e.g., nausea, vomiting, diarrhea, loss of appetite, weight loss, yellowing of the skin or whites of the eyes, dark urine, pale stools)
  • slow heartbeat
  • sores, ulcers, or white spots on the lips, in the mouth, or on the genitals
  • swelling of the hands or feet
  • tightness in the chest
  • troubled breathing
  • unusually slow or irregular breathing
  • wheezing

Stop taking the medication and seek immediate medical attention if any of the following occur:

  • signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)
  • signs of inflammation of blood vessels (e.g., fever, fatigue, weight loss, loss of appetite, headache, numbness or weakness, muscle or joint pain)
  • symptoms of a severe skin rash (e.g., blistering, peeling, a rash covering a large area of the body, a rash that spreads quickly, or a rash combined with fever or discomfort)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Kidney function: People with kidney disease are at risk for increased side effects. People with kidney disease or reduced kidney function should discuss with their doctor how this medication may affect their medical condition, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver function: People with liver disease or reduced liver function should discuss with their doctor how this medication may affect their medical condition, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Pregnancy: The safety of this medication for use during pregnancy has not been established. This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: This medication passes into breast milk. If you are a breast-feeding mother and are taking cimetidine, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

What other drugs could interact with this medication?

There may be an interaction between cimetidine and any of the following:

  • alcohol
  • amiodarone
  • azole antifungal medications (e.g., fluconazole, ketoconazole)
  • caffeine
  • calcium channel blockers (e.g., diltiazem, nifedipine, verapamil)
  • carbamazepine
  • carmustine
  • carvedilol
  • certain benzodiazepines (alprazolam, chlordiazepoxide, clonazepam, clorazepate, diazepam, flurazepam, midazolam, and triazolam)
  • cisapride
  • chloroquine
  • clopidogrel
  • clozipine
  • colchicines
  • dasatanib
  • delaveridine
  • dofetilide
  • epirubicin
  • fentanyl
  • glyburide (and other "sulfonylurea" diabetes medications)
  • lidocaine
  • mesalamine
  • metformin
  • methylphenidate
  • metoprolol
  • moclobamide
  • pentoxifylline
  • phenytoin
  • praziquantel
  • procainamide
  • propranolol
  • quinidine
  • quinine
  • salmeterol
  • SSRIs (e.g., citalopram, fluoxetine, sertraline)
  • St. John's wort
  • sucralfate
  • tamoxifen
  • theophyllines (e.g., aminophylline, oxtriphylline, theophylline)
  • thioridazine
  • tramadol
  • tricyclic antidepressants (e.g., amitriptyline, imipramine)
  • warfarin

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.