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Generic Name

cimetidine (si MET i deen)


Trade Name



What is cimetidine?

Cimetidine was the very first drug specifically designed to block the acid producing cell in the stomach. The location of cimetidine’s action within the cell is the histamine 2 site so this and other drugs like it are called histamine 2 receptor antagonists or H2RA for short. The drug proved to be remarkably effective in healing and preventing the return of ulcers. It has been found to be fairly safe for long-term use as well. Since the generic form is the least expensive way of controlling stomach acid, many physicians recommend this preparation for various stomach acid conditions when it proves to be effective.


What is it used for?

Cimetidine can be effective in the following conditions:

  • Healing and prevention of peptic ulcers in the stomach or duodenum
  • Reflux of acid into the esophagus (Gastroesophageal Reflux Disease)
  • Hyperacidity
  • Zollinger-Ellison Syndrome – a rare condition where very large amounts of acid pour from the stomach. However, there are now much more effective medications for this condition
  • There are also many other “unlabeled” (not FDA approved) uses of cimetidine


How do I take it?

Follow your physician’s instructions carefully. Cimetidine may be taken with or between meals. It is usually necessary to take the drug 3 to 4 times a day since it is most effective in suppressing stomach acid for 4 to 5 hours. Do not take it at the same time you use antacids. Store in a tightly closed container away from light. Keep all medications away from children. Never share your medications with anyone else.


What do I do for a missed dose?

If you forget, take it as soon as you remember. However, if it is time for your next dose, simply take that one and do not double up.


Are there interactions with food or beverages?

There is no interaction between cimetidine and any food or beverage including alcohol. However, both caffeine and alcohol stimulate the production of stomach acid and may make symptoms worse.


Are there interactions with other drugs?

An interaction generally means that one drug may increase or decrease the effect of another drug. Also, the more medications a person takes, the more likely there will be a drug interaction.

Cimetidine is metabolized at a certain place in the liver where many other drugs are also broken down. So there are potential interactions with many other drugs. However, in clinical practice, physicians have seen remarkably few problems. Still, if you take any of the following, you should check with your physician.

Interactions with this drug may occur with the following:

  • amoxicillin (Augmentin)
  • anti-depressants (Elavil)
  • anti-diabetic drugs (Micronase, Glucotrol)
  • aspirin
  • benzodiazepine tranquilizers (Valium, Xanax, Librium)
  • beta-blockers (Inderal, Lopressor)
  • blood thinners (Coumadin)
  • calcium-blockers (Cardizem, Calan, Procardia)
  • carbamazepine (Tegretol)
  • chemotherapy drugs – some
  • chlorpromazine (Thorazine)
  • cisapride (Propulsid)
  • clozapine (Clozaril)
  • cyclosporine (Sandimmune, Neoral)
  • digoxin (Lanoxin)
  • fluconazole (Diflucan)
  • ketoconazole (Nizoral)
  • medication for irregular heartbeat (Cordarone, Tonocard, Quindex, Procanbid)
  • metoclopramide (Reglan)
  • metronidazole (Flagyl)
  • narcotic (Demerol, morphine)
  • nicotine ( Nicoderm, Nicorette)
  • paroxetine (Paxil)
  • pentoxifylline (Trental)
  • phenytoin (Dilantin)
  • quinidine (Quinidex, Quinaglute)
  • sucralfate (Carafate)
  • theophylline (Theo-Dur)


Is there a problem if I have another disorder or disease?

At times, a drug may have a different or enhanced effect when other diseases are present. At other times, the drug may worsen or effect another disease.

With this drug the following disorders may be a problem:

  • chronic kidney disease
  • chronic liver disease
  • low sperm count


What about allergies?

People who have known allergies or asthma may be at an increased risk for a reaction from any new medication. The physician should always know a patient’s allergy history. Signs of an allergic reaction are skin rash, itching and hives. Of course, a person should not take cimetidine if there has been a previous reaction to this or other H2RA medications.


What if I’m pregnant, considering pregnancy or breast-feeding?

Most females now know that, if possible, no drug, including alcohol, should be taken during pregnancy or lactation. The potential danger, of course, is an injury to the baby. However, some drugs are much safer than others in this regard. So, the FDA has a grading system for each drug which reflects what is known medically. It ranks drugs from A, where medical studies show no evidence for danger to the fetus or mother, to B, C, D and X, where the medical evidence indicates that the risk to the fetus outweighs any benefit to the mother. Cimetidine is ranked B. Always consult your physician before taking any drug during or when planning pregnancy.


What are the effects on sexual function?

Cimetidine may cause breast swelling in males, loss of libido and impotence. These conditions are not permanent and are reversed when the drug is discontinued.


Are there other precautions?

Confusion may occur in elderly patients. Do not drive or engage in hazardous activities until the effect on alertness is known.


How long is it safe to take cimetidine?

Cimetidine can be taken indefinitely. However, if you have had an ulcer, remember that 95% of stomach or duodenal ulcers are caused by Helicobacter pylori bacteria infection (which can be cured by antibiotics) or by aspirin or arthritis medication. Long-term use of cimetidine should not be necessary under these conditions. Do not take over-the-counter doses for more than two weeks without physician approval.


How about side effects?

Adverse reactions can occur with any drug, even over-the-counter medications. Some of these are mild such as a stomach upset, which may be avoided by taking the medication with food. Minor reactions may go away on their own but, if they persist, contact the physician. For major reactions, the patient should contact the physician immediately.

For cimetidine, the following are the observed side effects:


  • breast swelling or tenderness in men
  • headache
  • rash
  • diarrhea
  • achy joints
  • dizziness
  • muscular pain
  • hair loss
  • reduced sexual potency
  • reduced sperm count


  • hallucinations or mental confusion (more common in the elderly)
  • unusual fatigue
  • fever
  • sore throat
  • shortness of breath
  • abnormal skin bruising


A physician’s comment..

Cimetidine deserves a plaque in the museum of drug history. It was almost the first drug developed by a pharmaceutical company to do a specific job – i.e. to block a specific chemical site in a cell. It revolutionized the treatment of peptic ulcer disease and opened up large areas of research for the development of other more effective drugs which, indeed, has occurred. If this drug is effective in treating the acid condition, there is nothing less expensive than the generic form.