Cimetidine

Cimetidine is both an over-the-counter and a prescription medication. The over-the-counter form is used to treat heartburn, indigestion and a sour stomach. The prescription form is used to treat acid reflux, conditions that cause your stomach to release too much acid, and stomach ulcers.

Cimetidine belongs to a group of drugs called Histamine H2 Receptor Antagonists. It works by decreasing the amount of acid produced in the stomach. 

This medication comes in tablet and oral liquid form. Cimetidine is taken by mouth, up to 4 times a day. It is best to take it up to 30 minutes before eating. 

Common side effects of cimetidine include headaches, dizziness, and diarrhea. Cimetidine can also cause drowsiness. Do not drive or operate heavy machinery until you know how cimetidine affects you.

Cimetidine is both an over-the-counter and a prescription medication. The over-the-counter form is used to treat heartburn, indigestion and a sour stomach. The prescription form is used to treat acid reflux and stomach ulcers. 

This medication may be prescribed for other uses. Ask your doctor or pharmacist for more information.

Cimetidine may be found in some form under the following brand names:

• Tagamet

Serious side effects have been reported with cimetidine. See the “Cimetidine Precautions” section.

Common side effects include:

• Headaches
• Dizziness
• Drowsiness
• Diarrhea
• Breast development in males

This is not a complete list of side effects. Ask your doctor or pharmacist for more information. Tell your doctor if you have any side effect that bothers you or that does not go away. Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Tell your doctor about all the medicines you take, including prescription and non-prescription medicines, vitamins, and herbal supplements. Especially tell your doctor if you take:

• Oral cancer medications like bosutinib (Bosulif), dasatinib (Sprycel), ibrutinib (Imbruvica), olaparib (Lynparza), and pazopanib (Votrient)
• Dofetilide (Tikosyn)
• Certain anti-viral medications like delavirdine (Rescriptor) and Simeprevir (Olysio)
• Risedronate (Actonel)
• Clopidogrel (Plavix)
• Warfarin (Coumadin)
• Medications that block the p-glycoprotein transporter such as amiodarone (Cordarone, Pacerone), azithromycin (Zithromax, Zmax), captopril (Capoten), carvedilol (Coreg), clarithromycin (Biaxin), conivaptan (Vaprisol), cyclosporine (Neoral, Sandimmune, Gengraf), diltiazem (Cardizem), dronedarone (Multaq), erythromycin (EES, Ery-Tab), felodipine (Plendil),  itraconazole (Sporanox, Onmel), ketoconazole (Nizoral), lopinavir and ritonavir (Kaletra), quinidine (Cardioquine, Quinact, Duraquin), ranolazine (Ranexa), and verapamil (Calan, Isoptin, Covera, Verelan)
• Medications that use the enzyme CYP3A4 such as budesonide (Entocort), astemizole (Hismanal), cisapride (Propulsid), cyclosporine (Neoral, Gengraf, Sandimmune), darifenacin (Enablex), dihydroergotamine (Migranal), fentanyl (Abstral, Fentora, Onsolis, Actiq), pimozide (Orap), quinidine (Cardioquin, Duraquin, Quinact), sirolimus (Rapamune), tacrolimus (Prograf), terfenadine (Seldane), fluticasone (Flovent HFA, Flonase), eletriptan (Relpax), lovastatin (Mevacor), quetiapine (Seroquel), sildenafil (Viagra, Revatio), and simvastatin (Zocor)
• Medications that use the enzyme CYP1A2 such as alosetron (Lotronex), caffeine, clozapine (Clozaril), flutamide (Eulexin), frovatriptan (Frova), melatonin, mexiletine (Mexitil),  mirtazapine (Remeron), olanzapine (Zyprexa), ramelteon (Rozerem), rasagiline (Azilect), ropinirole (Requip), tacrine (Cognex), theophylline, tizanidine (Zanaflex), triamterene (Dyrenium), zolmitriptan (Zomig)
• Medications that use the enzyme CYP2D6 such as desipramine, dextromethorphan, atomoxetine, and metoprolol

This is not a complete list of drug interactions. Ask your doctor or pharmacist for more information.

Serious side effects have been reported with cimetidine including the following:

• Confusion
• Vitamin B12 deficiency
• Agitation or excitement
• Liver damage
• Kidney damage

Cimetidine can cause drowsiness. Do not drive or operate heavy machinery until you know how cimetidine affects you.

Do not take cimetidine if you:

• are allergic to cimetidine or any of its ingredients
• are allergic to any other Histamine H2 Receptor Antagonist like Rantidine (Zantac), Famotidine (Pepcid), or Nizatidine (Axid)

Medications can interact with certain foods. In some cases, this may be harmful and your doctor may advise you to avoid certain foods. In the case of cimetidine, there are no specific foods that you must exclude from your diet when receiving this medication.

Before taking cimetidine, tell your doctor about all of your medical conditions. Especially tell your doctor if you:

Tell your doctor about all the medicines you take including prescription and non-prescription medicines, vitamins, and herbal supplements.

Tell your doctor if you are pregnant or plan to become pregnant.

The FDA categorizes medications based on safety for use during pregnancy. Five categories - A, B, C, D, and X, are used to classify the possible risks to an unborn baby when a medication is taken during pregnancy.

Cimetidine falls into category B. There are no well-done studies that have been done in humans with cimetidine. In animal studies, pregnant animals were given this medication, and the babies did not show any medical issues related to this medication.

Tell your doctor if you are breastfeeding or plan to breastfeed.

Cimetidine has been detected in human breast milk. Because of the possibility for adverse reactions in nursing infants from cimetidine, a choice should be made whether to stop nursing or to stop use of this medication. The importance of the drug to the mother should be considered.

Take cimetidine exactly as prescribed. If you are taking the over-the-counter (OTC) version, take cimetidine exactly as recommended on the packaging. 

This medication comes in tablet and oral liquid forms. Cimetidine is taken by mouth, up to 4 times a day. It is best to take it up to 30 minutes before eating. 

If you miss a dose, take the missed dose as soon as you remember. If it is almost time for the next dose, skip the missed dose and take your next dose at the regular time. Do not take two doses of cimetidine at the same time.

Take this medication exactly as prescribed by your doctor. If you are taking the over-the-counter (OTC) version, follow the directions on the packaging carefully.

If your doctor prescribes cimetidine to you, the dose your doctor recommends may be based on the following:

• the condition being treated
• other medical conditions you have
• other medications you are taking
• how you respond to this medication
• your weight
• your height
• your age
• your gender

If your doctor prescribes this medication to you, the usual dose can vary between 400 mg once daily to four times daily for the treatment of stomach ulcers, acid reflux, and conditions that cause your stomach to release too much acid. The maximum dose for prescription cimetidine is 600 mg four times a day. 

If you are taking the OTC version of cimetidine, the dose is usually 200 mg once or twice a day for the treatment of heartburn, indigestion, and a sour stomach. The maximum dose for OTC cimetidine is 200 mg twice a day.

If you take too much cimetidine, call your healthcare provider or local Poison Control Center, or seek emergency medical attention right away.

If cimetidine is administered by a healthcare provider in a medical setting, it is unlikely that an overdose will occur. However, if overdose is suspected, seek emergency medical attention.

• Store cimetidine at room temperature.
• Keep this and all medicines out of the reach of children.
• Keep away from light.