Prescription or OTCLower-cost generic available



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Relieves heartburn and acid tummy.

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Prescription or OTCLower-cost generic available

Our bottom line

Tagamet (Cimetidine) works well for heartburn but may not last as long or start working as quickly as other antacids.


  • Most people can take Cimetidine without any noticeable day-to-day side effects.
  • Cimetidine lasts longer than many other antacids like Maalox and Tums, and you only need to take it once or twice a day.
  • You can take it in combination with a quick-acting antacid (like Maalox or Tums) if you need relief right away.
  • Available as both a generic and over-the-counter option, so it's pretty affordable.
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  • Other antacids like Maalox, Tums, or Rolaids often start to work more quickly than Cimetidine.
  • Medication like omeprazole (proton pump inhibitors) works better at healing and preventing stomach ulcers than medication like Cimetidine (H2 blockers).
  • Has more drug interactions than zantac and pepcid.
  • Although rare, Cimetidine can cause large breasts or impotence for men who need to use high doses for 6 months or more. It's reversible though and should go away when you stop or if you change medication.

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What to expect when you take Tagamet (Cimetidine)

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Tips from our pharmacists
  • Works best if you take it with a full glass of water.
  • Starts working in one hour.
  • If heartburn doesn't improve or lasts more than 2 weeks, talk to your doctor.
  • People with kidney disease may need to take a lower dose.
  • Tell your doctor all of the medications that you use before taking Cimetidine to avoid drug interactions.
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Side effects for Tagamet (Cimetidine)

From clinical trials of Tagamet / GI ulcer 

  • Abnormally large breasts in malesAbnormally large breasts in males4% for Cimetidine vs.0% for placebo
  • DiarrheaDiarrhea1% for Cimetidine vs.0% for placebo

Manufacturers don’t say how common these side effects are

  • Decreased white blood cell counts
  • Increase in plasma creatinine
  • Increase in serum transaminase
  • Mild rash
  • Reversible confusional states
  • Reversible impotence

Risks and Warnings for Tagamet (Cimetidine)

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  • Heartburn and feelings of upset stomach can be warning signs of a more serious stomach problem or cancer. If you need to take Tagamet (Cimetidine) for 2 weeks or more go see a doctor. It's safest to get checked out to make sure you do not have a serious stomach condition.

Means that some groups have a high risk of experiencing this side effect

Tips from pharmacists and people taking Tagamet (Cimetidine)

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The FDA category for this medication is B. It is advised that you: Probably safe
Kidneys and liver
  • Tips from our pharmacists
  • People with kidney disease may need to take a lower dose.
  • Risks from our pharmacists
  • Tagamet (Cimetidine) can cause states of intense confusion. This is usually reversible when you stop taking Tagamet (Cimetidine). If you have kidney problems, you may need a different dose to prevent this increased risk for side effects. However, stopping Tagamet (Cimetidine) completely may be necessary.