Medication Information Leaflet

​What is this medication for?

Cimetidine works by reducing the amount of acid produced in the stomach. It is used to treat various conditions of the gastrointestinal (stomach and intestines) tract including:
  • Gastro-oesophageal reflux disease (a condition where the acid from the stomach goes back up the food tube and throat, causing pain and a burning sensation known as heartburn)
  • Treating and preventing ulcers of the gastrointestinal tract

How should I take/use this medication?

  • Do not stop taking your medication without checking with your healthcare professional.
  • You may take this medication with or without food.

What should I do if I forget to take/use this medication?

If you forget to take a dose, take it as soon as you remember. Then take your next dose at the usual time. Do not take two doses to make up for the missed dose. 

What precautions should I take?

Inform your healthcare professional if:
  • You are allergic to this medication or any of the other ingredients of this medication
  • You are pregnant, planning to become pregnant, or breastfeeding 
  • You have a history of liver and/or kidney disease
  • You have been diagnosed with a rare inherited disease known as porphyria. This condition affects the production of red blood cells
  • You are taking any other medications, including supplements, traditional medications and herbal remedies.

What are some common side-effects of this medication?

  • Side effects of cimetidine include stomach pain, constipation, nausea, headaches and rarely blurred vision.
    • Please consult your healthcare professional if the symptoms do not go away or when any unexplained or unusual symptoms occur

What are some rare but serious side-effects that I need to seek medical advice immediately?

The symptoms of a drug allergy include one or more of the following:
  • Swollen face/eyes/lips/tongue
  • Difficulty in breathing
  • Itchy skin rashes over your whole body
Signs that your condition may require further medical attention include:
  • Shortness of breath, hoarseness, wheezing, teeth erosion and ear infection
  • Alarm features including pain on swallowing, swallowing difficulty, blood in the stools or vomit, chest pain, unintended weight loss and jaundice (yellowing of the skin and whites of the eyes)
  • Heartburn symptoms occurring for more than 3 times a week with serious impact on quality of life
  • Heartburn symptoms continuing for more than 2 weeks despite self-treatment
  • Heartburn symptoms continuing for over 3 months regardless of self-treatment
  • You are over 40 years old and experiencing heartburn symptoms for the first time
If you experience any of the symptoms mentioned above, you should stop your medication and see your healthcare professional immediately.

What food or medication should I avoid when I take this medication?

This medication may decrease the absorption of several vitamins and minerals such as:
  • Vitamin B12
  • Magnesium
  • Iron
Speak with your healthcare professional to determine if you need to supplement these vitamins and minerals.

This medication interacts with many types of long-term medications. This may result in more side effects from your long-term medication, or may make other medications less effective. Medications affected by cimetidine include but are not limited to:

  • High blood pressure medication e.g. Nifedipine
  • Medications for your heart e.g. Metoprolol, Amiodarone, Flecainide
  • Medication to treat fungal infections e.g. Ketoconazole, itraconazole
  • Medication to thin the blood e.g. Warfarin
  • Medication to stabilise mood e.g. Amitriptyline, Diazepam
  • Medication to treat seizures e.g. Carbamazepine, Phenytoin
  • Medications to suppress the immune system e.g. Tacrolimus, Cyclosporine, Hydroxychloroquine
  • Medications for migraine e.g. Cafergot
Inform your healthcare professional if you are taking or intend to take any other medications, supplements, traditional medications or herbal remedies.

How should I store this medication?

Store in a cool and dry place, away from direct sunlight. Keep this medication away from children.

How should I throw away this medication safely?

Pack this medication into a black trash bag and seal it tightly before throwing into the rubbish chute or bin.

If you take more than the recommended dose, please seek medical advice immediately. The information provided on this page does not replace information from your healthcare professional. Please consult your healthcare professional for more information.

This article is jointly developed by members of the National Medication Information workgroup. The workgroup consists of cluster partners (National Healthcare Group, National University Health System and SingHealth), community pharmacies (Guardian, Unity and Watsons) and Pharmaceutical Society of Singapore.

Last reviewed on December 2019
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