Zantac - How to use | Dosage | Side Effects

This article was medically reviewed by M.Pharm, Marko Tanaskovic on August 12, 2018. To read more about an author, click here.

Zantac is a medicine that contains an active substance called ranitidine. It belongs to a group of medicines called H2 antihistamines. It reduces gastric acid secretion, therefore is used in the treatment of gastric or duodenal ulcer, gastroesophageal reflux disease and Zollinger-Ellison syndrome.


Zantac should be avoided in patients allergic to the active substance ranitidine or other similar medicines (e.g. famotidine).

The possibility of stomach cancer should be excluded before you start using this medicine, because this medicine may mask the symptoms of stomach cancer and delay diagnosis of this condition.

In patients with kidney diseases, the dose should be reduced, because this drug is excreted through the kidneys.

Rarely, there have been reports of acute porphyria during treatment with this medicine, therefore this medicine should be used with extra precautions in patients who have had an acute porphyria.

Elderly patients and patients with diabetes are at greater risk of community-acquired pneumonia. If you are experiencing symptoms of pneumonia, such as:

  • cough,
  • fever,
  • chest pain

contact your doctor immediately.

In addition to taking this medicine, you need to make lifestyle changes (eat several smaller meals throughout the day, avoid oily and spicy foods, and quit smoking).

Use during pregnancy and breastfeeding

Zantac drug should not be used during pregnancy unless the benefit to the mother outweighs the risk to the child. Consult your doctor about the benefits and risks of using this drug during pregnancy.

Zantac passes into breast milk, therefore you should avoid breastfeeding while using this drug.

How to use

Considering that Zantac has most impact on nocturnal basal acid secretion, it is recommended to take this medicine in the evening, an hour before bedtime. It can be taken regardless of food because food does not affect this medication.

The usual dose is Zantac 150 mg once a day, at bedtime, or 150 mg twice a day (in the morning and in the evening). Patients with stomach or duodenal ulcers should take this drug for at least a month to feel improvement.

Swallow the tablet whole with a glass of water. Do not crush or chew the tablet.

Zantac dosage forms also include effervescent tablets, which should be dissolved in 100 ml of water and drunk all at once, preferably in the evening.

The dose should be reduced in elderly patients and in patients with kidney disorders.

In children avobe the age of 3, Zantac can be used only with medical advice. Dose is calculated based on body weight.

It is very important to change the diet and avoid fatty and spicy foods, as well as to quit smoking in order to achieve efficient treatment.

Use with other medicines (Interactions)

It should be avoided in combination with the following medicines:

  • Warfarin, a drug used in the treatment of thrombosis.
  • Benzodiazepines, drugs used to treat insomnia and anxiety, such as midazolam.
  • Glipizide, a drug used in the treatment of diabetes.

It should not be used in combination with alcoholic beverages.

Zantac side effects

Zantac may cause the following side effects:

  1. nausea,
  2. vomiting,
  3. abdominal pain,
  4. constipation,
  5. slow heart rate (bradycardia),
  6. rapid heart rate (tachycardia),
  7. headache,
  8. dizziness,
  9. blurred vision,
  10. muscle pain,
  11. joint pain,
  12. decrease in the white blood cell count (agranulocytosis),
  13. decreased libido,
  14. fatigue,
  15. allergy and others.

Tell your doctor if you are experiencing any side effects.

Information on this website are provided for educational purposes only and are not intended for medical advice, diagnosis or treatment.

If you have any concerns or questions about your health, you should always consult with a physician or other health-care professional.

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