Cimetidine: Uses, Side effects, Dosage

Cimetidine is a highly effective drug for reducing the amount of acid produced in the stomach. This medicine should be taken 30 minutes before the meal to relieve the symptoms of heartburn. It is necessary to monitor kidney function and central nervous system effects.

It is the antagonist of the histamine type 2 receptor. It is used in gastrointestinal disorders such as gastric ulcers and gastroesophageal reflux disease (GERD).
It shows many clinically significant drug interactions due to the inhibition of CYP450 enzymes.

Cimetidine Uses

It is used in the treatment and prevention of the following symptoms and diseases.

  • Gastric Ulcer
  • Zollinger-Ellison Syndrome
  • Duodenal Ulcer
  • Gastroesophagal Reflux Disease
  • Heart burn
  • Stress ulcers,
  • Hives, and
  • Itching.
  • Pneumonia during anesthesia.

Mechanism of action

Cimetidine binds to an H2 receptor, which is found in the parietal cell’s basolateral membrane and blocks the effect of histamine. This competitive inhibition results in a reduction in gastric acid secretion and a reduction in gastric volume and acidity.

Side Effects

Common Side Effects 

  • Headache
  • Drowsiness
  • Dizziness
  • Diarrhea

Serious Side Effects of Cimetidine

serious side effects are

  • Depression
  • Nervousness
  • Anxiety
  • Hallucinations
  • Confusion
  • Excitement
  • Anxiety
  • Decreased sexual ability
  • Breast enlargement
  • Unusual bruising or bleeding
  • Muscle pain or weakness
  • Severe stomach pain
  • Fast or slow heartbeat

Pregnancy & Breastfeeding

Cimetidine is unlikely to harm the unborn child. Tell your doctor if you are pregnant or planning to become pregnant before taking this medicine.

The drug can pass into breast milk and harm a baby. Do not take Cimetidine if you are breast-feeding.


  • Duodenal ulcers are treated with 800 to 1600 mg at bedtime or 300 mg 4 times daily at mealtime and bedtime, or 400 mg twice daily for 4-6 weeks. The maintenance treatment is 400 mg before bedtime.
  • Active gastric ulcers are treated with 800 mg at bedtime or 300 mg 4 times daily with meals and at sleep times for up to 8 weeks.
  • Hypersecreted pathological conditions are treated daily with 300 mg up to 2400 mg daily.
  • The treatment for GERD is 800 mg twice daily or four times 400 mg for 12 weeks.
  • Heartburn, indigestion and / or stomach acid can be treated with 200 mg once or twice daily and can be given up to 30 minutes before eating any foods or drinks that can cause heartburn.
  • In hospitalized patients who can not take oral medications, 300 mg of cimetidine may be injected intravenously or intramuscularly every 6 to 8 hours. A continuous intravenous infusion of 37.5 to 50 mg / hour may also be used.
  • Other doses of IV or IM cimetidine may be used for erosive esophagitis, upper bleeding or other disorders.
  • If overdose is suspected, call your healthcare provider or local Poison Control Center, or seek emergency medical attention right away.


Do not take cimetidine if you take the following drugs:

  • Dofetilide
  • Pimozide
  • Cisapride

This medicine may also interact with the following medications:

  • Carbamazepine
  • Carmustine
  • Caffeine
  • contraceptive or birth control pills
  • Itraconazole
  • Delavirdine
  • Ketoconazole
  • Theophylline
  • Medicines for heart rhythm problems
  • Phenytoin
  • warfarin

Frequently asked questions

1. Is it safe to drink alcohol with cimetidine?

In patients receiving cimetidine, alcohol consumption is not recommended. All symptoms of side effects such as dizziness, shortness of breath should inform the doctor. Performing educational activities that require mental alertness, such as driving or operating machines, should be avoided.

2. Is It Safe to Take Cimetidine During Pregnancy?

This medication is only recommended in pregnant women if the benefits outweigh the risks.

3. Is cimetidine Safe During Breastfeeding?

It is known that this substance is excreted in breast milk. It is not recommended for lactating women.

4Is it safe to drive or operate heavy machinery when using this product?

Cimetidine can cause drowsiness and dizziness so it’s not recommended for use in case of driving or operating machine. Always consult your doctor before using this medicine.

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