Ranitidine: Dosage and Precautions

Patients typically take ranitidine orally. If this route of administration isn't an option, there are vials available for intravenous or intramuscular injection.
Ranitidine: Dosage and Precautions

Last update: 22 January, 2021

Ranitidine is an antihistamine medication with specific and fast action. It reduces stomach acid secretion, both the amount secreted and baseline. In this manner, ranitidine lowers the volume and the amount of acid and pepsin secreted.

Its effects are rather long-lasting. This is why a single dose of 150 mg can effectively reduce gastric acid secretion for 12 hours. What else should you know about ranitidine? Read on and we’ll give you all the information.

A brief history of ranitidine

Glaxo pharmaceuticals company developed this medication based on cimetidine, the first antihistamine they developed. In this way, ranitidine was the result of a design process. Researchers wanted to refine the compound by replacing certain chemical groups.

With these results, they were able to synthesize ranitidine, which has a better tolerance profile. That’s to say, the adverse reactions to the medication are far less.

Furthermore, it offers prolonged action and a 4 to 10 times greater effect than cimetidine. It entered the market in 1981 and was the top-selling prescription drug in 1988. Since then, it has been replaced by even more effective pharmaceuticals for these indications.

Popping a pill.
Ranitidine was the result of a design process that Glaxo pharmaceuticals company developed.

What is histamine?

Histamine is a substance that belongs to the imidazole chemical family, which is involved in localized immune responses. It also regulates normal functions in the stomach and acts as a neurotransmitter in the central nervous system.

Neurotransmitters are substances that the body makes naturally, and whose main function is to regulate the synapses between neurons. In other words, they regulate the chemical reactions between neurons when they transmit signals.

In this manner, the electrical connections become more complete and give rise to many more possibilities. If neurotransmitters didn’t exist, and neurons simply acted as “wires,” it wouldn’t be possible for the nervous system to carry out many of its functions.

On the other hand, there’s new evidence that shows that histamine also plays a role in chemotaxis of white blood cells, such as eosinophils.

Scientists have known about histamine since the 1950s. However, they’re just recently discovering its functions in the body.


The indications for this medication are related to its ability to antagonize histamine H2 receptors. Among these we can mention:

  • Duodenal ulcer
  • Benign gastric ulcer
  • Gastric reflux and treatment of associated symptoms
  • Zollinger-Ellison syndrome
  • Treatment of esophageal and gastric hemorrhage with hypersecretion, and prevention of recurring hemorrhage in patients with bleeding ulcers

In addition to the indications mentioned above, doctors prescribe ranitidine for the prevention of gastrointestinal hemorrhage caused by stress ulcers in the gravely ill.

It’s also administered preoperatively to patients with a risk of acid aspiration syndrome, known as Mendelson syndrome. Additionally, doctors often administer it to mothers during childbirth.

Posology (dosage)

Ranitidine is an oral medication. If this method can’t be used, there are vials available for intravenous or intramuscular injection. However, doctors typically resort to this route of administration in a hospital setting only.

Depending on the indication for which ranitidine has been prescribed, the concentration will vary.

  • Duodenal ulcer in adults: The dose is 150 mg every 12 hours, or 300 mg at night for 4-6 weeks. For children, it’s 2mg per kilogram of the child’s weight every 12 hours.
  • Gastric ulcer in adults: 150 mg every 12 hours, or 300 mg at night for 6-8 weeks. For associated symptoms, the dose is 150 mg every 12 hours for 2 weeks, and the treatment can be extended if the initial response is poor.
  • Zollinger-Ellison syndrome: The starting dose will be 150mg every 8 hours. The doctor can increase the dose incrementally depending on the patient’s response. However, the maximum dose for this medication is 6 grams per day.

The drug data sheet must be consulted for other indications. It includes all the information related to ranitidine.

Precautions when using ranitidine

A consultation.
Before using ranitidine, it’s important to be aware of possible side effects and contraindications.

When using ranitidine, patients must take precautions in a variety of situations that require dose adjustment to avoid serious complications. That is the case for patients who have some of the following conditions:

  • Renal insufficiency: the dose will need adjustment.
  • Interference in the diagnosis of carcinoma – ranitidine can delay the symptoms of this type of cancer, which can delay diagnosis.
  • Interference in other diagnostic tests.
  • Pregnancy and breastfeeding.


In summary, ranitidine is a medication with widespread use. It’s an antihistamine medication available by prescription from a doctor. Patients should follow the usage recommendations provided by their doctor. This medication isn’t free from adverse effects and could cause a number of complications.

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