H2 Receptor Antagonists

H2 receptor antagonists are medications that are prescribed to treat excess acid in the stomach.

  1. Treat conditions related to acid levels in the stomach.
  2. These include gastric ulcers and persistent heartburn.
  3. Sometimes referred to as H2 receptor blockers.

If you have any concerns about conditions relating to stomach acid levels, you can speak with one of our GMC-registered clinicians via our online video consultation service, from 9.30am to 4.30pm, five days a week.

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Product information

What are H2 receptor antagonists?

H2 receptor antagonists are used to treat various conditions where the presence or level of stomach acid causes various issues, such as gastric ulcers and chronic heartburn. In most cases, they do not cause side effects. 

What are gastric ulcers?

If you are vomiting blood, have dark, tarry like stools or experience a sharp pain that develops suddenly and gets progressively worse, you should seek immediate medical assistance.  

Gastric ulcers, sometimes known as stomach or peptic ulcers, are sores that present in the lining of the stomach and in the duodenum (the first segment of the small intestine). It’s thought that the condition is common in the UK, although the exact figures are unclear. Gastric ulcers can develop at any age, but are most common in people over the age of 60. 

What symptoms can gastric ulcers cause?

There are a number of symptoms associated with the condition, but the most common is a gnawing and burning sensation in the stomach. In some cases, there is no pain and the condition is only apparent when bleeding occurs. Pain can sometimes spread from the stomach to other areas of the body, most likely to the neck or the back. Symptoms tend to worsen at night when you are lying down or after a meal. Indigestion and heartburn often occur, and nausea, vomiting and weight loss are also possible. If you are vomiting blood, have dark, tarry like stools or experience a sharp pain that develops suddenly and gets progressively worse, you should seek immediate medical assistance.  

What causes gastric ulcers? 

Gastric ulcers are usually caused by an infection of the H-pylori bacteria (helicobacter pylori). These infections are common and do not always cause ulcers, and in many cases are symptomless. It’s only when the infection irritates the stomach lining that gastric ulcers can develop. 

Another common cause of gastric ulcers is the use of non-steroidal anti-inflammatory drugs (NSAIDs), the long-term use of which can result in a similar irritation to the lining of the stomach as infections. Many NSAIDs, including ibuprofen and aspirin, are available to buy over the counter, and most people will be able to use them without issue. Certain lifestyle and dietary choices have also been linked to the development of gastric ulcers, such as spicy foods, alcohol consumption and high levels of stress. However, evidence of this is not conclusive.

How are gastric ulcers treated?

Treatment for gastric ulcers depends on what the cause is in the first place. Typically, where the H-pylori bacteria is present, a simple course of antibiotics will help clear up the infection. You may need to take a proton pump inhibitor (PPI) or H2 receptor antagonist alongside it to manage symptoms in the meantime. 

In cases where the use of NSAIDs have resulted in symptoms, proton pump inhibitors or H2 receptor antagonists are used. With these treatments, gastric ulcers should clear up within a month or two and leave no lasting effects. Other medications to manage symptoms include antacids and alginates. Antacids, as the name suggests, reduce the amount of acid in the stomach, and help to ease the pain caused by the ulcer. They only provide short-term relief, however, and painful symptoms return without the use of the above treatments. Antacids often contain alginates, a substance that gives the lining of the stomach a protective layer.

What is chronic heartburn? 

Chronic heartburn is a burning sensation caused by the movements of stomach acid upwards towards the area of the throat. Symptoms may also include an acidic taste in the mouth, coughing, hiccups, bad breath, a deepening of the voice, nausea and bloating. There are many causes of heartburn, but it is not always clear why it occurs. The most likely causes include smoking, spicy food, obesity, carbonated drinks, alcohol, coffee, fatty foods, some medications, stress, anxiety, pregnancy, obesity, a hiatus hernia or a combination of some of these triggers. 

In many cases, these symptoms pass in a matter of hours, and can be avoided by making simple lifestyle choices. Measures such as eating smaller meals, losing weight, managing stress levels and avoiding some of the triggers outlined above can also help. 

When chronic heartburn does occur, raising the top half of the body slightly when in bed can provide relief. In chronic cases, in which symptoms are always present, treatment with medications, such as H2 receptor antagonists, may be required. 

If you would like to make an appointment to speak to a GPhC-registered clinician about H2 receptor antagonists or any related conditions, our online video consultation service is available from 9.30am-4.30pm, five days a week. Our clinicians can also issue fit notes and referral to specialists for treatment, where required. 

Page last reviewed:  15/07/2020
Side effects and warnings

What side effects can H2 receptor antagonists cause?

All medications can cause side effects, so it’s important to understand what these are before starting treatment. Your prescribing doctor can discuss any potential side effects of your medication with you, and the patient information leaflet that comes with your medication will list all the possible side effects. 

Because there are many different types of H2 receptor antagonists, side effects may differ from one specific type to the next. The following information relates to cimetidine. 

If you take cimetidine and experience any of the following side effects, seek immediate medical assistance as they may indicate an allergic reaction: rashes, itching, hives on the skin, swelling of the face and other parts of the body, shortness of breath, wheezing and trouble breathing.

In rare cases, the production of breast milk in males and females has been reported.

The most common side effects of cimetidine include diarrhoea, headaches, dizziness, rashes, tiredness, muscle pain and joint pain. These symptoms tend to be very mild and subside quickly. 

Very rarely, the following side effects can occur: hair loss, mouth ulcers, infections of the throat, fever, changes in the amount of urine passed and its colour, nausea, vomiting, confusion, confusion, anaemia, looking pale, frequent infections, bruising more easily, nose bleeds, liver inflammation, nausea, vomiting, loss of appetite, feeling unwell, itching, yellowing of the skin and eyes, dark coloured urine, slowing of the heartbeat, irregular heartbeat, fainting, impotence, depression, hallucinations and inflammation of the pancreas.

Can H2 receptor antagonists cause interactions with other medicines?

All medications have the potential to interact with other treatments, including supplements. It’s therefore essential that your prescribing doctor is aware of any medication you are currently or have recently taken in order to ensure that this treatment is safe for you. In the case of cimetidine, another treatment may need to be considered if you are taking any of the following: anticoagulants, anticonvulsants, bronchodilators, immunosuppressants, medicines that cause a fall in blood cell count, antifungals, heart medicines, antidiabetics, anti-cancer drugs, strong painkillers, tricyclic antidepressants, antiretroviral drugs and tacrolimus. 

Warnings and precautions when taking H2 receptor antagonists 

You should inform your prescribing clinician if you have any health conditions that H2 receptors are not used to treat before starting a course of treatment. In the case of cimetidine, this is particularly important if you have kidney problems, gastric cancer, liver problems, a history of peptic ulcers, if you are middle aged or older or have recently diagnosed indigestion and stomach cancer. 

Are H2 receptor antagonists safe to take if you are pregnant?

It’s important that you inform your doctor if you are pregnant or planning on becoming pregnant before starting treatment.  You should avoid using H2 receptor antagonists while you are breastfeeding. 

What types of H2 receptor antagonists are available?

There are different H2 receptor antagonists available, but all essentially work in the same way. The most common include ranitidine and cimetidine.

Page last reviewed:  15/07/2020
Questions and Answers

Is it safe to drive whilst using H2 receptor antagonists?

H2 receptor antagonists should not affect your ability to operate any form of heavy machinery.

Can H2 receptor antagonists cause any allergic reactions?  

If you have any allergies, you should inform your prescribing doctor before starting treatment. Many H2 receptor antagonist tablets contain lactose, which some people may have an intolerance of.

Can I buy H2 receptor antagonists over the counter? 

Some H2 receptor antagonists are available to buy over the counter, such as ranitidine, while others require a prescription.

Can I buy H2 receptor antagonists online?

You can discuss H2 receptor antagonists or any related conditions with a GMC-registered clinician using our online video consultation service. Our clinicians are available for appointments between 9.30am-4.30pm, Monday to Friday. They can also provide fit notes and referral to specialists for treatment, where appropriate. 


Page last reviewed:  15/07/2020

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