Nursing Student
New Grad
Join to watch the full lesson now.

10.04 Histamine 2 Receptor Blockers

Show More


  1. Histamine 2 Receptor Blockers
    1. Mechanism of action
      1. Blocks histamine from binding to histamine 2 receptors decreasing acid in the stomach
      2. Patho background
        1. Histamine 2 blockers are in the stomach
        2. Histamine binds to these blockers and stimulates acid prodcution
    2. Indications
      1. Stomach ulcers
      2. Peptic ulcer disease
      3. Intestinal ulcer
      4. Prevention of ulcers and acid reflux in hospitalized patients

Nursing Points


  1. Examples of Histamine 2 Receptor Blockers
    1. Cimetidine
      1. Able to cross the blood brain barrier
      2. Increased side effects
    2. Ranitidine
    3. Famotidine
    4. Nizatidine


  1. Assess for side effects
    1. Diarrhea
    2. Constipation
    3. Headache
    4. Fatigue
    5. Nausea
    6. Dry mouth
    7. Decreased RBC, WBC, Platelets
    8. Confusion – Cimetidine only
    9. Gynecomastia

Therapeutic Management

  1. Monitor RBC’s WBC’s and platelets closely

Nursing Concepts

  1. Pharmacology
    1. Histamine 2 Receptor Blockers are often prescribed to hospitalized patients to prevent acid reflux and the formation of ulcers.

Patient Education

  1. Hospitalized patients should be educated on why this medication is being administered.
Study Tools

Video Transcript

Histamine receptors blocker. So, in this video, we gonna talk about the histamine 2 receptor blocker. We already talked about the histamine 1, it’s time for histamine 2. So, where are these histamine 2 are located? Let’s talk about that first, then, we’ll be able to understand the mechanism of action of this class pretty easily. So, as we know, histamine 1 is inflammatory mediator receptors. So, it produce the inflammation and signs and symptoms. While these histamine 2 receptors are located in the stomach. And what the function is, when histamine comes and binds to this receptor, it produces this acid in our stomach.

So, as we know, this is the mechanism like when a histamine comes and binds to the histamine 2 receptors in stomach, it increases the secretions of acid in the stomach. That’s pretty much the work of the histamine when it binds to the histamine 2 receptor. Now, when we give this medication, histamine 2 receptor blocker, it blocks the effect of histamine on histamine 2 receptors, so it doesn’t let histamine produce, I mean it doesn’t let histamine to bind to histamine 2 receptor and it won’t be able to produce anymore acid in the stomach. So, that’s the mechanism of action of this histamine 2 receptor blocker medication that it decreases the, so basically, it decreases the secretion of acid in the stomach and intestine. ‘Cause there’s also some receptors in intestine and it prevents producing the acid in intestine either, intestine also.

So, what are the uses for this histamine 2 receptor? As we know, it prevents the production of acid so it can be used for stomach ulcers, peptic ulcer disease, could be used in intestinal ulcer, and also, it’s widely used as a prophylactic to prevent ulcer or acid reflux in hospital. Like a, when you have a patient in ICU, their body is under so much stress, they’re getting so many medications, they have a tube down to their throat, all the beeping, all the stress of ICU naturally produces more acid into their stomach. And when it produces more acid in their stomach and they’re lying in bed most of the, all the time, there’s a high chance they will have acid reflux and they can aspirate really badly. So, in order to prevent that acid reflux and aspiration of acids into their lungs, they usually put them on this prophylactic histamine 2 receptor blockers in ICU. So, that’s the one of the main use and widely used for that purpose as well.

What are the side effects? So, this medication causes many GI problems as well because it works on stomach and intestine. So, it definitely cause side effects on intestine. It can cause either diarrhea or constipation, either way, it can go. It can cause a bad headache, fatigue, nausea, it can cause a dry mouth, confusion. So, this particular side effects is caused by only one drug, Cimetidine. So, one drug, this is a drug in this class. And the reason this medication causes the confusion, it’s able to cross blood brain barrier. The rest of medication in this class will not be able to cross this blood brain barrier except the Cimetidine. So, if the patient is on Cimetidine, it can cause the confusion. The easier way to remember is like the first letter in this one is ‘C’ and it causes the CNS side effects. So, Cimetidine causes CNS side effects which is confusion. And it also can, these drugs also can decrease all blood cells types like the red blood cells, white blood cells and platelets. That’s why sometimes they need frequent lab drawn in able to make sure they don’t get any of the blood cells significantly lower that can cause more problems. And it can cause gynecomastia as well.

What are the examples of this medications? Ranitidine, Cimetidine, Famotidine and Nizatidine. It’s really easy to recognize these drugs as -tidine. TIDINE. TIDINE. And TIDINE. So, any drugs that ends with -tidine is a histamine 2 receptor blockers.

That’s really a short class. If you have any questions, any concerns about this video, just let us know.