Difference Between H1 and H2 Blockers

Thekey difference betweenH1 and H2 blockersis that H₁blockers refer to compounds that inhibit the activity of the H₁histamine receptorsthat occur throughout the vascularendothelial cellsin the heart and central nervous system, while H₂blockers refer to compounds that inhibit the activity of the H₂histamine receptors that mainly occur in the parietal cells of the gastric mucosa.

抗组胺药物使用医生治疗hay fever and allergies. Generally, people take antihistamines without prescriptions as they have few side effects. They relieve symptoms such as nasal congestion, sneezing, or hives caused by pollen, dust mites, or animal allergy. But they are usually for short-term treatment. There are several types of antihistamines. H1 and H2 blockers are two main types of antihistamines used to treatallergic reactions.

CONTENTS

1.Overview and Key Difference
2.What are H1 Blockers
3.What are H2 Blockers
4.Similarities – H1 and H2 Blockers
5.H1 vs H2 Blockers in Tabular Form
6.Summary – H1 vs H2 Blockers

What are H1 Blockers?

H₁blockers refer to compounds that inhibit the activity of the H₁histamine receptors. They occur throughout the vascular endothelial cells in the heart and central nervous system. They are also calledH1 antagonistsorH1 antihistamines. They help to relieve the symptoms of allergic reactions. H₁histamine receptors exhibit constitutive activity. Therefore, H₁blockers can be either neutral receptor antagonists or inverse agonists. Neutral receptor antagonists work by binding to the H1 receptor and blocking the activation of the receptor by histamine. On the other hand, inverse agonists work by binding to the H1 receptor and blocking the binding of histamine, and reducing the constitutive activity of the H1 receptor.

In the clinical setup, H1 blockers are used to treat allergic reactions and mast cell disorders. Sedation is a commonly found side effect of H1 blockers. Therefore, they are (diphenhydramine and doxylamine) normally used to treat insomnia. Moreover, H1 blockers can also be used to reduce inflammatory reactions. Some of the examples for H1 blockers are acrivastine, buclizine, cetirizine, desloratadine, hydroxyzine, levocetirizine, maprotiline, promethazine, phenyltoloxamine, orphenadrine, tripelennamine, etc.

What are H2 Blockers?

H2 blockers refer to compounds that inhibit the activity of H2 histamine receptors. They mainly occur in the parietal cells of the gastric mucosa. They are also called H2 antihistamine or H1 antagonists (H2RAs). They normally exist as inverse agonists and neutral antagonists. These H2 antihistamines act upon H2 histamine receptors, mainly in the parietal cells of the gastric mucosa. Parietal cells of the gastric mucosa are a part of the endogenous signalling pathway for gastric acid secretion. Usually, histamine acts upon H2 receptors to induce acid secretion. Thus, H2 blockers inhibit H2 signalling and reduce the secretion of gastric acid.

H2 blockers are the first-line treatment for gastrointestinal conditions, including peptic ulcers and gastroesophageal reflux disease. Further, they are also used for the treatment of dyspepsia. The common examples of H2 blockers are cimetidine, ranitidine, famotidine, nizatidine, roxatidine, lafutidine, lavoltidine, and niperotidine, etc.

What are the Similarities Between H1 and H2 Blockers?

• Both are types of antihistamines.
• They block the histamines receptors.
• 他们是用于treatment of human diseases.
• Both exist as neutral receptor antagonists or inverse agonists.

What is the Difference Between H1 and H2 Blockers?

H₁blockers refer to compounds that inhibit the activity of the H₁histamine receptors that occur throughout the vascular endothelial cells in the heart and central nervous system. On the other hand, H₂blockers refer to compounds that inhibit the activity of the H₂histamine receptors that mainly occur in the parietal cells of the gastric mucosa. Thus, this is the key difference between H1 and H2 blockers. Furthermore, H₁blockers were discovered in 1933, while H2 blockers were found much later in 1964.

The following infographic lists the differences between H1 and H2 blockers in tabular form.

Summary – H1 vs H2 Blockers

Currently, most people use antihistamines to treat allergies. The first generation of antihistamines was available from the 1930s. H1 and H2 blockers are two antihistamines. H1 blockers affect the nose, while H2 blockers affect the stomach. Furthermore, H₁blockers refer to compounds that inhibit the activity of the H₁histamine receptors, while H₂blockers refer to compounds that inhibit the activity of the H₂histamine receptors. Thus, this is the summary of the difference between H1 and H2 blockers.

Reference:

1. “Histamine H1 Receptor Antagonist.” ScienceDirect.
2. “H2 Blockers: MedlinePlus Medical Encyclopedia.” MedlinePlus, U.S. National Library of Medicine.

Image Courtesy:

1. “西替利嗪包装” Bybrett jordan(CC BY 2.0)via Flickr

2. “Cimetidine Structural Formula V.1” By Jü – Own work (CC0) via Commons Wikimedia