miscellaneousHistamine and Antihistamines - A brief Overview

Histamine and Antihistamines – A brief Overview

-

Introduction

chemical structure of Histamine C5H9N3

Histamine is a biogenic amine found in many tissues, including mast cells, basophils, lymphocytes, neurons, and gastric enterochromaffin-like cells. It is an autacoid, a molecule secreted locally to increase or decrease the activity of nearby cells. Histamine is a major mediator of allergic and inflammatory processes and also has significant roles in the regulation of gastric acid secretion, neurotransmission, and immune modulation1.

Histamine Allergies or allergic diseases

Physiology of Histamine

Histamine is synthesized from the amino acid L-histidine. The enzyme histidine decarboxylase catalyzes the decarboxylation of histidine to 2-(4-imidazolyl)ethylamine, commonly known as histamine. The synthesis of histamine occurs in mast cells and basophils of the immune system, enterochromaffin-like (ECL) cells in the gastric mucosa, and certain neurons in the central nervous system (CNS) that use histamine as a neurotransmitter1.

Histamine acts directly on the blood vessels to dilate arteries and capillaries; this action is mediated by both H1- and H2-receptors. Capillary dilatation may produce flushing of the face, a decrease in systemic blood pressure, and gastric gland secretion, causing an increased secretion of gastric juice with high acidity. Increased capillary permeability accompanies capillary dilatation, producing an outward passage of plasma protein and fluid into the extracellular spaces, an increase in lymph flow and protein content, and the formation of edema2.

Pharmacology of Antihistamines

Antihistamines are synthetic drugs that selectively counteract the pharmacological effects of histamine3. They are not receptor antagonists but are inverse agonists, i.e., they produce the opposite effect on the receptor to histamine4, 5. Antihistamines block histamine at H1 receptors, inhibit smooth muscle constriction in blood vessels and the respiratory and GI tracts, and decrease capillary permeability, salivation, and tear formation6.

First-generation antihistamines are less effective than second-generation antihistamines and have unwanted side effects, particularly central nervous system and anti-cholinergic effects. Second-generation antihistamines are more efficacious and safe for the treatment of allergic disease4. Of the three drugs highlighted in this review, levocetirizine and fexofenadine are the most efficacious in humans in vivo5. However, levocetirizine may cause somnolence in susceptible individuals, while fexofenadine has a relatively short duration of action, requiring twice-daily administration for full all-round daily protection. Desloratadine is less efficacious, but it has the advantages of rarely causing somnolence and having a long duration of action4, 5.

Histamine and antihistamine medicine

Conclusion

Histamine plays a crucial role in various physiological and pathological processes. Antihistamines, particularly second-generation ones, have proven to be effective in managing conditions where histamine plays a detrimental role. Understanding the pharmacology of histamine and antihistamines can lead to the development of more effective therapeutic strategies for conditions such as allergies and inflammatory diseases.

Oh hi there 👋

Sign up to receive awesome content in your inbox, every month.

We don’t spam! Read our privacy policy for more info.

Oh hi there 👋

Sign up to receive awesome content in your inbox every month.

We don’t spam! Read our privacy policy for more info.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always seek the advice of a healthcare provider with any questions regarding a medical condition.

LEAVE A REPLY

Please enter your comment!
Please enter your name here

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Latest articles

Inflammatory Bowel Disease (IBD)

Introduction Inflammatory Bowel Disease (IBD) is a term that encompasses two main chronic conditions: Crohn's disease and ulcerative colitis. These...

Irritable Bowel Syndrome (IBS)

Introduction Irritable Bowel Syndrome (IBS) is a common gastrointestinal disorder characterized by a group of symptoms that typically occur together....

Gastroesophageal Reflux Disease (GERD)

Introduction Gastroesophageal Reflux Disease (GERD) is a chronic digestive disorder marked by the recurrent reflux of stomach contents, particularly gastric...

Peptic Ulcer Disease (PUD)

Introduction Peptic Ulcer Disease (PUD) is a gastrointestinal disorder characterized by sores or lesions in the lining of the stomach...

Helicobacter pylori Infection and Treatment

Introduction Helicobacter pylori (H. pylori) is a bacterium that infects the stomach lining and is a common cause of peptic...

Zollinger-Ellison Syndrome (ZES)

Zollinger-Ellison Syndrome (ZES) is a rare digestive disorder characterized by the development of one or more tumors, known as...

Helicobacter pylori Infection and Treatment

Introduction Helicobacter pylori (H. pylori) is a bacterium that infects the stomach lining and is a common cause of peptic...

Zollinger-Ellison Syndrome (ZES)

Zollinger-Ellison Syndrome (ZES) is a rare digestive disorder characterized by the development of one or more tumors, known as...

Miscellaneous

Pharmacology of Levocetirizine

Introduction Levocetirizine is a second-generation antihistamine that is used to treat symptoms associated with chronic allergic rhinitis and uncomplicated cases...

Pharmacology of Histamine and Antihistamines

Histamine, a pivotal mediator in various physiological and pathological processes, is synthesized from the amino acid L-histidine. This transformation...

You might also likeRELATED
Recommended to you

Pharmacology Mentor We would like to show you notifications for the latest news and updates.
Dismiss
Allow Notifications