Histamine flashcard for medical students;easy way to remember

Histamine

           Decarboxylation 

Histidine ➡️➡️➡️➡️➡️➡️Histamine

H1 Receptor 

Histamine

⬇️

H1 Receptor

⬇️

Vasodilation

⬇️

Hypotension

H4 receptor

• location-Heamatopoetic cells
• Histamine  ⇾ H4 receptor ⇾ Chemotaxis

H1  antagonist is two type

1st generation antihistaminics

Diphenhydramine

Hydroxyzine

Promethazine

2nd generation antihistaminic

Loratidine

cetrizine

Fexofenadine

Desloratidine

Levocetrizine

FAQ

Write the classification H2 anti histamines and give the mechanism of action of H2 antihistamines?

Ans-

Ranitidine

Cimetidine

Famotidine

Roxatidine

MOA;

These drugs reversibly block binding of histamine to H2 receptor present on Parietal cells of gastric mucosa .

These causes -decrease cyclic AMP➡️  decrese activity of H+/K+ proton pump ➡️ gastric acid secretion