Histamines And Antihistamines

Question 1

Describe the synthesis of histamine

Answer 1

Histamine is synthesized by the decarboxylation of histidine by histidine decarboxylase

Question 2

How is histamine deactivated

Answer 2

It is deactivated by amine oxidase enzymes

Question 3

H2 receptor blockers are used mostly in

Answer 3

Inhibition of gastric acid secretion to treat GERD, gastritis and peptic Ulcer disease

Question 4

Example of H2 receptor blockers are

Answer 4

Ranitidine
Famotidine
Cimetidine

Question 5

Examples of first generation anti histamine

Answer 5

Chlorpheniramine
Diphenhydramine
Brompheniramine
Cyclizine

Question 6

Examples of second generation Antihistamine

Answer 6

Fexofenadine
Loratadine
Desloratadine
Azelastine

Question 7

To distinguish between first generation and second generation antihistamine you do it under the following heading

Answer 7

Sedation
Duration of action
AntiCholinergic action
CVS action
Drug/drug interactions

Question 8

Past Question
Pharmacological and organ system of histamine

Answer 8

Histamine primarily affects several organ systems in the body, including the respiratory system, cardiovascular system, gastrointestinal system, and skin.
Here are some of the organ system effects of histamine:

1. Respiratory System: Histamine can cause bronchoconstriction (narrowing of airways), leading to difficulty in breathing, wheezing, and shortness of breath.
2. Cardiovascular System: Histamine can dilate blood vessels, resulting in increased blood flow and lowered blood pressure. It can also cause a rapid heartbeat and flushing of the skin.
3. Gastrointestinal System: Histamine can stimulate the secretion of gastric acid in the stomach, leading to increased acid production. This may result in symptoms like acid reflux, heartburn, and stomach ulcers. H2
4. Skin: Histamine can trigger allergic reactions in the skin, causing redness, itching, swelling (hives), and in severe cases, it can lead to anaphylaxis. H1

These effects occur when histamine binds to specific receptors in the target organs, initiating a series of physiological responses. It’s important to note that individual responses to histamine can vary, and some people may be more sensitive to its effects than others.