Histamines and Antihistamines Quiz

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Questions and Answers

Which enzyme is responsible for the formation of histamine?

Guanylyl cyclase

Nitric oxide synthase

Histidine decarboxylase (correct)

Phospholipase C

Which type of histamine receptor is responsible for smooth muscle contraction of the gastrointestinal (GI) tract?

H1 (correct)

What is the main effect of histamine binding to H2 receptors?

Reddening of the skin

Smooth muscle contraction of GI and bronchioles

Decreased histamine release from histaminergic neurons

Secretion of gastric acid in the stomach (correct)

Which cells contain the highest number of mast cells for immune function?

Lungs Signup and view all the answers

What is the main effect of circulating histamine acting on H1 receptors on endothelial cells?

Causing the release of NO from Nitric oxide synthase Signup and view all the answers

What does stimulation of H3 auto receptors by histamine cause?

Decreased histamine release from histaminergic neurons Signup and view all the answers

What is the triple response to histamine?

Reddening of the skin, surrounding flare, weal Signup and view all the answers

What is the main effect of histamine binding to H1 receptors in the airway smooth muscle?

Muscle contraction leading to bronchoconstriction Signup and view all the answers

Which type of antihistamine is known to enter the brain and cause sedation?

First-generation antihistamines Signup and view all the answers

What is the primary reason for not taking sedating antihistamines in combination with other depressants or alcohol?

Enhanced CNS depression Signup and view all the answers

Which antihistamine is considered non-sedating and cardiac safe?

Fexofenadine Signup and view all the answers

What is the primary mechanism of action of non-sedating antihistamines?

Blocking/inhibiting histamine actions at H1 receptors Signup and view all the answers

Which type of allergic reaction is associated with the formation of IgE antibodies and involves sensitization of tolerance pathways?

Type 1 allergic reaction Signup and view all the answers

Which drug is known to raise the QT interval and is not considered cardiac safe?

Terfenadine Signup and view all the answers

Which receptor is primarily responsible for mediating the itch sensation?

H1 receptors Signup and view all the answers

What is the duration of action of sedating antihistamines?

24-30 hours Signup and view all the answers

Which drug is used in the treatment of both insomnia and as an enhancer for the effects of analgesics?

Doxylamine Signup and view all the answers

What is the specific allergic reaction that involves the activation of Th2-driven pathways and the formation of IgE antibodies?

Type 1 allergic reaction Signup and view all the answers

Which antihistamine is known for its limited crossing of the blood-brain barrier and high affinity for P-glycoprotein?

Fexofenadine Signup and view all the answers

Which antihistamine is considered a 'dirty drug' with many side effects, including antimuscarinic effects and contraindications with sedating agents and CNS depressants?

Promethazine Signup and view all the answers

Study Notes

Histamine and its Effects

Histamine is formed by the enzyme histidine decarboxylase.
Histamine binding to H1 receptors causes smooth muscle contraction of the gastrointestinal (GI) tract.
The main effect of histamine binding to H2 receptors is gastric acid secretion.
Mast cells contain the highest number of immune cells for immune function.

Histamine Receptors

Histamine binding to H1 receptors on endothelial cells causes increased permeability and edema.
Stimulation of H3 auto receptors by histamine causes inhibition of histamine release.
The triple response to histamine is characterized by redness, wheal, and flare reactions.
Histamine binding to H1 receptors in the airway smooth muscle causes bronchoconstriction.

Antihistamines

Sedating antihistamines can enter the brain and cause sedation, and are not recommended to be taken with other depressants or alcohol.
Non-sedating antihistamines, such as loratadine, are considered cardiac safe and do not cause sedation.
The primary mechanism of action of non-sedating antihistamines is competitive inhibition of histamine binding to H1 receptors.

Allergic Reactions

Type I hypersensitivity reactions involve the formation of IgE antibodies and sensitization of tolerance pathways.
The specific allergic reaction that involves the activation of Th2-driven pathways and the formation of IgE antibodies is anaphylaxis.

Pharmacology

Tertiary antihistamines, such as terfenadine, are known to raise the QT interval and are not considered cardiac safe.
The H1 receptor is primarily responsible for mediating the itch sensation.
Sedating antihistamines have a duration of action of 4-6 hours.
Diphenhydramine is used in the treatment of both insomnia and as an enhancer for the effects of analgesics.
Cetirizine is known for its limited crossing of the blood-brain barrier and high affinity for P-glycoprotein.
Chlorpheniramine is considered a 'dirty drug' with many side effects, including antimuscarinic effects and contraindications with sedating agents and CNS depressants.

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Description

Test your knowledge of histamines and antihistamines with this quiz! Explore the formation, storage, and release of histamine, as well as its physiological effects. Delve into the role of mast cells and basophils, and learn about the action of antihistamines in combating histamine-related symptoms.