Podcast
Questions and Answers
Which enzyme is responsible for the formation of histamine?
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?
Which type of histamine receptor is responsible for smooth muscle contraction of the gastrointestinal (GI) tract?
- H1 (correct)
- H3
- H2
- H4
What is the main effect of histamine binding to H2 receptors?
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?
Which cells contain the highest number of mast cells for immune function?
What is the main effect of circulating histamine acting on H1 receptors on endothelial cells?
What is the main effect of circulating histamine acting on H1 receptors on endothelial cells?
What does stimulation of H3 auto receptors by histamine cause?
What does stimulation of H3 auto receptors by histamine cause?
What is the triple response to histamine?
What is the triple response to histamine?
What is the main effect of histamine binding to H1 receptors in the airway smooth muscle?
What is the main effect of histamine binding to H1 receptors in the airway smooth muscle?
Which type of antihistamine is known to enter the brain and cause sedation?
Which type of antihistamine is known to enter the brain and cause sedation?
What is the primary reason for not taking sedating antihistamines in combination with other depressants or alcohol?
What is the primary reason for not taking sedating antihistamines in combination with other depressants or alcohol?
Which antihistamine is considered non-sedating and cardiac safe?
Which antihistamine is considered non-sedating and cardiac safe?
What is the primary mechanism of action of non-sedating antihistamines?
What is the primary mechanism of action of non-sedating antihistamines?
Which type of allergic reaction is associated with the formation of IgE antibodies and involves sensitization of tolerance pathways?
Which type of allergic reaction is associated with the formation of IgE antibodies and involves sensitization of tolerance pathways?
Which drug is known to raise the QT interval and is not considered cardiac safe?
Which drug is known to raise the QT interval and is not considered cardiac safe?
Which receptor is primarily responsible for mediating the itch sensation?
Which receptor is primarily responsible for mediating the itch sensation?
What is the duration of action of sedating antihistamines?
What is the duration of action of sedating antihistamines?
Which drug is used in the treatment of both insomnia and as an enhancer for the effects of analgesics?
Which drug is used in the treatment of both insomnia and as an enhancer for the effects of analgesics?
What is the specific allergic reaction that involves the activation of Th2-driven pathways and the formation of IgE antibodies?
What is the specific allergic reaction that involves the activation of Th2-driven pathways and the formation of IgE antibodies?
Which antihistamine is known for its limited crossing of the blood-brain barrier and high affinity for P-glycoprotein?
Which antihistamine is known for its limited crossing of the blood-brain barrier and high affinity for P-glycoprotein?
Which antihistamine is considered a 'dirty drug' with many side effects, including antimuscarinic effects and contraindications with sedating agents and CNS depressants?
Which antihistamine is considered a 'dirty drug' with many side effects, including antimuscarinic effects and contraindications with sedating agents and CNS depressants?
Flashcards
Histamine formation
Histamine formation
Histamine is produced by the enzyme histidine decarboxylase.
H1 receptor effect (GI)
H1 receptor effect (GI)
Histamine binding to H1 receptors causes smooth muscle contraction in the digestive tract.
H2 receptor function
H2 receptor function
Histamine binding to H2 receptors primarily stimulates stomach acid production.
Mast cells & immunity
Mast cells & immunity
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H1 receptor & increased permeability
H1 receptor & increased permeability
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H3 auto-receptor effect
H3 auto-receptor effect
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Histamine triple response
Histamine triple response
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H1 receptor & bronchoconstriction
H1 receptor & bronchoconstriction
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Sedating antihistamines caution
Sedating antihistamines caution
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Non-sedating antihistamines action
Non-sedating antihistamines action
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Type I hypersensitivity
Type I hypersensitivity
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Anaphylaxis cause
Anaphylaxis cause
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Tertiary antihistamines risk
Tertiary antihistamines risk
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H1 receptor and itch
H1 receptor and itch
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Sedating antihistamine duration
Sedating antihistamine duration
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Diphenhydramine uses
Diphenhydramine uses
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Cetirizine and blood-brain barrier
Cetirizine and blood-brain barrier
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Chlorpheniramine and side effects
Chlorpheniramine and side effects
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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.
