Histamine Functions and Effects Quiz
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Questions and Answers

What is the primary role of histamine in the body?

  • Stimulates neurotransmitter release
  • Regulates blood sugar levels
  • Involved in inflammatory and anaphylactic reactions (correct)
  • Promotes muscle contraction

What characterizes the 'red spot' observed after intradermal administration of histamine?

  • An effect from kinins and prostaglandins
  • A result of allergenic response
  • A direct vasodilatory effect from H1-mediated NO production (correct)
  • A response related to immune cell activation

Which of the following effects is associated with large systemic doses of histamine?

  • Decreased heart rate
  • Profound vascular changes similar to shock (correct)
  • Muscle spasms and rigidity
  • Increased appetite and metabolism

What is the 'flush' or 'flare' response following histamine administration attributed to?

<p>Release of other mediators such as kinins and prostaglandins (A)</p> Signup and view all the answers

When was histamine first synthesized and identified as a natural constituent of mammalian tissues?

<p>1907 for synthesis, 1927 for identification (A)</p> Signup and view all the answers

What is the mechanism of action for H1 receptor antagonists?

<p>They act as competitive inhibitors of histamine. (D)</p> Signup and view all the answers

Which of the following is a 1st generation H1 receptor antagonist?

<p>Diphenhydramine HCl (Benadryl) (D)</p> Signup and view all the answers

Which type of receptor does Famotidine act on as an antagonist?

<p>H2 receptors (D)</p> Signup and view all the answers

What can H1 receptor antagonists be indicated for?

<p>Anaphylaxis (C)</p> Signup and view all the answers

Which of the following H2 receptor antagonists has been withdrawn from the market?

<p>Ranitidine (Zantac) (D)</p> Signup and view all the answers

Which H3 receptor antagonist is FDA-approved for narcolepsy?

<p>Pitolisant (Wakix) (B)</p> Signup and view all the answers

What type of receptors do investigational agents for inflammatory diseases target?

<p>H4 receptors (B)</p> Signup and view all the answers

Which H2 receptor antagonist was withdrawn from the market per the FDA in April 2020?

<p>Ranitidine (Zantac) (A)</p> Signup and view all the answers

What is the primary use of H3 receptor antagonists like Pitolisant?

<p>Orphan drug for narcolepsy (C)</p> Signup and view all the answers

Which symptom is associated with activation of H1 receptors?

<p>Edema (D)</p> Signup and view all the answers

Which subtype of histamine receptor is implicated the most in mediating allergy symptoms?

<p>H1 receptor (D)</p> Signup and view all the answers

Which of the following is true regarding the pharmacology of the 2nd generation H1 receptor antagonists?

<p>They have a longer half-life and fewer CNS effects. (C)</p> Signup and view all the answers

Which of the following accurately reflects the mechanism of action for anti-histamine agents?

<p>They block histamine from binding to its receptors. (C)</p> Signup and view all the answers

Which ocular antihistamine is used in the treatment of allergic conjunctivitis?

<p>Azelastine (D)</p> Signup and view all the answers

What is the proposed role of H4 receptor antagonists in clinical therapy?

<p>As investigational agents for inflammatory diseases (B)</p> Signup and view all the answers

What is one common use of first-generation H1 receptor antagonists?

<p>Motion sickness (B)</p> Signup and view all the answers

Which pharmacological effect is NOT associated with first-generation agents?

<p>Inhibition of gastric acid secretion (C)</p> Signup and view all the answers

Which of the following is a side effect unique to first-generation H1 receptor antagonists due to their ability to cross the blood-brain barrier?

<p>Sedation (C)</p> Signup and view all the answers

Which first-generation antihistamine is commonly used for allergic reactions?

<p>Diphenhydramine HCl (B)</p> Signup and view all the answers

Which indication is NOT associated with the use of Cyproheptadine?

<p>Nausea and vomiting (B)</p> Signup and view all the answers

What caution is noted for the use of first-generation agents in elderly patients?

<p>Increased risk of sedation (D)</p> Signup and view all the answers

Which of the following conditions is specifically indicated for the use of Doxepin HCl?

<p>Psychotic depressive disorders (B)</p> Signup and view all the answers

Which generation of antihistamines includes agents like Benadryl and Chlorpheniramine?

<p>First generation (B)</p> Signup and view all the answers

Which generation of H1 receptor antagonists primarily mediates sedating effects in the central nervous system?

<p>1st generation (A)</p> Signup and view all the answers

What is the primary mechanism through which 2nd generation H1 receptor antagonists are metabolized?

<p>CYP enzyme metabolism (C)</p> Signup and view all the answers

What is the effect of Olopatadine as a topical H1 receptor antagonist?

<p>Slow rate of dissociation (D)</p> Signup and view all the answers

Which of the following is a pro-drug that gets converted into an active drug by CYP 3A4?

<p>Terfenadine (D)</p> Signup and view all the answers

What are the primary indications for using Azelastine as a topical H1 receptor antagonist?

<p>Rhinitis and conjunctival congestion (A)</p> Signup and view all the answers

Which of the following H1 receptor antagonists is noted for its mast cell stabilizing properties?

<p>Ketotifen (B)</p> Signup and view all the answers

What is a notable characteristic of Levocetirizine compared to its racemate?

<p>It is an R-enantiomer of cetirizine. (A)</p> Signup and view all the answers

Which H1 receptor antagonists are commonly available in both nasal spray and ophthalmic formulations?

<p>Azelastine and Olopatadine (D)</p> Signup and view all the answers

What is the primary distinction between memorization and knowledge?

<p>Knowledge involves deeper understanding of concepts. (B)</p> Signup and view all the answers

What should a student do if a concept does not make sense?

<p>Try to find the answer using available resources. (D)</p> Signup and view all the answers

Which method is recommended for contacting faculty for clarification on concepts?

<p>Email them to schedule an appointment. (A)</p> Signup and view all the answers

What is one suggested resource for literature search mentioned in the content?

<p>PubMed. (B)</p> Signup and view all the answers

What is the significance of understanding connections between concepts?

<p>It enhances comprehension and application of concepts. (A)</p> Signup and view all the answers

What is the best strategy for utilizing textbooks according to the content?

<p>Choose required textbooks for fundamental concepts and recommended ones for deeper insights. (D)</p> Signup and view all the answers

What is a potential consequence of relying solely on memorization?

<p>Limited understanding of intended concepts. (A)</p> Signup and view all the answers

Which of the following is NOT a suggested study resource?

<p>Social media platforms. (C)</p> Signup and view all the answers

Flashcards

Histamine

A naturally occurring chemical that acts as a neurotransmitter and inflammatory mediator. It's involved in various physiological processes such as allergic reactions, digestion, and sleep.

Histamine Receptor

A type of cell receptor that binds histamine. There are four main subtypes: H1, H2, H3, and H4.

H1 Receptor Antagonists

Drugs that block or antagonize the effects of histamine by binding to H1 receptors, preventing histamine from activating them.

1st Generation H1 Receptor Antagonists

This group consists of older H1 receptor antagonists with varying degrees of sedation, often used to manage allergies and other conditions like anxiety. They are not as selective as newer antihistamines.

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2nd Generation H1 Receptor Antagonists

Newer H1 receptor antagonists generally have less sedation and can be more selective for H1 receptors compared to older antihistamines. They are commonly prescribed for allergies.

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H2 Receptor Antagonists

Drugs that block the effects of histamine by targeting H2 receptors, commonly used to manage ulcers and other digestive issues.

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H3 Receptor Antagonists

Drugs that block the effects of histamine by binding to H3 receptors. Used to treat narcolepsy, which is a sleep disorder involving excessive daytime sleepiness.

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H4 Receptor Antagonists

Drugs that block the effects of histamine by binding to H4 receptors, currently in development for inflammatory conditions, but not yet widely used.

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What is Histamine?

Histamine is a naturally occurring compound found in plants, animals, and humans. It is an autacoid, a hormone-like substance, that plays a crucial role in inflammatory and allergic reactions.

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What is the Triple Response?

The triple response is a series of localized reactions that occur after intradermal injection of histamine. It includes a red spot due to direct vasodilation, a flush or flare due to the release of other mediators like kinins and prostaglandins, and a wheal or edema due to increased vascular permeability.

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Why is Histamine a significant discovery?

Histamine is the first autacoid discovered, meaning it was the first hormone-like substance identified to be naturally produced by the body.

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What causes the 'red spot' in the Triple Response?

The "red spot" in the triple response is a direct result of histamine's vasodilatory effect, mediated by the H1 receptor. This effect leads to increased blood flow in the area, resulting in redness.

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What contributes to the 'flush' or 'flare' in the Triple Response?

The "flush" or "flare" in the triple response is caused by the release of other inflammatory mediators like kinins and prostaglandins. These substances contribute to the spreading redness and heat sensation.

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H1 Receptor

A type of cell surface receptor that plays a crucial role in allergic reactions and inflammation. It's found in various tissues including endothelium and smooth muscle, and is responsible for triggering histamine-mediated responses like itching, sneezing, and swelling.

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Diphenhydramine (Benadryl), Chlorpheniramine, Cyproheptadine

Examples of first-generation H1 receptor antagonists. They are commonly use for allergies, and some also have applications in other conditions like anxiety.

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Cetirizine (Zyrtec), Loratadine (Claritin), Fexofenadine (Allegra)

Examples of second-generation H1 receptor antagonists known for their effectiveness in treating allergies, but often associated with fewer side effects.

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Levocetirizine (Xyzal), Desloratadine (Clarinex)

Examples of 3rd generation H1 Receptor Antagonists.

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What are H1 Receptor Antagonists useful for?

They are most effective in the treatment of allergies.

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Give some examples of H1 receptor antagonists.

Terfenadine, Cetirizine, Loratadine, Fexofenadine

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What are topical H1 Receptor Antagonists used for?

They are typically used for seasonal allergies.

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Give some examples of topical H1 receptor antagonists.

Azelastine, Olopatadine, Ketotifen, Emedastine

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What are common examples of topical H1 receptor antagonists for nasal allergies?

Azelastine and Olopatadine are commonly used for nasal allergies.

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What are H1 Receptor Antagonists?

Drugs that work by blocking the action of histamine at H1 receptors.

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Understanding vs. Memorization

Understanding a concept means grasping its relationships to other ideas, not just memorizing facts. True understanding requires deeper analysis and application.

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Resource for Clarification

If a concept is unclear, research it using online resources like the South College Library (http://library.south.edu/).

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Contacting Faculty

Contacting faculty via email first is the best way to schedule an appointment, ensuring they allot time to discuss your questions thoroughly.

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Canvas iMCP3 Resources

Canvas iMCP3 provides study resources, videos, and illustrations for learning, with durations ranging from 1 to 8 minutes.

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South College Library Resources

The South College Library's online resources include SOP guidelines and databases like AccessPharmacy, Micromedex, and Lexicomp.

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Literature Search

PubMed and Discover Search are available on the South College Library website for literature searching.

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Required Textbooks (Pharmacology)

Basic and Clinical Pharmacology by Katzung is a required textbook, supplemented by Goodman and Gilman's Medicinal Chemistry and Gilman's Pharmacological Basis of Therapeutics.

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Recommended Resources (NAPLEX)

RxPrep Course Review for NAPLEX is a recommended resource for preparing for the North American Pharmacist Licensure Examination.

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First-generation H1 receptor antagonists

First-generation H1 receptor antagonists are a class of drugs that work by blocking histamine from binding to its receptor, H1. The first generation of H1 receptor antagonists are used to manage allergic reactions, motion sickness, insomnia, anxiety, itching, vertigo, nausea, vomiting, post-operative pain, and psychotic depressive disorders.

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Side effects of first-generation H1 receptor antagonists

First-generation H1 receptor antagonists can readily cross the blood-brain barrier, leading to significant anti-cholinergic side effects such as drowsiness, dizziness, blurred vision, and confusion, especially in elderly patients.

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Diphenhydramine HCl (Benadryl)

Diphenhydramine HCl, commonly known as Benadryl, is a widely available first-generation H1 receptor antagonist used to treat allergic reactions, motion sickness, insomnia, and Parkinsonism. Due to its sedative effects, it is often used to promote sleep.

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Hydroxyzine HCl (Vistaril, Atarax)

Hydroxyzine HCl, also known as Vistaril or Atarax, is another first-generation H1 receptor antagonist. It is used for anxiety, itching, allergic rhinitis, and sedation. It is also used for motion sickness.

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Promethazine HCl (Phenergan)

Promethazine HCl, marketed as Phenergan, is a first-generation H1 receptor antagonist primarily used for motion sickness, vertigo, and nausea/vomiting. It is often used for postoperative pain management and sometimes for sedation.

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Cyproheptadine HCl

Cyproheptadine HCl, used for allergic reactions and anaphylaxis, is also prescribed off-label to treat loss of appetite and serotonin syndrome.

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Doxepin HCl (Sinequan)

Doxepin HCl, marketed as Sinequan, is a tricyclic dibenzoxazepine used for anxiety, insomnia, and psychotic depressive disorders. It is a first-generation H1 receptor antagonist, but it has a unique chemical structure compared to other traditional antihistamines.

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Pregnancy contraindication for first-generation H1 receptor antagonists

First-generation H1 receptor antagonists are often contraindicated in pregnant women due to potential adverse effects on the fetus.

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Study Notes

On-Ground and Hybrid In-Class Patient Cases

  • Cases will be released by Wednesday.
  • Participate the entire duration for a response rate of >90% on questions.
  • On-ground session is Thursday, January 16th at 8:30 AM.
  • Hybrid session is Friday, January 17th at 8:30 AM.

Pharmacology of Histamine and Antihistamines

  • Dr. Maha Abdalla, PharmD, PhD, RPh is the Associate Professor of Pharmaceutical Sciences.
  • Email: [email protected]
  • Office Room: 276
  • Phone: (865) 288-5837
  • Office Hours: Tuesday and Thursday 9 AM - 12 PM and by appointment.

Histamine and Antihistamines - Big Picture

  • Histamine: Biosynthesis & Metabolism
  • Histamine Receptors: GPCR (G protein-coupled receptors): H1, H2, H3, and H4
  • H1 Receptor Antagonists:
    • 1st generation: Diphenhydramine HCl (Benadryl), Chlorpheniramine, Cyproheptadine. Various indications including CNS disorders. Hydroxyzine HCL (Vistaril, Atarax), Promethazine HCl (Phenergan), Doxepin HCl (Sinequan), Cyproheptadine, Diphenhydramine
    • 2nd generation: Cetirizine HCl (Zyrtec), Piperidines: Loratadine (Claritin)
    • 3rd generation: Levocetirizine (Xyzal), Desloratadine (Clarinex), and Fexofenadine (Allegra)
  • H2 Receptor Antagonist: Famotidine (Pepcid, Zantac 360), cimetidine (Tagamet), nizatidine (Axid), Ranitidine (Zantac) -Note: all RX and OTC withdrawn from the market per the FDA (04/2020)
  • H3 Receptor Antagonist: Pitolisant (Wakix) – Orphan drug for narcolepsy (EDS, Cataplexy) –FDA approved 8/2019
  • H4 Receptor Antagonists: Investigational agents for inflammatory diseases

Lecture Objectives

  • Describe the role of histamine and anti-histamine agents.
  • Explain the different H-receptor subtypes, location, signaling pathways, and physiological effects.
  • Explain the mechanism of action for each drug class.
  • Describe potential adverse effects from drugs and how they function, why adverse events occur, and how drugs interact.
  • Demonstrate knowledge of applying therapeutic plans, evaluating patient cases, and interpreting patient values.
  • Discuss, compare, and contrast drugs within and across classes, including mechanisms of action, therapeutic indications, potential adverse effects, contraindications, drug interactions, and therapeutic implications.

Histamine Primer

  • A natural constituent in plants, animals, and humans acting as an autocoid.
  • Involved in inflammatory and anaphylactic reactions.
  • Local application causes swelling, redness, and edema.
  • Large systemic doses can have profound vascular effects similar to shock.
  • The Triple Response (intradermal administration of histamine) includes a localized red spot, a flush/flare, and a wheal.
  • The effect of histamine is due to direct vasodilation from histamine, H1-mediated NO production, and other mediators.

Histamine: Biosynthesis and Metabolism

  • Histamine is synthesized from L-histidine via L-histidine decarboxylase.
  • Stored and released by Mast cells, basophils in blood, in high concentrations in CSF, and in non-mast cell sites (epidermis, gastric mucus, and CNS neurons).
  • Pharmacodynamics – Histamine acts on 4 histamine receptors, which are all G protein coupled (GPCRs).
  • Metabolism has 1 pathway in central histamine with ring methylation by histamine-N-methyltransferase.
  • MAO-B in peripheral histamine, oxidative deamination by diamine oxidase.

Histamine - Receptors and Effects

  • Histamine is effective in the Lung (bronchoconstriction), Vascular wall, Peripheral nerves (vasodilation and edema), Heart, Stomach(stimulate gastric acid secretion), and CNS (neurotransmitter). Details are provided in the table about the effects and receptor subtype.

Histamine Receptors

  • All 4 histamine receptors are GPCRs.
  • H1 receptors are coupled to Gq/11, activate PLC-IP3-Ca2+ pathways → PKC, PLA2. Smooth muscle and endothelial cells, CNS. H1 receptors have an immunological response leading to allergy symptoms
  • H2 receptors are coupled to Gs and activate PKA. Found in gastric parietal cells, cardiac muscle, and mast cells. CNS H3 receptors are coupled to Gi and activate MAPK pathways. Found in CNS as presynaptic autoreceptors (feedback inhibition). H3R agonists decrease histamine release; H3R antagonists increase histamine release. H4 receptors are coupled to Gi and increase Ca++. Found in blood cells of hematopoietic lineage.

Topical H1 Receptor Antagonist

  • Indication: rhinitis, erythema and conjunctival congestion associated with seasonal allergic conjunctivitis.
  • Formulation: Nasal spray and/or ophthalmic solution.
  • Agents: Azelastine, Olopatadine (Patanol; Pataday; Patanase), Ketotifen, and Emedastine.

Top 200 Drugs

  • H1 Receptor Antagonists include: diphenhydramine, fexofenadine, loratadine, levocetirizine, cetirizine, azelastine, hydroxyzine, and hydroxyzine HCl. Antiemetic-Histamine Antagonist include promethazine.
  • H2 Receptor Antagonists include famotidine.

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Histamine Pharmacology - MA 2025 PDF

Description

Test your knowledge on the role and effects of histamine in the body. This quiz covers its primary functions, the physiological responses associated with its administration, and historical context regarding its synthesis. Challenge yourself with questions that delve into both the biochemical and clinical aspects of histamine.

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