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?

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

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

1907 for synthesis, 1927 for identification (A) Signup and view all the answers

What is the mechanism of action for H1 receptor antagonists?

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

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

Diphenhydramine HCl (Benadryl) (D) Signup and view all the answers

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

H2 receptors (D) Signup and view all the answers

What can H1 receptor antagonists be indicated for?

Anaphylaxis (C) Signup and view all the answers

Which of the following H2 receptor antagonists has been withdrawn from the market?

Ranitidine (Zantac) (D) Signup and view all the answers

Which H3 receptor antagonist is FDA-approved for narcolepsy?

Pitolisant (Wakix) (B) Signup and view all the answers

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

H4 receptors (B) Signup and view all the answers

Which H2 receptor antagonist was withdrawn from the market per the FDA in April 2020?

Ranitidine (Zantac) (A) Signup and view all the answers

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

Orphan drug for narcolepsy (C) Signup and view all the answers

Which symptom is associated with activation of H1 receptors?

Edema (D) Signup and view all the answers

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

H1 receptor (D) Signup and view all the answers

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

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

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

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

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

Azelastine (D) Signup and view all the answers

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

As investigational agents for inflammatory diseases (B) Signup and view all the answers

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

Motion sickness (B) Signup and view all the answers

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

Inhibition of gastric acid secretion (C) 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?

Sedation (C) Signup and view all the answers

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

Diphenhydramine HCl (B) Signup and view all the answers

Which indication is NOT associated with the use of Cyproheptadine?

Nausea and vomiting (B) Signup and view all the answers

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

Increased risk of sedation (D) Signup and view all the answers

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

Psychotic depressive disorders (B) Signup and view all the answers

Which generation of antihistamines includes agents like Benadryl and Chlorpheniramine?

First generation (B) Signup and view all the answers

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

1st generation (A) Signup and view all the answers

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

CYP enzyme metabolism (C) Signup and view all the answers

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

Slow rate of dissociation (D) Signup and view all the answers

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

Terfenadine (D) Signup and view all the answers

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

Rhinitis and conjunctival congestion (A) Signup and view all the answers

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

Ketotifen (B) Signup and view all the answers

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

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

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

Azelastine and Olopatadine (D) Signup and view all the answers

What is the primary distinction between memorization and knowledge?

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

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

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

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

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

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

PubMed. (B) Signup and view all the answers

What is the significance of understanding connections between concepts?

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

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

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

What is a potential consequence of relying solely on memorization?

Limited understanding of intended concepts. (A) Signup and view all the answers

Which of the following is NOT a suggested study resource?

Social media platforms. (C) Signup and view all the answers

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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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.