Antihistamines Flashcards Preview

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Flashcards in Antihistamines Deck (28):
1

Where are H1 receptors located?

  • Blood vessels
  • Smooth muscle of the airway and gastrointestinal tract
  • Heart
  • Central nervous system 

2

TRUE/FALSE

The H1 receptor is primarily associated with histamine-induced effects of pruritus, pain and increased vascular permeability. 

TRUE

The H1 receptor is primarily associated with histamine-induced effects of pruritus, pain and increased vascular permeability. 

3

TRUE/FALSE

Organs with H2 receptors include the gastric mucosa, uterus, heart, and central nervous system. 

TRUE

Organs with H2 receptors include the gastric mucosa, uterus, heart, and central nervous system. 

4

The major histamine effects of H2 receptors are _______ and ______. 

The major histamine effects of H2 receptors are increased gastric acid secretion and increased vascular permeability.

 

You can also see immunomodulatory changes such as alteration of lymphocyte proliferative responses, antibody synthesis and chemotaxis. 

5

TRUE/FALSE

The principal mechanism of action of compounds used for treatment of allergic skin disease in humans is histamine H2 receptor antagonism. 

FALSE

The principal mechanism of action of compounds used for treatment of allergic skin disease in humans is histamine H1 receptor antagonism

6

TRUE/FALSE

The following antihistamines may block serotonin receptors: 

hydroxyzine, cetirizine, cyproheptadine.

TRUE

The following antihistamines may block serotonin receptors: 

hydroxyzine, cetirizine, cyproheptadine.

7

TRUE/FALSE

There is sufficient evidence to make recommendations for oral antihistamines as part of the treatment of AD in human patients. 

FALSE

There is insufficient evidence to make recommendations for oral antihistamines as part of the treatment of AD in human patients. 

 Hoare et al., 2000 - AD consensus statement

8

What are the main side effects of antihistamines?

Sedation, anticholinergic effects, trembling, ataxia, hyperesthesia, hypersalivation, increased pruritus, panting, and excitation. 

9

What cardiac abnormality might you see in a dog on a non-sedating antihistamine?

Prolonged Q-T interval

Torsades de pointes

10

If you are going to notice a beneficial effect of an antihistamine for your patient, when will that be? 

A: 1-2 days

B: 7-14 days

C: 30+ days

D: 2-3 months 

If you are going to notice a beneficial effect of an antihistamine for your patient, when will that be? 

A: 1-2 days

B: 7-14 days

C: 30+ days

D: 2-3 months 

11

TRUE/FALSE

 Antihistamines are never additive or synergistic in their effects when used along with other medications such as EFA supplements or corticosteroids 

FALSE

 Antihistamines are additive or synergistic in their effects when used along with other medications such as EFA supplements or corticosteroids 

12

How is histamine synthesized?

Histidine decarboxylation

A image thumb
13

Where are H3 receptors found? Is this an exclusive location?

CNS! Yes! 

H3 = CNS only

14

What tissue contains more histamine receptors than any other?

Venule endothelia

15

Why do first generation H1-antihistamines induce sedation?

If an H1-antihistamine crosses the BBB, it will inhibit H1 receptors on neurons that project from the tuberomammillary nucleus; drowsiness will ensue since these neurons have a role in the sleep-wake cycle 
 

16

Diphenhydramine

First or second generation?

Class? 

Agonist or antagonist?

First generation H1-antihistamine; ethanolamine class of antihistaminergic agents; inverse agonist

Also - anti-cholinergic effects (mACh; competitive antagonist), sodium channel blocker (local anesthetic) 

17

What are the contraindications for basically all H1-antihistamines?

Hyperthyroidism, cardiovascular disease, hypertension, glaucoma, prostatic hypertrophy, pyeloduodenal or bladder neck obstruction, hepatic disease, pregnancy, lactation; 2-week withdrawal for IDAT 

18

What are the side effects of virtually all H1-antihistamines?

CNS depression (lethargy, somnolence); anticholinergic effects (dry mouth, urinary retention, constipation) 

19

What are the drug interactions of virtually all H1-antihistamines?

  • Anticholinergic drugs (tricyclic antidepressants) – potentiates effects
  • Anticoagulants (heparin) – counteracts effects
  • Epinephrine – enhances effects
  • Monoamine oxidase inhibitors (amitraz, amitriptyline) – potentiates
  • Other CNS depressants – potentiates 

20

What is an arrhythmia pattern that can be seen with diphenhydramine and loratidine?

Torsades de pointes is an arrhythmia that can be seen with diphenhydramine (blocks delayed rectifier potassium channel which prologues the Q1 interval)  

 

21

Chlorpheniramine maleate

First or second generation? 

Class of antihistamine?

Antagonist or agonist?

Chlorpheniramine maleate

FIRST GENERATION

ALKYLAMINE

RECEPTOR ANTAGONIST

 

22

CLEMASTINE

First or second generation? 

Class of antihistamine?

Antagonist or agonist?

CLEMASTINE

First generation

Ethanolamine 

Receptor antagonist

23

Cyproheptadine

First or second generation? 

Class of antihistamine?

Antagonist or agonist?

Cyproheptadine

First generation

Piperazine derivative 

Receptor antagonist

 

24

Hydroxyzine

First or second generation? 

Class of antihistamine?

Antagonist or agonist?

Hydroxyzine

First generation

Piperazine derivative 

Receptor antagonist

 

25

Certirizine (Zyrtec) 

First or second generation? 

Class of antihistamine?

Antagonist or agonist?

Certirizine (Zyrtec) 

Second generation

Piperazine derivative 

Receptor antagonist

 

26

Loratidine (Claritin)

First or second generation? 

Class of antihistamine?

Antagonist or agonist?

Loratidine (Claritin)

Second generation

Piperazine derivative

Receptor antagonist

 

27

Why would you use an H2-antihistamine?

GERD and peptic ulceration

Antihistamines for H2-receptors will decrease gastric acid secretion from parietal cells

28

Doxepin

Which histamine receptors does this medication act on?

H1 and H2