Antihistamines Flashcards Preview

Pharmacology Test #5 > Antihistamines > Flashcards

Flashcards in Antihistamines Deck (38)
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1

Distribution of mast cells

high numbers in the skin, nose, mouth, lungs, and intestinal mucosa

2

Histamine is complexed with

sulfated-polysaccharides, heparin sulfate, chondroitin sulfate, and proteases

3

Where is the non-mast cell histamine located?

nerve terminals in some areas of the brain (NT) and in the fundus of the stomach (specialized cells store histamine for stimulation of acid secretion)

4

Causes of histamine release from mast cells and basophils

1. Antigen mediated binding of antigen to antibodies bound to IgE on the cell surface
2. Non-antigen mediated thermal or mechanical stress, cytotoxic agents (venoms/drugs)

5

What kind of receptors are histamine receptors?

G-protein coupled

6

Where are H1 receptors distributed?

distributed throughout CV, respiratory system, and G.I. smooth muscle

7

The H1 receptor is linked to what pathway?

linked to the phosphoinositol pathway, activation causes contraction of smooth muscle

8

What is the H1 receptor also linked to?

also linked to vasodilation and stimulation of sensory nerves

9

Where is the H2 receptor distributed?

distributed in the CV system, GI smooth muscle and stomach

10

What is the H2 receptor linked to?

linked to relaxation of vascular smooth muscle and gastric secretion

11

Where are H1 and H2 receptors colocalized?

vascular smooth muscle and endothelium

12

Where are H3 receptors located?

mainly in the CNS; autoreceptor in neurons that use histamine as a neurotransmitter

13

What are H3 receptors linked to?

linked to inhibition of neurotransmitter releases

14

Where are H4 receptors located?

located on mast cells, basophils and eosinophils

15

What are H4 receptors linked to?

linked to histamine-induced chemotaxis; promising target for future antiinflammatory drugs

16

What does histamine do to the cardiovascular system?

Causes a moderate increase in rate and force of contraction of the heart; H2 receptors causes an increased in SA conduction; reflex tachycardia

17

What does histamine do to the respiratory system?

H1 mediated constriction of bronchial smooth muscle

18

What does histamine do to acid release in the stomach?

H2 mediated release from parietal cells in the stomach

19

What happens with histamine and anaphylaxis?

hypotension and loss of fluid to the interstitial space; lowers effective blood volume; swelling

20

Triple response that occurs when you inject histamine into the skin

1. red spot at the point of injection (immediate)
2. red flare radiating ~ 1 cm from injection site (~10s)
3. wheal (raised welt) at site of injection (1-2 min)

21

Skin pathologies caused by histamine

1. Urticaria (hives, rash, edematous welts
2. Dermatographia (redness or welt with mechanical stimulation
3. Flushing (erythema, redness in skin due to vasodilation)

22

H1 receptor antagonists are referred to as

antihistamines

23

H2 receptor antagonists are referred to as

acid blockers

24

First generation antihistamines

Brompheniramine, cyproheptadine, diphenhydramine, promethazine, hydroxyzine, pyrilamine

25

What can happen when children take H1 receptor antagonists?

paradoxical excitation in children at normal doses

26

What happens with antihistamines at high doses?

CNS stimulation at high doses

27

The most sedative antihistamines

ethanolamines and phenothiazies
(ex. diphenhydramine and promethazine)

28

OTC sleep aids

diphenhydramine: Sominex and Nytol

29

Second generation H1 antagonists

Loratadine, desloratadine, fexofenadine, citirizine, levocetirizine

30

How are second generation H1 antagonists different from first generation H1 antagonists?

decreased lipid solubility, little or no sedation, no anti-muscarinic activity, no anti-emetic activity, no anti-motion sickness activity