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Pharmacology III > Antihistamines > Flashcards

Antihistamines Flashcards

1
Q

Histamine is synthisized from histidine, and is found as granules in what two cell types?

A

Mast Cells

Basophils

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2
Q

What two body systems typically have histamine receptors?

A

brain, GI

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3
Q

Normally, histamine is complexed with proteases, heparin, or proteoglycans which ensure it is (active/inactive)

A

inactive storage

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4
Q

In the allergic reaction, T-Helper cells bind to a naive B-cell, which secretes _______ to plasma. ______ can then bind which receptors on mast cells/basophils to release histamine in the effector phase?

A

IgE

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5
Q

6 major effects of histamine

A 
SM contraction
Vasodilation
vascular permeability
platelet aggregation
complement activation
mucus secretion
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6
Q

IgE binds which receptors on mast cells/basophils?

A

Fc

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7
Q

An allergen forms what on which mast cell structures that results in activation?

A

allergen bridges IgE

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8
Q

The activated mast cells utilizes PK to increase concentrations of what two substances?

A

IP3 and Calcium

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9
Q

increased intracellular concentration of IP3 and Calcium activates ______, which has what 4 effects?

A

IP3 and Calcium activate PLA2

PLA2 increases platelet activating factor, leukotrienes, kinins, histamine release

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10
Q

The below have what effect on mast cells?


Contrast dyes

Organic bases

Morphine

d-TC, Succinylcholine

Many venoms

Scratching, cold, sun
A

Cause histamine release without sensitization (IgE)

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11
Q

Is the itching after morphine administration an allergic response? why or why not?

A

no… no IgE Abs to morphine.

Morphine causes direct histamine release

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12
Q

What effect does the H1 receptor have on endothelium?

A

activates NO

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13
Q

H1 receptor mediates the allergic response present on what 2 tissue types?

A

smooth muscle

endothelium

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14
Q

H1 receptor has what 2 effects on the brain?

A

wakefullness

appetite control

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15
Q

What three tissue types have the H1 receptor?

A

smooth muscle
endothelium
brain

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16
Q

What three cell types have the H2 receptor?

A

heart, brain, mast cells

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17
Q

The main function of the H2 receptor…

A

gastric acid secretion (via cAMP)

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18
Q

Which histamine receptor types cause vasodilation?

A

H1 and H2

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19
Q

Which histamine receptor types cause bronchospasm?

A

H1

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20
Q

In order for H2 receptors to exert vasodilatory effects, what concentration of histamine must be present?

A

high concentration

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21
Q

What are 3 major effects of histamine mediated vasodilation?

A
  1. decreased BP + reflex tachycardia
  2. capillary permeability
  3. edema, swelling
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22
Q

What effect does histamine have on the skin?

A

causes pruritis

23
Q

what is described below?

red spot via vasodilation

flare due to out axon-reflexes

wheal in 2-3 minutes due to capillary permeability

A

triple response

24
Q

What is the first sign of histamine release?

A

burning/itching (esp. ears)

25
Q

Antihistamines are technically which type of drug?

A

inverse agonist (decrease transmitter activity)

26
Q

Why are antihistamines good for motion sickness and insomnia?

A

Blocks muscarinic receptors/anticholinergic properties

27
Q

Increased _______ blockade means more sedation

A

muscarinic

28
Q

Histamine has a ________ relationship with antihistamines, meaning __________ can overcome the blockade

A

competitive relationship

high concentration

29
Q

Why are 1st gen H1 antagonists more sedating than 2nd gen?

A

lipophilic, so enters brain to have anticholinergic effect

30
Q

The below have what effect?

diphenhydramine
doxylamine
hydroxyzine

A

Sedation

31
Q

The below have what effect?

Diphenhydramine
Dimenhydrinate

A

anti-motion sickness (M blocker)

32
Q

The below have what effect?

promethazine

A

anti-emetic/motion sickness

33
Q

What additional receptor does promethazine block that gives it an anti-emetic property?

A

D2 receptor blocker

34
Q

Diphenhydramine and histamine are structurally related to…

A

ACh

35
Q

Do 2nd gen H1 antagonists have anticholinergic effects? What does this mean for motion sickness?

A

no, not good for motion sickness

36
Q

Antihistamines are metabolized by _______ which may be _____ in chronic use

A

metabolism by CYP450

induced metabolism in chronic use

37
Q

Which three 2nd gen H1 blockers are excreted directly by the kidney?

A

cetirizine
levocetirizine
acrivastine

38
Q

cetirizine
levocetirizine
acrivastine

these drugs would be a good choice for which patients?

A

liver disease, multiple drugs

39
Q

cetirizine
levocetirizine
acrivastine

These drugs would be a bad choice for which patients?

A

impaired kidney function

40
Q

Antihistamines for allergic rhinitis and motion sickness have best effect when used…

A

prophylacticly

41
Q

1st gen antihistamines for sedation should be used _______ due to ________ development

A

occasionally, tolerance

42
Q

Which generation of H1 blocker will dry up secretions? why?

A

1st gen, anticholinergic

43
Q

what is an important S/E of 1st gen H1 blockers in the CNS?

A

decreased seizure threshold

44
Q

Beacuse of anticholinergic properties, 1st gen H1 receptors have what side effect?

A

dry mouth & and other anticholinergic SEs

45
Q

1st gen H1 blockers interact with…

A

CNS depressants

46
Q

2nd gen H1 blockers interact with…(4)

A

erythromycin
ketoconazole
cimetidine
grapefruit juice

47
Q

Children under _____ shouldn’t use any OTC cold or cough product…

A

under 4 yo

48
Q

OD of 1st gen H1 blockers is similar to…

A

atropine poisoning (blind as a bat, hot as a hare, red as a beet, mad as a hatter, etc)

49
Q

OD of newer 2nd gen H1 blockers …

A

sinus tachy

50
Q

OD of older 2nd gen H1 blockers …

A

cardiac arrhythmia

51
Q

this drug directly inhibits histamine release by stabilizing mast cells…

A

Cromolyn

52
Q

This drug inhibits histamine release directly and also blocks receptors

A

azelastine

53
Q

This 2nd gen H1 blocker may also inhibit histamine release

A

cetirizine

Pharmacology III (15 decks)

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