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D&T 3 test 2 > Histamine and Antihistamine > Flashcards

Histamine and Antihistamine Flashcards

1
Q

what is histamine synthesized from? what enzyme is used

A

histidine

- histidine decarboxylase (HDC)

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2
Q

Where is histamine predominately synthesized and stored

A

MAST CELLS

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3
Q

Where is histamine synthesize/stored in non-mast cell sites

A
  1. gastric enterochromaffin-like (ECL) cells
  2. epidermis
  3. CNS neurons
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4
Q

what does histamine get metabolized into

A
  1. N-methylhistamine

2. imidazole acetic acid

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5
Q

what converts N-methylhistamine into N-methylimidazoleacetic acid

A

monoamine oxidase (MAO)

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6
Q

When is histamine released

A

sensitized cells in response to allergen

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7
Q

what are other substances that release histamine from mast cells

A

CURARE
MORPHINE
venoms
inflammatory mediators

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8
Q

what releases histamine from gastric ECL cells

A

ACETYLCHOLINE (Ach) AND GASTRIN

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9
Q

How does histamine work in the CNS

A

acts as a neurotransmitter

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10
Q

Where is H1 receptors usually found

A

smooth muscle
endothelium
brain

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11
Q

Where is H2 receptor usually found

A

gastric mucosa
cardiac muscles
mast cells
brain

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12
Q

what are post-receptor mechanism for H1

A

Gq
IP3
increase DAG

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13
Q

What is a partially selective antagonist for H2 receptor

A

Ranitidine

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14
Q

what is a partially selective agonist for H1 receptor

A

2-CH3-histamine

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15
Q

what is the post-receptor mechanism for H2 receptor

A

Gs

increase cAMP

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16
Q

what is the partial selective agonist for H2 receptor

A

Dimaprit

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17
Q

what is the partially selective antagonist for H1 receptor

A

Chlorpheniramine

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18
Q

What receptor is located in blood vessels

A

H1 receptor

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19
Q

how does histamine directly impact blood vessels

A
  • Vasodilation
  • decrease TPR, BP
  • flushing
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20
Q

how does histamine indirectly impact blood vessels

A
  • release of endothelium-derived NO (nitric oxide) and PGI2 (rapid and short lived)
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21
Q

what histamine receptor is found in the capillaries

A

H1

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22
Q

how does histamine impact capillary permeability? impact?

A

increases permeability

causes edema

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23
Q

what histamine receptor works on the lungs

A

H1

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24
Q

histamine impact on lungs

A

bronchoconstriction ( especially asthmatics)

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25
Q

what histamine receptor works on gastric mucosa

A

H2

26
Q

histamine impact of gastric mucosa

A

increase acid secretion from parietal cells

27
Q

what receptor works on cutaneous sensory nerve endings

A

H1

28
Q

histamine impact on cutaneous sensory nerve endings

A

Pruritus ( epidermis)

pain and itching ( dermis)

29
Q

what receptor works in brain

A

H1

30
Q

what are histamine effects in CNS

A

Neurotransmitter

- increases wakefulness and inhibits appetite

31
Q

what receptor is involved in the triple response

A

H1

32
Q

what is the triple response

A
  1. red spot - vasodilation
  2. Wheal - increase capillary premeability
  3. Flare - axon reflex, vasodilation
33
Q

Name a physiological antagonist? when is it used?

A

epinephrine

- systemic anaphylaxis

34
Q

how do histamine release inhibitors work?

A

antigen-IgE interaction

35
Q

how do histamine receptor antagonists work

A

competitively antagonize on smooth muscle cells

36
Q

how do H1 receptor antagonists work

A

reversible competitive antagonist specifically at H1 receptors

37
Q

Name the 1 st generation histamine antogonists

A

Chlorpheniramine
Diphenhydramine
Hydroxyzine
Promethazine

38
Q

Name the second generation histamine antagonist

A

Cetirizine
Loratadine
Fexofenadine

39
Q

which first generation histamine antagonist has the greatest CNS sedation and antimuscarinic activity

A

Promethazine

40
Q

first generation H1 receptor histamine antagonist enter what part of the body rapidly

A

CNS

41
Q

who metabolizes Loratadine

A

Cyp3A4

42
Q

How does H1 receptor antagonist impact vasodilation?

A

inhibits it

43
Q

How does H1 receptor antagonist impact permeability

A

strongly blocks

44
Q

How does H1 receptor antagonist impact increased heart rate

A

partially block

45
Q

How does H1 receptor antagonist impact bronchoconstriction

A

reduced a little

46
Q

How does H1 receptor antagonist impact acid secretion

A

do not suppress

47
Q

How does H1 receptor antagonist impact pruritus

A

some relief

48
Q

How does H1 receptor antagonist impact flare and itching

A

suppresses both

49
Q

what is the antimuscarinic effect of H1 antagonists

A

inhibit responses to acetylcholine that are mediated by muscarinic receptors

50
Q

which H1 antagonists have anti-muscarinic effects

A
  • Promethazine strongest

- second generation have no effect

51
Q

which H1 antagonists are best at combating motion sickness

A

Promethazine

52
Q

what are 4 major adverse effects of H1 antagonist and class causes each ADR

A
  1. CNS stimulation
  2. CNS depression - 1 generation and Cetirizine
  3. antimuscarinic effects - 1st generation
  4. GI - 1st generation
53
Q

CNS depression from 1 st generation and Cetirizine is potentiated by what

A

alcohol and CNS depressants

54
Q

what is the pharmacokinetics for 2nd generation

A

poorly distributed to CNS

55
Q

what are 4 main therapeutic uses for histamine antagnoists

A
  • treat acute exudative allergy (hay fever, rhinitis)
  • bronhcial asthma ( not sole therapy)
  • systemic anaphylaxis ( epinephrine)
  • motion sickness and induce sedation ( 1st generation)
56
Q

Name 3 H2 receptor antagonists

A

Cimetidine
Ranitidine
Famotidine

57
Q

how do H2 antagonists work

A

competitive antagonist at H2 receptor

58
Q

what are the effects of H2 antagonists

A

decrease gastric acid secretion

59
Q

what are adverse effects of H2 antagonists

A

Headache
GI
Fatigue, drowsiness

60
Q

how is H2 antagonists excreted

A

renal- reduce dose in renal disease

61
Q

what are drug interactions for H2 antagonists

A

Cimetidine inhibits cytochrome P450

62
Q

what is a therapeutic use for H2 antagonist

A
  1. promote healing of peptic ulcer and duodenal ulcer
  2. uncomplicated GERD
  3. prophylaxis of stress ulcer

D&T 3 test 2 (14 decks)

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