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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
what histamine receptor works on gastric mucosa
H2
26
histamine impact of gastric mucosa
increase acid secretion from parietal cells
27
what receptor works on cutaneous sensory nerve endings
H1
28
histamine impact on cutaneous sensory nerve endings
Pruritus ( epidermis) | pain and itching ( dermis)
29
what receptor works in brain
H1
30
what are histamine effects in CNS
Neurotransmitter | - increases wakefulness and inhibits appetite
31
what receptor is involved in the triple response
H1
32
what is the triple response
1. red spot - vasodilation 2. Wheal - increase capillary premeability 3. Flare - axon reflex, vasodilation
33
Name a physiological antagonist? when is it used?
epinephrine | - systemic anaphylaxis
34
how do histamine release inhibitors work?
antigen-IgE interaction
35
how do histamine receptor antagonists work
competitively antagonize on smooth muscle cells
36
how do H1 receptor antagonists work
reversible competitive antagonist specifically at H1 receptors
37
Name the 1 st generation histamine antogonists
Chlorpheniramine Diphenhydramine Hydroxyzine Promethazine
38
Name the second generation histamine antagonist
Cetirizine Loratadine Fexofenadine
39
which first generation histamine antagonist has the greatest CNS sedation and antimuscarinic activity
Promethazine
40
first generation H1 receptor histamine antagonist enter what part of the body rapidly
CNS
41
who metabolizes Loratadine
Cyp3A4
42
How does H1 receptor antagonist impact vasodilation?
inhibits it
43
How does H1 receptor antagonist impact permeability
strongly blocks
44
How does H1 receptor antagonist impact increased heart rate
partially block
45
How does H1 receptor antagonist impact bronchoconstriction
reduced a little
46
How does H1 receptor antagonist impact acid secretion
do not suppress
47
How does H1 receptor antagonist impact pruritus
some relief
48
How does H1 receptor antagonist impact flare and itching
suppresses both
49
what is the antimuscarinic effect of H1 antagonists
inhibit responses to acetylcholine that are mediated by muscarinic receptors
50
which H1 antagonists have anti-muscarinic effects
- Promethazine strongest | - second generation have no effect
51
which H1 antagonists are best at combating motion sickness
Promethazine
52
what are 4 major adverse effects of H1 antagonist and class causes each ADR
1. CNS stimulation 2. CNS depression - 1 generation and Cetirizine 3. antimuscarinic effects - 1st generation 4. GI - 1st generation
53
CNS depression from 1 st generation and Cetirizine is potentiated by what
alcohol and CNS depressants
54
what is the pharmacokinetics for 2nd generation
poorly distributed to CNS
55
what are 4 main therapeutic uses for histamine antagnoists
- treat acute exudative allergy (hay fever, rhinitis) - bronhcial asthma ( not sole therapy) - systemic anaphylaxis ( epinephrine) - motion sickness and induce sedation ( 1st generation)
56
Name 3 H2 receptor antagonists
Cimetidine Ranitidine Famotidine
57
how do H2 antagonists work
competitive antagonist at H2 receptor
58
what are the effects of H2 antagonists
decrease gastric acid secretion
59
what are adverse effects of H2 antagonists
Headache GI Fatigue, drowsiness
60
how is H2 antagonists excreted
renal- reduce dose in renal disease
61
what are drug interactions for H2 antagonists
Cimetidine inhibits cytochrome P450
62
what is a therapeutic use for H2 antagonist
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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