Anti-histamines Part 1 Flashcards

1
Q

What is the histamine precursor?

A

Histidine

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2
Q

What enzyme converts histidine to histamine?

A

Histidine Decarboxylase

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3
Q

What are 4 functions of histamine?

A
  • immediate allergic and inflammatory reactions
  • gastric acid secretion
  • neurotransmission and neuromodulation
  • chemotactic factor for recruitment of neutrophils, eosinophils, basophils, monocytes, and lymphocytes
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4
Q

Where is histamine stored in the blood?

A

In basophils- preformed granules

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5
Q

Where is histamine stored in the tissue?

A

Mast cells

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6
Q

Where is histamine stored? (4 locations)

A
  • blood basophils
  • tissue mast cells
  • gastric mucosal cells
  • neurotransmitter vesicles
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7
Q

What does the Histamine 1 Receptor cause an increase in?

A

IP3/DAG

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8
Q

Which histamine receptors causes a decrease in cAMP?

A

H3 and H4

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9
Q

What receptor leads to an increased cAMP?

A

H2

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10
Q

What effects does histamine have in the cardiovascular system?

A
  • vasodilation of arterioles and precapillary sphincters via H1
  • increased vascular permeability via H1 (hives)
  • increased heart rate
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11
Q

What histamine receptor is involved in increased vascular permeability?

A

H1

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12
Q

What are the effects of histamine in the GI?

A

increased acid secretion via H2

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13
Q

What histamine receptor is involved in increasing gastric acid secretion?

A

H2

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14
Q

Which histamine receptor leads to bronchoconstriction?

A

H1

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15
Q

What are the nervous system effects of histamine?

A

stimulation of sensory nerve endings via H1

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16
Q

What cell types are involved in the wheal and flare reaction?

A

vasculature- dilation
endothelium- permeability –> edema
sensory nerve endings - red, irregular flare surrounds wheal (can have itching)

17
Q

What two mediators are increased with histamine to cause vasodilation?

A

Nitric oxide and prostaglandin

18
Q

What causes the edema with histamine?

A

Endothelial- H1 receptor

Contraction of endothelial cells which causes vascular permeability

19
Q

Chlorpheniramine

A

1st Gen H1 receptor competitive antagonist

20
Q

Diphenhydramine

A

1st Gen H1 receptor competitive antagonist

21
Q

What is the duration of 1st Gen H1 receptor competitive antagonists?

A

Short duration of 3-6 hours

22
Q

What effects are related to 1st Gen H1 receptor competitive antagonists?

A
anticholinergic
anti a-adrenergic : 
anti-serotonergic : anti seretonin effects
sedation
antiemetic- against vomiting and nausea
anti-motion sickness
23
Q

What drug class has a long duration of 12-24 hours?

A

2nd/3rd Gen H1 receptor competitive antagonists

24
Q

loratadine

A

2nd/3rd Gen H1 receptor competitive antagonists

25
fexofenadine
2nd/3rd Gen H1 receptor competitive antagonists
26
cetirizine
2nd/3rd Gen H1 receptor competitive antagonists
27
What is the difference in side effects between 1st Gen and 2nd/3rd Gen H1 receptor competitive antagonists?
2nd/3rd Gen H1 receptor competitive antagonists have LITTLE TO NO anticholinergic, anti a-adrenergic, anti-serotonergic effects. Less sedation. And are not useful for nausea or motion sickness.
28
H2 Receptor Antagonists are thought to be useful for...
reducing NSAID induced dyspepsia
29
Gastric ulcers are due to
NSAID use
30
Most peptic ulcers are due to...
H. Pylori infection
31
H2 receptor antagonists are associated with...
esophageal reflux few side effects infrequent GI irritation
32
cimetidine
potent inhibitor of P450 metabolism