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Pharmacyology 3 > Antihistamines > Flashcards

Antihistamines Flashcards

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1
Q

Antihistamines

A

Histamine H1 receptor antagonists

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2
Q

1st gen antihistamines

A 
Chlorpheniramine
Diphenhydramine
Meclizine
Promethazine
Doxylamine
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3
Q

2nd gen antihistamines

A

Cetirizine

Fexofenadine

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4
Q

When is histamine released?

A

Allergic/inflammatory reactions

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5
Q

Functional histamine antagonists

A

Epinephrine

Cromolyn sodium

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6
Q

Cells that release histamine

A

Mast cells
Basophils
Enterochromaffine like cells (G cells)
Histaminergic neurons

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7
Q

Histamine is what type of hormone?

A

Autocoid (local)

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8
Q

Mast cells

A
  • For pathogen defense
  • in most tissue, near blood vessels
  • enriched at body interfaces (ears, eyes, nose, throat, gut)
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9
Q

Histamine release triggers

A
  • immunologic
  • chemical
  • tissue damage
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10
Q

Enterochromaffin-like cells

A
  • ## release histamine that act on H2 receptors on parietal cells
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11
Q

Which histamine receptor is therapeutically most relevant?

A

H1

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12
Q

Which histamine receptors are involved in allergic reaction?

A

H1, also H2 and H3

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13
Q

Histamine actions in allergic reactions

A
  • VSM dilation
  • increased vascular permeability
  • peripheral sensory nerve excitation
  • nasal congestion
  • bronchial smooth muscle contraction
  • intestinal smooth muscle contraction
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14
Q

VSM dilation in allergic reaction

A

Flushing
Fall in systemic BP
Reflex tachycardia

Small reaction —> H1 stimulated
Large —> H2

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15
Q

Where is H1 receptor?

A

Endothelium (NO)

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16
Q

Where is H2 located?

A

Smooth muscle cells (cAMP)

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17
Q

VSM dilation can cause what?

A

Histamine shock in systemic anaphylaxis

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18
Q

H receptors are what type of receptors?

A

GPCR

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19
Q

Increased vascular permeability in allergic reaction

A

Endothelial cell retraction
Edema/wheal formation (plasma and protein leaking)

H1 recpetor

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20
Q

Peripheral sensory nerve excitation in allergic response

A

Pain and itching

H1 and H3 receptors

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21
Q

Triple response of allergic reaction

A
  • rapid reddening
  • swelling (edema)
  • flare
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22
Q

Rapid reddening in allergic reaction is due to what?

A

Dilation of small vessels

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23
Q

Swelling (edema) in allergic reaction is due to what?

A

Increased vascular permeability

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24
Q

Flare in allergic reaction is due to what?

A

Neural activated vasodilation

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25
Triple response is used for what?
Quantify allergic response of an individual
26
Nasal congestion is from what H receptor?
H1
27
Bronchial smooth muscle contraction in allergic reaction
H1 Bronchial hyperactivity to histamine in asthmatics Involves neural response
28
Other histamine receptor actions
- H2 on gastric parietel cells - H2 on cardiac muscle - CNS (wakefullness, analgesic) - H4 modulate cytokine production - anaphylactic shock
29
Anaphylactic shock
- bronchospasms - severe hypotension - angioedema - mucous membrane congestion - CNS: confusion, anxiety - N/V - palpitations
30
What should you give in anaphylactic shock?
Epinephrine | H1 blockers not effective
31
Physiological antagonist of histamine
- occurs when chemicals counterbalance each other by producing opposite effects on same physiological function - Epi
32
Epi and histamine reaction
A1: NE activation, vasoconstriction (increase BP0 B2: NE activation, bronchodilation
33
Histamine release inhibitor
Cromolyn sodium
34
Cromolyn sodium and histamine
- inhibit lung mast cell histamine release | - prophylactic use in asthma, hay fever
35
First gen antihistamine overview
- enter CNS - sedation - anti-cholinergic effects - GI problems
36
2nd gen antihistamine overview
- mostly do not enter CNS - less sedating - less muscarinic action - more metabolized by CYP3A4 —> drug interactions
37
1st generation antihistamine metabolism
CYP450 most 2D6 - don’t have to worry about interfering with other drugs
38
Antihistamine excreteion
Urine | Feces (fexofenadine)
39
Antihistamine pharmacodynamics
- inhibit vasodilation and bronchial contraction - inhibit increased capillary permeability and edema/wheal formation (does not reverse) - anti allergic, anti inflammatory
40
Antihistamine use general information
- best to take before needed - symptom relief may be incomplete - tolerance usually does not develop - less effective with chronic/high antigen exposure
41
T/f tolerance usually develops in antihistamines
False | Usually does not
42
Antihistamine PK
Most 4-6 hours | 2nd gen are 12-24 hour
43
Antihistamine uses
- Seasonal allergic rhinitis and conjunctivitis (hay fever) - hives - anaphylaxis - atopic dermatitis (eczema) - CNS and vestibular disorders
44
For seasonal allergic rhinitis what are antihistamines combined with?
Pseudoephedrine | Phenylephrine
45
Antihistamines and anaphylaxis
- NOT to replace epinephrine | - only to reduce flushing, itching, urticaria, rhinorrhea
46
Antihistamines for motion sickness
- diphenhydramine - promethazine - meclizine
47
Antihistamines for antiemetic
Promethazine | Doxylamine
48
Antihistamines for insomnia
Diphenhydramine | Promethazine
49
Sedation from antihistamines can be enhanced by what?
EtOH and CNS depressants
50
CNS adverse effects of antihistamines
- sedation - dizziness, HA - stimulation in children
51
T/F there are fewer adverse effects with 2nd gen antihistamines
True
52
GI adverse effects of antihistamines
- due to muscarinic, adrenergic, serotonin receptor block - constipation/diarrhea - loss of appetite - N/V/ epigastric distress
53
Anti-muscarinic effects of antihistamines
- dry mouth and sinuses | - urinary retention
54
Antihistamines CI
Narrow angle glaucoma | Dysuria
55
Allergic reactions from antihistamines
- dermatitis - drug fever - some photosensitization
56
Antihistamine overdose
Tachycardia Dry mouth Dilated pupils Hallucinations
57
T/F caution in pregnancy with antihistamines
True
58
T/F generally avoid 2nd gen antihistamines in children and elderly
False | 1st gen
59
Diphenhydramine uses
- allergic rhinitis - dermatologic pain and itching - insomnia - motion sickness
60
Adverse effects of diphenhydramine
- sedation - excitation in children - reduce lactation - enter breast milk - avoid in narrow angle glaucoma
61
Chlorpheniramine use
- allergic rhinitis - dermatologic pain and itching - OTC cold (>2-4 yo)
62
Adverse effects of chlorpheniramine
- sedation, but less than benadryl - less muscarinic effects - still glaucoma concern
63
Promethazine use
- antiemetic | - sedative
64
Adverse effects of promethazine
- similar to other 1st gen | - photosensitivity
65
BBW promethazine
- respiratory depression (<2yo) | - severe tissue injury with injection
66
Meclizine use
- vertigo | - prevent motion sickness
67
Adverse effects of meclizine
Sedation (less than other 1st gens)
68
Diclegis
Doxylamine + pyridoxine (vitamin B6)
69
Diclegis use
Morning sickness | Sedative
70
T/F 2nd gen antihistamines have increased 1st pass effect
True
71
Cetirizine use
- allergic rhinitis | - dermatologic pain and itch
72
Adverse effects of cetirizine
- very well tolerated - some sedation - weak anti-muscarinic effects - metabolized by CYP3A4
73
Fexofenadine use
- allergic rhinitis (oral only) | - dermatologic pain and itching (better prophylactically)
74
Adverse effects of fexofenadine
- usually well tolerated - not sedating - dysmenorrhea - enters breast milk
75
Which antihistamine should you NOT take with fruit juice?
Fexofenadine (reduces absorptioN) | - OATP transport for absorption, not a CYP3A4
76
Decongestant general use
- relief from nasal congestion and pressure

Pharmacyology 3 (12 decks)

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