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Pulmonary Week 3 > Anti-Histamines > Flashcards

Anti-Histamines Flashcards

1
Q

What are some common 1st generation anti-histamines?

A
  • Diphenhydramine (Bendryl)
  • Dimenhydrinate (Dramamine)

all short acting (4-6 hrs)

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2
Q

What are some 2nd generation anti-histamines?

A
  • Fexofenadine (Allegra)
  • Loratadine (Claritin)
  • Cetirizine (Zyrtec)
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3
Q

How is histmaine synthesized?

A

via L-histadine by giving off water

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4
Q

What cells make histamine?

A
  • mast cells (less likely to circulate)
  • basophils
  • CNS neurons (its a neurotransmitter)
  • epidermal cells and intestinal mucosa
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5
Q

Functions of histamine?

A
  • stimulate production of hydrochloric acid in stomach
  • vasodilation in allergies/etc.
  • neurotransmitter: regulates sleep, brain arousal, memory
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6
Q

Histamine is mediated by 4 receptors and is only active when bound to an appropriate receptor

A

Histamine is mediated by 4 receptors and is only active when bound to an appropriate receptor

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7
Q

What are the effects of H1 binding?

A

-increased vascular permeability
-enhancement of histamine and arachidonic acid
derivatives release,
-NO formation,
-increased wakefulness

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8
Q

Clinical effects of H1 binding?

A

Sneezing, itching, rhinorrhea
and perhaps some degree of nasal congestion via increase vascular permeability with leakage of fluid into the tissues and vasodilation

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9
Q

What are the effects of H2 binding?

A

stimulate mucous glands
in airways, increases vascular permeability;

stimulate release of gastric acid (most important)

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10
Q

Clinical effects of H2 binding?

A

Potentially increase nasal
airway swelling, producing
nasal congestion and perhaps increased rhinorrhea

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11
Q

What are the effects of H3 binding?

A

stimulate nasal sub-mucosal gland secretion

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12
Q

Clinical effects of H3 binding?

A

can produce a runny nose

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13
Q

What are the effects of H4 binding?

A

Chemotaxis and chemokinesis of mast cells and eosinophils, enhancement of the activity of other chemoattractants (e.g. chemokines) on eosinophils, upregulation of adhesion molecules

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14
Q

Clinical effects of H4 binding?

A

Could enhance the

inflammatory response to nasal allergen exposure

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15
Q

What causes histamine release?

A

IgE binding and crosslinking to mast cells (takes several days to restore the reserves of histamine)

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16
Q

How does H1 binding affect arteries? arterioles?
capillaries?
venules? veins?

A

arteries- smooth muscle constriction and endothelium dilation

arterioles- rapid onset, short term dilation

capillaries-none

venules- rapid onset, short term dilation, capillary permeability

veins- smooth muscle constriction and endothelium dilation

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17
Q

How does H2 binding affect arteries? arterioles?
capillaries?
venules? veins?

A

H2 all dilation (slower onset, but more persistent)

capillaries still not effect (same as H1)

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18
Q

What is the net effect of histamine in the vasculature?

A

vasodilation via H1 receptors everywhere (H2 is minor everywhere outside the stomach)

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19
Q

What does H1 binding in the lungs cause?

A

broncho-constriction

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20
Q

Roles of H1 antagonists?

A
  • attenuation of allergy and hay fever symptoms

- treatment of symptoms of insect bites, stings, and contact flora poisoning

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21
Q

What additional effect do 1st gen H1 antihistamines have?

A

attenuation of motion sickness and vertigo

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22
Q

Which generation of anti-histamines have anti-cholinergic effects?

A

1st generation only

23
Q

Which generation of anti-histamines has a shorter duration of action?

A

1st-multiple doses required

24
Q

Why do the 1st generation anti-histamines cause sedation?

A

H1 receptors in the hypothalamus binding to histamine promotes alertness (these can pass the BBB because they are mostly uncharged)

25
Q

T or F. 1st generation anti-histamines have anti-asthmatic effects

A

FALSE. They increase the viscosity of bronchial secretions and decrease cilia motility via anti-cholinergic effect (do not take if asthmatics)

2nd gen are safer

26
Q

T or F. 1st generation anti-histamines can prevent the release of histamine endogenously

A

F.

27
Q

AEs of 1st generations?

A

the main AEs stem from the fact that H1 receptor antagonists can bind to other types of receptors

28
Q

What other receptors can 1st gen H1 receptor antagonists bind to?

A
  • muscarinic receptors
  • a-adrenergic receptors
  • serotonergic receptors
  • Ikr and other cardiac channels
29
Q

What are the (other) effects of H1 receptor binding of 1st gen H1 receptor antagonists?

A
  • sedation

- increased appetite

30
Q

What are the effects of muscarinic receptor binding of 1st gen H1 receptor antagonists?

A
  • xerostomia (dryness)
  • urinary retention
  • sinusoidal tachycardia
  • can bind CN XIII to block transmission to vomit center in the brain

beneficial in treatment of vertigo and motion sickness

31
Q

What are the effects of a-adrenergic receptor binding of 1st gen H1 receptor antagonists?

A
  • hypotension,
  • dizziness, and
  • reflex tachycardia
32
Q

What are the effects of serotonergic receptor binding of 1st gen H1 receptor antagonists?

A

-increased appetite

33
Q

What are the effects of Ikr and other cardiac channels receptor binding of 1st gen H1 receptor antagonists?

A
  • QT prolongation

- ventricular arrhythmia

34
Q

T or F. 2nd generation anti-histamines are far more specific for H1 receptors

A

T.

35
Q

Properties of 2nd generation H1 antagonists?

A
  • good H1 blockade and anti-asthmatic (safe) effect
  • no sedation, GI effect, anticholinergic effect
  • doesn’t inhibit histamine release

long acting

36
Q

T or F. 2nd generation H1 blockers are good for the treatment of asthma

A

No, they are just safe if you need to take one and are asthmatic

37
Q

What is the role of 3rd generation anti-histamines?

A

increase specificity and binding to H1 receptor and block histamine release

38
Q

What is Desloratadine (Clarinex®)?

A

Exhibits 14- to 17-fold greater binding to H1 receptors than
loratadine.

• 15- to 50-fold lower affinity for muscarinic receptors
(M1,M2,M4,M5) compared with H1-receptors.

• Has a relatively long elimination half-life (27 hours).

39
Q

What is Olopatadine (Patanol®)? Advantages?

A

• Its selectivity for the H1 receptor is greater than that of other ocular
antihistamines.

• Inhibits the release of histamine from mast cells.

40
Q

Other advantages of Olopatadine?

A

• Olopatadine may block the activities of some additional mediators of
ophthalmic inflammation by inhibiting the release of tryptase and
prostaglandin D2 from inflammatory cells.

• The drug prevents or reduces ocular inflammation reactions induced
by a variety of common allergens.

41
Q

How does Levocabastine (Livostin®) work?

A

• Rapid-acting agent for as needed-use against nasal and ocular effects of rhinitis.

• Piperidine derivative: 1250 times more potent than
chlorpheniramine. 40,000 times the effective dose exhibits no other pharmacological effects.

42
Q

What does Azelastine (Astelin®, Astepro ®) do?

A

Inhibits both histamine and
leukotriene activity.

  • Blocks calcium mobilization and the 5-lipoxygenase pathway.
  • Inhibits PAF through receptor antagonism.
43
Q

What is Emedastine (Emadine®) approved to treat?

A

allergic conjunctivitis.

44
Q

How does Emedastine work?

A

Anti-allergic potency is comparable to other 2nd generation H1-antagonists.

  • Also inhibits histamine and LTC4 release from leukocytes in asthmatic patients.
  • Anti-asthmatic potency is comparable to ketotifen
45
Q

What is Mizolastine (Mistamine®) approved to treat?

A

allergic rhinitis and chronic idiopathic

urticaria.

46
Q

How does Mizolastine work?

A
  • Antagonizes PAF- and LTD4-induced bronchoconstriction.
  • Effective in relieving nasal and ocular symptoms of seasonal allergic rhinitis.
  • Relatively non-sedative at antiallergic doses with no significant difference in efficacy over other non-sedating agents.
47
Q

What is Ebastine?

A

Hybrid of 1st generation (diphenylpyraline) and 2nd generation (terfenadine) H1-
antagonists.

48
Q

Effects of Ebastine?

A

Exhibits antileukotriene and antibradykinin activities 5-fold lower than anti-histaminic activity.

• Anti-histaminic potency is greater than that of loratadine with similar adverse effects

49
Q

Which generations of anti-histamines would be good for allergic rhinitis?

A

both

50
Q

Which generations of anti-histamines would be good for urticaria?

A

both

51
Q

Which generations of anti-histamines would be good for atopic dermatitis?

A

both

52
Q

Which generations of anti-histamines would be good for asthma?

A

neither, but 2nd is safe

53
Q

Which generations of anti-histamines would be good for itching dermatosis?

A

both, 1st slightly better

54
Q

Which generations of anti-histamines would be good for motion sickness, insomnia, appetite stimulation, and as an antiemetic?

A

1st only

Pulmonary Week 3 (18 decks)

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