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IHO Week 6 > Regal- Histamines and Anti-Histamines > Flashcards

Regal- Histamines and Anti-Histamines Flashcards

1
Q

Where is histamine synthesized?

A

nearly every tissue w/ highest concentration in the lungs and stomach

in mast cells or basophils
(any cells that contain L-his decarboxylase)

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2
Q

What does L-histadine decarboxylase do?

A

Converts histadine to histamine

Found in mast cells and basophils

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3
Q

What are the two pools of histamine?

A

Mast cell histmaine (mast cells and basophils)

Non-mast cell histamine (CNS nerve endings)

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4
Q

How is histamine degraded?

A 
Inactivated by metabolic enzymes 
N-methyltransferase
diamine oxidase
MOA-B
ribose
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5
Q

Where are the enzymes that degrade histamine located?

A

Widely distributed (small intestine mucosa, skin, kidney, liver thymus, WBC)

Intestinal bacteria convert it to N-actylhistamine

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6
Q

What are the three ways that histamine contributes to inflammation?

A
  1. vasodilation–> redness/heat
  2. increased vascular permeability–> swelling
  3. bronchoconstriction
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7
Q

What happens to orally administered histamine?

A

Absorbed and inactivated by enzymes of intestinal wall/liver

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8
Q

What happens to intracutaneously administered histamine?

A

Triple response

vasodilation–>Localized redness (s/m)

nerves dilating neighboring arterioles–> diffuse redness (slower)

Increased capillary permeability–> localized edema

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9
Q

What are nasal sxs associated w/ intranasal histamine?

A

Intense itching
sneezing
hypersecretion
nasal blockage

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10
Q

Intravenous administration of histamine leads to….

A 
vasodilation
decreased bp
tachycardia
bronchoconstriction
face flushing
HA
wheal and flare
stimulation of mucous secretion
stimulation of gastric secretion
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11
Q

What type of agonists are histamines?

A

Inverse agonists–reduce receptor activity below basal levels observed in absence of ligand (looks like a competitive antagonist)

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12
Q

What leads to the endogenous release of histamine?

A

Antigen interaction w/ IgE Ab on mast cells and basophils

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13
Q

Activation of H1 leads to:

A

rapid and short lived VASODILATION

bronchoconstriction
contraction of GI smooth muscle
increased capillary permeability (wheal)
pruritits and pain
release of catecholamines from adrenal medulla
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14
Q

Activation of H2 leads to:

A

Gastric acid secretion

SLOWER and SUSTAINED VASODILATON

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15
Q

Activation of H3 leads to:

A

Present on histaminergic nerve terminals

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16
Q

Activation of H4 leads to:

A

Present on immune cells

17
Q

What is the triple response caused by histamine and what receptors does it effect?

A

vasodilation-H1, H2
flare-H1 (some 2)
wheal- H1, some 2
pain and itching- H1

18
Q

What triggered histamine receptors lead to cardiac effects?

A

H1 and H2

Increased HR, force, arrythmias
Decreased AV conduction

19
Q

What are the two first generation antihistamines?

A

Diphenhydramine- Benadryl

Chlorampheniramine

20
Q

What is the MOA of first generations antihistamines?

A 
Block:
H1
muscarinic
alpha adrenergic 
5-HT receptors (cholinergic properties)
21
Q

Where are antihistamines distributed?

A

A: oral

D: widely includes CNS

22
Q

How are antihistamines eliminated?

A

A: liver inactives enzymes

E: renal

23
Q

What are the major toxicities associated w/ antihistamines?

A

Sedation
Drying of secretions

GI disturbances

24
Q

What receptor does Diphenhydramine act on?

A

H1 receptor antagonist

25
Q

What is a antihistamine toxicity that is minized by using diphenhydramine?

A

Lowers incidence of GI SE

26
Q

What is a unique property of diphenhydramine?

A

It’s good if you want a sedative effect (children)

27
Q

When is chlorepheniramine commonly used?

A

day time

28
Q

What are the second generation antihistamines?

A

Cetirizine
Fexofenadine
Loratadine

29
Q

What is the MOA of SG antihistamines?

A

Block H1 recetpors

MINIMAL anticholinergic propgerites

30
Q

How are SG antihistamines distributed?

A

D: does NOT cross BBB->

NO sedation or drying secretions

31
Q

What are toxicities associated w/ SG antihistamines?

A

some are cardiotoxic w/ overdose

32
Q

What of the SG antihistamines are cardiotoxic

A

NOT cetirizine, fexofenadine or loratadine!

IHO Week 6 (14 decks)

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