Owenpharm Block 2 > Histamine > Flashcards

Histamine Flashcards

To rock the heck out of histamine! (67 cards)

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1
Q

From what essential amino acid does histamine come from?

A

L-histidine

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2
Q

What alteration can account for histamine intolerance in approximately 1% of the population?

A

Alteration in histamine degrading enzymes (DAO or HNMT)

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3
Q

What three roles does Histamine have?

A
  1. Mediator of immediate allergic inflammatory reactions
  2. Role in gastric acid secretion
  3. Neurotransmitter and neuromodulator
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4
Q

Where are the highest amounts of Histamine located? (3 locations)

A
  1. Lungs
  2. Skin
  3. GI tract
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5
Q

Where are “pools” of histamine stored in tissues & blood?

A

Tissues - Mast cells

Blood - Basophils

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6
Q

How are the “pools” of histamine managed in basophils?

A

Synthesized and stored in secretory granules in an inactive form

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7
Q

Histamine is bound to a proteoglycan intracellularly. What is this glycan in mast cells? in basophils?

A

Heparin-sulfate and ATP in mast cells

Chondroitin-sulfate in basophils

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8
Q

Is the turnover of Histamine in mast cells and basophils fast or slow?

A

Slow turnover

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9
Q

How is histamine handled differently in non-mast cells (gastric mucosa, epidermis, neurons)? (4 points)

A
  1. There are no granules
  2. Histamine is continuously synthesized and released
  3. There is a rapid turnover
  4. Histidine decarboxylase levels correlate with activity
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10
Q

What are the immediate effects of histamine release? (5 items)

A
  1. Burning/itching sensation
  2. Intense warmth
  3. Skin reddens
  4. BP decreases
  5. HR increases
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11
Q

What are the effects of histamine release within minutes (different than immediate)? (2 items)

A
  1. BP recovers

2. Hives appear

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12
Q

Describe the process of histamine release when there has been prior exposure to the antigen. (3 steps)

A

Binding of IgE to FceRI on mast cells
Antigen binding to IgE
Activation of mast cell with release of mediators

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13
Q

Describe the process of first exposure to an allergen in relation to histamine release.

A

Antigen activation of TH2 cells
Stimulation of IgE class switching in B cells
IgE secreted antibodies engage in future encounters

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14
Q

How is drug/peptide/venom release of histamine different that allergic release? (2 points)

A

It is not antigen-antibody mediated

Results in direct stimulation without prior exposure

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15
Q

What drugs cause direct stimulation of histamine release? (5 items)

A 
Succinylcholine
Morphine
Curare
Plasma expanders (dextran, PVP)
Vancomycin ("red-man syndrome")
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16
Q

What peptides can cause direct stimulation of histamine release? (3 items)

A

Bradykinin
Complement
Substance P (release during tissue injury)

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17
Q

What venom can cause direct stimulation of histamine release?

A

Wasp venom

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18
Q

What is the mechanism for direct stimulation of histamine release?

A

Increase in intracellular calcium

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19
Q

What is the clinical picture of Red-man syndrome? (2 items)

A

Rash to face, neck, upper torso

Hypotension

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20
Q

What is the name for the inhaled anti-inflammatory, anti-histamine agent used in asthma?

A

Cromolyn Sodium

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21
Q

What is the mechanism for Cromolyn Sodium? (2 points)

A

Stabilizes mast cell membrane to prevent release of histamine
Prevents mast cell degranulation

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22
Q

What is the primary route of admin for Cromolyn sodium?

What are the alternatives?

A

Inhalation

Oral, Nasal, Ophthalmic

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23
Q

What is the therapeutic utility of Cromolyn sodium? (3 points)

A

Chronic asthma control
Prophylaxis of bronchospasm (allergen- or exercise-induced)
Not a rescue medication!

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24
Q

What are the major uses for the Nasal, Ophthalmic, and Oral preparations of Cromolyn sodium?

A

Nasal - Allergic rhinitis
Ophthalmic - Conjunctivitis
Oral - Systemic mastocytosis

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25
What is the mechanism of action for Omalizumab? (2 points)
Decreases amount of antigen specific IgE | Binds tightly to free IgE to prevent FceRI binding
26
What is the route of administration for Omalizumab?
SQ
27
What adverse effects should one look for with Omalizumab? (2 points)
Injection site reaction | Anaphylaxis after first dose
28
What are the H1 histamine receptors primarily located? | What does activation of these affect?
Endothelial cells | Vasodilation
29
How does H1 & H2 receptor combined activation contribute to vascular dilation? (3 points)
H1 system coupled to increase in calcium H1 receptors activate NO synthase H2 receptors couples to increase in cAMP
30
What effect does H1 receptor activation have on large vessels?
vasoconstriction
31
What effect does activation of H1 and H2 have on BP overall?
decrease
32
Activation of H1 receptors have what effect on vascular permeability? Why?
Increased Located on post-capillary venules-endothelial cells Contraction of these cells causes exposure of basement membrane
33
What effect do H2 receptors have on cardiac myocytes? (2 points)
Increased contractility | Increased electrical conduction
34
What effects do H1 and H2 receptors have on bronchioles? (2 points)
H1 - contraction | H2 - relaxtion (minor)
35
Which histamine receptor causes intestinal smooth muscle contraction?
H1
36
Which histamine receptor causes gastric acid secretion?
H2
37
Which histamine receptor causes pain & itching in peripheral nerve endings?
H1
38
Which H receptor is responsible for increased arousal/wakefulness?
H1
39
What are the 4 first generation H1 receptor blockers for this course?
Diphenhydramine Dimenhydrinate Chlorpheniramine Promethazine
40
Which first generation H1 blocker also blocks dopamine receptors?
Promethazine
41
What are the 4 second generation H1 blockers for this course?
Fexofenadine Loratadine Cetirizine Desloratidine
42
What is the difference between first and second generation H1 receptor blockers?(2 points)
Second generation have little to no CNS effects | First generation also have mild/moderate muscarinic antagonism in CNS
43
What type of activity are H1 receptor blockers classified as having?
Inverse agonism
44
What are the major therapeutic effects of H1 antagonists?
Inhibition of vascular permeability Suppressed itching No effect on blood pressure No effect on bronchoconstriction
45
What effect do 1st generation H1 blockers have on CNS? (2 points) Is it different in children?
Sedation and Anti-cholinergic reduction in motion sickness Yes, can cause stimulation in children
46
Can anti-cholinergic effects be seen with H1 blockers? What kinds? Which generation?
Yes Dry mucus membranes, Urinary retention, "anti-cholinergic syndrome" 1st generation only.
47
What are the oral pharmacokinetics of H1 blockers? (2 points)
Rapid absorption | Peak conc. 1-2 hours
48
How are 2nd generation H1 blockers metabolized?
Liver P450 (CYP3A4/CYP2D6)
49
What is the metabolite of Terfenadine?
Fexofenadine
50
What is the metabolite of Loratadine?
Desloratadine
51
Hydroxyzine is metabolized to what active agent?
Cetirizine
52
How does a 1st generation H1 blocker cause sedation?
Central H1 effect and central anti-cholinergic effect
53
Which 2nd generation H1 blocker has the most sedative effect?
Cetirizine
54
Have there been any adverse effects seen of loratadine on QT interval?
No
55
Which H1 blockers exhibit a noticeable anti-cholinergic effect useful for motion sickness?
dimenhydrinate (dramamine) promethazine (phenergan) diphenhydramine (benadryl)
56
Off-label uses and the used (4 points)
Sleeping aid - Diphenhydramine Vestibular disturbance - Dimenhydrinate Nausea/Vomiting - Promethazine Early stage Parkinson's - Diphenhydramine
57
What are the indications for H2 receptor antagonists? (4 points)
Relief of symptoms peptic ulcer disease Gastroesophageal reflux disease Peptic ulcer secondary to H. pylori Gastric injury from NSAIDS
58
What is the mechanism of action for H2 receptor antagonists?
H2 receptor stimulation on parietal cells increases adenylyl cyclase, cAMP, and PKA --> this increases acid production. H2 blockers stop this activity.
59
Is H2 stimulation the terminal step in acid production?
No, Gastrin and ACH also have direct effect on parietal cells. Proton pump is terminal step.
60
What type of inhibitor are H2 antagonists?
Reversible competitive inhibitor (can act as inverse agonist)
61
What is the importance of the inverse agonism of H2 antagonists?
Inhibition of fasting acid secretion and inhibition of nocturnal gastric acid secretion is a big determinant in the healing of ulcers.
62
What common side effects are seen with H2 blockers?
Diarrhea, headache, drowsiness
63
What are less common effects seen mostly with IV administration in elderly patients?
confusion delirium slurred speech
64
What is the significance of Cimetidine that is not present with other H2 blockers?
Inhibition of P450 metabolism
65
What are the three H2 blockers for this course?
Cimetidine Famotidine Ranitidine
66
Long term use of high doses of Cimetidine can lead to what undesirable effects in men?
Decreased testosterone binding | Gynecomastia due to inhibition of estradiol hydroxylation
67
What is the order of potency of H2 blockers?
Famotidine (Pepcid) > Ranitidine (Zantac) > Cimetidine (Tagamet)
Owenpharm Block 2
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