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Foundations 6 > Antihistamines > Flashcards

Antihistamines Flashcards

1
Q

Histamines found at highest levels in

A

Lung, skin, intestine

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2
Q

Histamine stored and released in

A 
Mast cells (organs)
Basophils (blood)
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3
Q

Histamine synthesis

A

Histidine converted to histamine via histidine decarboxylase

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4
Q

Could you make a protein out of histamine?

A

No, no CO2 group

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5
Q

When does histamine release occur?

A

Type 1 allergic rxn
Tissue injury
Drugs or foreign compounds

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6
Q

Allergic reaction

A

IgE generated, docks in mast cells/basophils…histamine synthesized and stored in acidic secretory granules…degranulation response

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7
Q

Histamine medaites

A

Production of prostaglandins, leukotriens, and chemotactic agents

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8
Q

By blocking histamine, are all effects of mast cell degranulaton blocked?

A

No, many immune mediators involved

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9
Q

H1 receptor tissue, mech and effects

A

Nonvascular smooth muscle, vascular smooht muslce, brain

Increase DAG and IP3

Increase vascular permeability, increase vasodilation, constrict non-vascular smooht muscle

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10
Q

H2 receptor tissue, mech and effects

A

Gastric mucosa, cardiac muscle, mast cells in brain, and vascular smooht muscle

Increase cAMP

Increased gastric acid, increase casodilation, cardiac stimulation

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11
Q

H3 receptor tissue, mech, and effects

A

CNS
Increase cAMP
Decrease histamine release and increase NT release

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12
Q

H4 receptor tissue, mech, and effects

A

Immune cells
Increase cAMP
Mediate immune cell recruitment

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13
Q

Cardiovascular effects of histamines

A

Decrease in peripheral resistance due to hypotension
Rapid effects from H1R and prolonged from H2R
Rapidly metabolized so responses transeint
Can also increase pulse rate and contractility via H2 receptor

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14
Q

Respiratory effects of histamines

A

Bronchoconstriction via H1

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15
Q

GI effects of histamines

A

Induces smooth muscle contraction via H1 receptor causing diarrhea and cramps
Increase gastric acid secretion via the H2 receptor

Binds ECL cells to achieve this function

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16
Q

CNS effects of histamine

A

Increases wakefullness and inhibits appetite…decreases aggression

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17
Q

HIstidine decarboxylase inhibitors and brain

A

Increase feeding

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18
Q

H1R knockout mice

A

Increase feeding and decrease energy expenditure…histmaine may occur downstream of leptin

Also have aggression and locomotion probs

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19
Q

H1R antagonists show same effect as

A

H3R agonists…suggest converse roles in regulating sleep

20
Q

All drugs we are learning are

A

Inverse agonists of the H1 receptor

21
Q

Histamine effect on H1 receptor

A

Stabilizes in active state

22
Q

Antihistamine effect of receptor

A

Holds in inactive state

23
Q

First generation antihistamine metabolism

A

CYP450 in liver

24
Q

H1 antagonists tend to

A

Inhibit capillary permeability with little effect on bronchoconstriction and hypertension

25
If patient is taking antihistamine, does it block release of histamine?
No, H1R is a receptor and triggers a cascade | Only blocking downstream effects of histamine
26
Diphenhydramine...mech and administration
Inverse agonist of H1 receptor and not inhibitor of histamine release Administer prior to histamine release Orally and topically...4-6 hours
27
Side effects of benadryl
Crosses BBB so sedation and antimuscarinic properties (dry mouth, tachycardia, blurred vision, constipation) Has off target effects Not many GI effects
28
Promethazine mech, when it is used, onset of action and other effects
Phergan H1R inverse agonist with significant central anticholinergic effects (inhibits muscarinic acetylcholine receptor)...also sedative and antiemetic effects Used in combo with cold products in relief of motion sickness and vomiting 15-60 minute onset ...peak at 4-6 hours...sedative 2-8 hours
29
Doxepin use, peak, side effects
H1 antagonist Used as antidepressant 6-24 hours Drowsiness and anticholinergic effects
30
Terfenadine
2nd generation Caused cardiac arryhtmia Prodrug metabolized by CYP3A4
31
Fexofenadine duration of action, onset, mechanism, and advantage
12 hour duration 1 hour onset Active metabolite of terfenadine but does not have side effects Minimal sedative or antimuscarinic activity
32
Ceterizine mech, side effects, duration, T1/2
Second generation Poor penetration of BBB so sedation limited but drowsiness still side effect and dose related T1/2 = 8 hours Duration = 12-24 hours
33
Loratadine metabolism, onset of action, duration, and peak
By GI tract and converted to active via P450 enzyme (prodrug) Does not cross BBB and preferneitaly binds peripheral receptors Onset is 1-3 hours, peak at 8-12, duration greater than 24 hours
34
Desloratidine
Clarinex - active metabolie of loratadine
35
Excretio of 1st gen vs 2nd
1st generation metabolized by liver and excreted in urine Diphenhydramine and promethazine modified by CYP2D6 2nd generation not metabolized so fewer interactions (Loratidine is exception)
36
In general, drug interactions and side effects of antihistamines
Interactions between depressants like barbiturates Interaction with alcohol causing excessive sedation At high doses should not be give nto people operating car or machinery Some of anticholinergic effects can be more severe int he elderly
37
Olopatadine
Potent H1 antihistamine but also stablilizes mast cells and has anti-inflam effects Used for allergies
38
Allergic dermatose use of antihistamines
Use with corticosteroid
39
Allegra topical
Diphenhydramine, not fexofenadine
40
Anti-emetic effects of H1s
Prometh, doxylamine, diphenhydramine Vomiting center rich in H1 receptors Also used to treat parkinsons
41
Sleep aids antihistamines
1st generation | Diphenhydramine is in Unisom, Nytol. Sleep-Eez, and Sominex
42
Antihistamines and corticosteroids in place of epinephrine?
No, use those after patient stabilizes
43
Asthma and antihistamines
1st gen not useful 2nd gen might be Also not useful in treating cold and flu, but may benefit runny nose
44
One histamine that IS good for asthma
VUF-6002 H4 receptor inhibitor
45
Nyquil, theraflu, and traiaminic contain
Nyquil - doxylamine Theraflu - diphenhydramine Traminic - chlorpheniramine Basically just makes you sleepy
46
Would fexofenadine be useful in ulcer tx
No, because those are H2 receptors
47
Why would drug like benadryl cause constipation?
Inhibits smooht muscle contraction by inhibiting H1 receptors

Foundations 6 (17 decks)

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