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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
Q

If patient is taking antihistamine, does it block release of histamine?

A

No, H1R is a receptor and triggers a cascade

Only blocking downstream effects of histamine

26
Q

Diphenhydramine…mech and administration

A

Inverse agonist of H1 receptor and not inhibitor of histamine release

Administer prior to histamine release

Orally and topically…4-6 hours

27
Q

Side effects of benadryl

A

Crosses BBB so sedation and antimuscarinic properties (dry mouth, tachycardia, blurred vision, constipation)
Has off target effects
Not many GI effects

28
Q

Promethazine mech, when it is used, onset of action and other effects

A

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
Q

Doxepin use, peak, side effects

A

H1 antagonist
Used as antidepressant
6-24 hours
Drowsiness and anticholinergic effects

30
Q

Terfenadine

A

2nd generation
Caused cardiac arryhtmia
Prodrug metabolized by CYP3A4

31
Q

Fexofenadine duration of action, onset, mechanism, and advantage

A

12 hour duration
1 hour onset
Active metabolite of terfenadine but does not have side effects
Minimal sedative or antimuscarinic activity

32
Q

Ceterizine mech, side effects, duration, T1/2

A

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
Q

Loratadine metabolism, onset of action, duration, and peak

A

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
Q

Desloratidine

A

Clarinex - active metabolie of loratadine

35
Q

Excretio of 1st gen vs 2nd

A

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
Q

In general, drug interactions and side effects of antihistamines

A

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
Q

Olopatadine

A

Potent H1 antihistamine but also stablilizes mast cells and has anti-inflam effects

Used for allergies

38
Q

Allergic dermatose use of antihistamines

A

Use with corticosteroid

39
Q

Allegra topical

A

Diphenhydramine, not fexofenadine

40
Q

Anti-emetic effects of H1s

A

Prometh, doxylamine, diphenhydramine
Vomiting center rich in H1 receptors
Also used to treat parkinsons

41
Q

Sleep aids antihistamines

A

1st generation

Diphenhydramine is in Unisom, Nytol. Sleep-Eez, and Sominex

42
Q

Antihistamines and corticosteroids in place of epinephrine?

A

No, use those after patient stabilizes

43
Q

Asthma and antihistamines

A

1st gen not useful
2nd gen might be
Also not useful in treating cold and flu, but may benefit runny nose

44
Q

One histamine that IS good for asthma

A

VUF-6002 H4 receptor inhibitor

45
Q

Nyquil, theraflu, and traiaminic contain

A

Nyquil - doxylamine
Theraflu - diphenhydramine
Traminic - chlorpheniramine

Basically just makes you sleepy

46
Q

Would fexofenadine be useful in ulcer tx

A

No, because those are H2 receptors

47
Q

Why would drug like benadryl cause constipation?

A

Inhibits smooht muscle contraction by inhibiting H1 receptors

Foundations 6 (17 decks)

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