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HEENT > Histamine 1st generation > Flashcards

Histamine 1st generation Flashcards

1
Q

net effect of histamine in the CNS

A

increased wakefulness, alertness and reaction time

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2
Q

histamine antagonist in the CNS

A

histamine that distributes to the CNS leads to drowsiness and functional impairment

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3
Q

first generation vs second generation histamine and the CNS

A

first generation- extensive distribution to the CNS

second generation-much less distribution to the CNS

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4
Q

histamine vascular effects

A

histamine is a direct vasodilator
can lead to edema due to increased vascular permeability
can also manifest urticaria to certain patients

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5
Q

histamine and cardiac effects

A

minimal but H1- slows AV node conduction in large amounts can lead to dysrhythmias
H2 increase heart rate and cardiac output

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6
Q

histamine and anaphylaxis

A

histamine contributes to large blood pressure falls-called histamine shock

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7
Q

steps of histamine shock

A

1) small blood vessels dilate
2) large amount of blood trapped
3) plasma leaks into circulation
4) blood volume diminished
5) reduction in venous return
6) reduced cardiac output and reduced tissue perfusion

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8
Q

anithistamines and anaphylaxis

A

considered a useful but optional adjunct and not a life saving therapy
even with urticaria these are used for symptom relief

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9
Q

histamine and respiratory

A

histamine relseased from mast cells act on H1R

  • smooth musk constriction
  • bronchospasm
  • mucosal edema/secretion
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10
Q

histamine and HEENT

A

promotes many symptoms of allergic conjunctivitis, allergic rhinitis

  • increased nasal mucus production
  • increased neutrophil and eosinophil chemotaxis
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11
Q

histamine and GI

A

in the GI histamine stimulation of the H2 receptors increases secretion of gastric acids from parietal cells
- in large amounts histamine may stimulate smooth msk contractions and cause diarrhea

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12
Q

1st generation H1R antagonists

A

diphenhydramine, dimenhydrinate, meclizine, doxylamine, chlorpheniramine.

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13
Q

2nd generationH1R antagonists

A

loratadine, cetirizine, fexofenadine

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14
Q

Important 1st gen H1RAs with additional unique pharmacology or roles

A

cyproheptadine, hydroxyzine, doxepin, promethazine.

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15
Q

therapeutic uses of H1R antagonists

A

allergic rhinitis- can manage symptoms but much more effective at preventing taken before exposure

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16
Q

MOA of H1R antagonists

A

H1R are not actually antagonists they are inverse agonists
because of their ability to down-regulate the H1 receptor activity
-they shift the equilibrium from an active form of the H1 receptor to an inactive form

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17
Q

ADVERSE effects and risks of H1R antagonists 1st generation

A
  • more lipophilic so tend to cross the blood brain barrier
  • sedating (but can be activating in kids)
  • functional impairment w or w/o drowsiness
  • weight gain
  • hypersensitive reactions
  • prolonged QT interval and ventricular arrhythmias
  • some are highly anticholinergic (dry mouth and eyes, urinary hesitancy, confusion/falls, glaucoma increase IOP)
18
Q

usefulness of H1R antagonists

A
  • highly effective when applied locally for a single symptoms
  • rapid onset but best results when taken continuously
19
Q

ADVERSE effects and risks of H1R antagonists 2nd generation

A 
relatively non-sedating at appropriate doses
less lipophilic (less BBB permeation)
-generally better tolerated and longer duration of action 
-some are anticholinergic but more peripherally (bladder/vision)
20
Q

first generation to use during pregnnacy category A

A

doxylamine - Rx is usually combined with B6 for nausea and vomiting but can be taking by itself and is OTC-nyquil

21
Q

antihistamines with anit-muscarinic effects list

A

cyproheptadine>promethazine>desloratdine>diphenhydramine>loratadine>chlorpheniramine
* do not give to elderly

22
Q

antihistamines with zero anti-muscarinic effects list

A

fexofenadine and certirizine

23
Q

1st generation antihistamines add more CNS effects and antimuscarinic effects

A

Disorientation, reduced cognition, fall risk…
Risky in older adults, comorbid diseases (bladder, glaucoma, etc.)
Watch for “Tylenol PM” and related, in the older adult

24
Q

diphenhydramine

A

aka benadryl
1st genration H1RA with strong anti-muscarinic properties
-is metabolized by the liver and an inhibitor of CYP2D6

25
Q

diphenhydramine dosing and 1/2 life

A

oral: 25-50 mg every 4-8 hrs, max dose 300 mg/day

but T1/2 life in elderly can be 9-18 hrs of groggy sedation, even after therapeutic effect has stopped

26
Q

indications for diphenhydramine

A 
allergic rhinitis
anaphylaxis (adjunct)
common cold
insomnia (short term)
motion sickness
parkinsonism
pruritus
27
Q

cough and diphenhydramine

A

dries up post nasal drip

but not an antitussive persay but can reduce rhinitis associated cough

28
Q

antihistamines used for motion sickness and vertigo

A

dimenhydinate

meclizine

29
Q

dimenhydrinate

A

highly sedating
most effective OCT for motion sickness
30 min onset
contraindicated for under 2 years

30
Q

meclizine

A 
bonine-motion sickness
antivert-rx only
-less sedating but less effective
usually for motion sickness and vertigo
1 hr onset
12 an older
31
Q

doxepin

A

a tricyclic antidepressant and 1st generation
-MOST SEDATING MOST POTENT
use only after other antihistamines used with no response

32
Q

insomnia and depression/anxiety

A

doxepin insomnia 3-6 mg HS

anxiety/depression 25-50 mg HS

33
Q

hydroxyzine

A

rx only
sedative hypnotic
considered the preferred antihistamine for acute anxiety

34
Q

hydroxyzine pamoate uses

A

anxiety
pruitus
off label seasonal allergic rhinitis

35
Q

hydroxyzine hydrochloride

A 
alcohol withdrawal
anxiety (associated with EtOH withdrawal)
nausea 
vomiting
pruritus
36
Q

hydroxyzine mmajor active metabolite

A

cetirizine second generation (zertac)
commonly added to opiods for pain for nausea
also adds a dose sparing analgestic effect for opiods
*but is high CNS depression

37
Q

promethazine

A 
phenergan
for nausea and vomiting
contraindications
under 2
under 12
arterial and subcutaneous administration
cautions: hypersensitivtiy, treatment of lower respiratory tract, temperature dysregulation**, h/o neuroleptic malignant syndrome, cardiac conduction issures
38
Q

fever and promethazine

A

discontinue&** and monitor

39
Q

cyproheptadine

A

broad spectrum allergic condition

-blocks histamine and serotonin so long term use associated with depression

40
Q

Chlorpheniramine and brompheniramine

A

OTC antihistamine alone (Chlortrimeton®) and in combination (bromphenirmaine with pseudoephedrine) in original “Children’s” Dimetapp® [now only 12 and older…]
Rx in combination with hydrocodone in Tussionex® extended release cough syrup. (C-II)

HEENT (6 decks)

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