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Anti-Histamine Flashcards

(50 cards)

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1
Q

What are various conditions that you can use anti-histamines for?

A
  1. Allergic rhinitis
  2. Eczema
  3. Urticaria (hives)
  4. Insomnia
  5. Motion sickness
  6. GERD/ Peptic ulcer disease
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2
Q

where is histamine generally found? and what do they do?

A
  1. Mast cells, basophils- defend against allergic reactions
  2. CNS- act as neurotransmitters
  3. Gut- regulates gastic acid production
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3
Q

Where are H1 receptors located?

A

Bronchial smooth muscle,

CNS,

Endothelium,

Cardiac muscle

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4
Q

What are the action of histamine binding to H1 receptor?

A
  1. Sleep-wake cycle (wakefulness)
  2. learning/ memory
  3. stimuate nerve endings (pain)
  4. bronchocontriction
  5. vasodilation of blood vessls
  6. contraction of smooth muscke
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5
Q

Where are the H2 receptors located?

A
  1. Parietal cells of the stomach
  2. Cardiac Tissue
  3. CNS
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6
Q

What is the action of histamine binding to H2 receptors?

A
  1. Gastic acid production
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7
Q

Where are H3 receptor located?

A
  1. CNS peripheral tissues
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8
Q

What is the action of histamine binding to H3 receptors?

A

Modulation of NE release

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9
Q

Where are the H4 receptors located?

A
  1. Basophils
  2. Bone marrow
  3. Small intestine
  4. Colon
  5. Spleen
  6. Thymus
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10
Q

What is the action of histamine binding to H4 receptors?

A

Faciliates mast cell chemtaxis

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11
Q

Overall effects of histamine release

A
  • Increased vasular permiabiligy- hypotension
  • Bronchocontriction
  • Increased bowel peristalsis- diarrhea
  • Cardiac effects
    • enhances influx of Ca into cardiac myocytes which increases contractility
    • Hypotenion secondary to vasodilation
    • Tachycardia
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12
Q

What happens when histamine in mast cells during allergic reaction?

A
  • B cell activation which turn into plasma cells that produce IgE.
  • IgE primes mast cells and when a person is exposed to allergens the mast cells degranulat and release histamines
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13
Q

Explain how cardiac patients are more susceptible to allgeric reactions?

A

Patients with cardiomyopathy, arrhythmoa or other structural heart disease

  • increase expression in mast cells
  • in allergic reaction- will release large quantities of mast cells
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14
Q

What is the role of histamine in immune modulation?

A

Vasodilation→ capilaries become more permeable → allows for WBC to move into site

  • Leads to facial flushing and edema
  • speration of endothelial cells → urticaria
  • Induces fluid secretion
    • gives rise to classic allergy symptoms- Runny nose, water eys, etc.
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15
Q

Explain how histamine works in the parietal cells in the GI tract?

A
  • Histamine bins to H2 receptors
    • increase cAMP
  • Gastin and Ach bind to their receptors (bind first)
    • increase Ca+
  • Gastrin binding casues release of histamine in the GI tract
    • histamine then binds to its receptor
  • Increase in cAMP and increase in Ca
    • acttivation of proton pump
      • H+ is pumped out into the lumen of th stomach
        • production of HCL
      • K+ is pumped into the parietal cell
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16
Q

Histamine in CNS

A

Considered a eurotransmitter (H1, H3 in the brain; some H2)

Modulators

  • Ach release → learning& cognition
  • Alertless → makes wake-cycle
  • Seratonin → mood
  • Food intake → supression of appetite
  • Emesis center → nausea/ vomitting
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17
Q

What do antihistamine do on H1/H2 receptors?

A

H1

  • Brochodilation
  • Constipation (decrease peristalsis)
  • Anti-itch, reduction of pain
  • Reduce the inflammation/ allergic respone

H2

  • Supression of gastric acid/ production
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18
Q

Epinephrine

A

Histamine Antagonist- works quickly

  • Smooth muscle relaxation
  • stimulates alpha and beta recptors

Vasodilation and increase BP

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19
Q

Cromolyn

A

Works over several week

Stabilizes mast cells to prevent degranulation

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20
Q

What do H1 blockers treat?

A

Treat allergies

insomnia

mottion sickness

Includes first and second generation

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21
Q

What are first generation antihistamines

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A

Treatment- allergic symptoms, motion sickness and insomnia

Poor receptor selectivity- anti-muscarinic, anti-alpha adrenergic, anti-seratonin

  • causes constipation, dry mouth, memory impairment, hypotension

Highly lipophilic

  • Cross BBB to interfere with histamine transmission- used to treat nausea and vomitting

NOT PREFERED IN ELDERS

22
Q

Doxylamine

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A

First generation H1 blockers

Anti-cholinergic effect +++ (Hot, dry fast, crazy)

Used for insomnia, allergies

Highly sedating, large doses can cause arrhythmias (QTC prolongation- block K+ receptors), Avoid in elderly

23
Q

Diphenhydramine

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A

First generation H1 blockers

Anti-cholinergic effect +++ (Hot, dry fast, crazy)

Used for insomnia, allergies

Highly sedating, large doses can cause arrhythmias(QTC prolongation- block K+ receptors), Avoid in elderly

24
Q

Cyclizine

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A

First generation H1 blockers

Anti-cholinergic effect + (Hot, dry fast, crazy)

Used for motion sickness, vertigo

mildly sedating

25
Meclizine
First generation H1 blockers Anti-cholinergic effect + **(Hot, dry fast, crazy)** Used for motion sickness, vertigo mildly sedating
26
Chlorpheniramine
First generation H1 blockers Anti-cholinergic effect ++ **(Hot, dry fast, crazy)** Used for allergies moderately sedating, possible prardoxical CNS stimulation **Often combined with cold products** **_Avoid in elderly_**
27
Brompheniramine
First generation H1 blockers Anti-cholinergic effect ++ **(Hot, dry fast, crazy)** Used for allergies moderately sedating, possible prardoxical CNS stimulation **Often combined with cold products** **Avoid in elderly**
28
Hydroxyzine HCl
First generation H1 blockers Anti-cholinergic effect + **(Hot, dry fast, crazy)** Used for allergies, urticaria Mid-moderate sedation
29
Hydroxyzine PAMoate
First generation H1 blockers Anti-cholinergic effect ++ **(Hot, dry fast, crazy)** Used for insomnia, anxiety- **cross BBB** Mid-moderate sedation
30
Promethazine
First generation H1 blockers Anti-cholinergic effect +++ **(Hot, dry fast, crazy)** Used for anti-emetic, highly sedating, alpha blockade→ hypotension, D2 blockade→ dystonic reactions, akathisia **Potent anti-muscarinic effects** **_Avoid in elderly_**
31
Cyproheptadine
First generation H1 blockers Anti-cholinergic effect + **(Hot, dry fast, crazy)** Weight gain due to 5-HT2 bloackade **used to treat seratonin syndrome and in cachexia**
32
DDI with first generation H1 blockers
Metabolized via 2D6 and 3A4 Avoid with * alcohol (synergestic sedative effects) * Other hypnotics and/ or benzos * TCA * Acetylcholinesterase inhibitors
33
Second generation H1 antihistamines
Used to treat allergic symptoms only highly **selective for H1 receptors** with no other receptors wffecrs **Limited penetration to BBB- minimally or non- sedating** Preferred in elderly Rapid onset Longer duration of action
34
Azelastine
Second generation H1 blocker Nasal spray **MOA- Mast cell stabilizer + H1 blocker** Nasal spray→ **less systemic side effects** Local irritation can occur- nasal irritation, nosebleeds, bitter taste/ smell **Avoid use if any preexisitng damage to the nasal pasage**
35
Olopatidine
Second generation H1 blocker Nasal spray **MOA- Mast cell stabilizer + H1 blocker** Nasal spray→**less systemic side effects** Local irritation can occur- nasal irritation, nosebleeds, bitter taste/ smell **Avoid use if any preexisitng damage to the nasal pasage**
36
Fexofenadine
Second generation H1 blocker Highest safety profile, NO CYP 450 metabolism, excreted in feces **NO RENAL DOSE ADJUSTMENT**
37
Cetirizine
Second generation H1 blocker MOst somnolence of second generation- gets into BBB Active metabolite of **hydroxyzine** (first generation H1 blocker)
38
Levocetirizine
Second generation H1 blocker Active metabolite of **cetirizine**
39
Loratidine
Second generation H1 blocker Metabolized via 3A4, 2D6→ **check 3A4 inhibitors**
40
Desloratidine
Second generation H1 blocker Least likely to cause somnolence Active metabolite of **loratadine**
41
Potencies of second generation
Potency: Desloratidine\> levocetirizine\> fexofenadine sits on receptor with higher affinity does not mean its more effective * if someone is one a lower potenty drug like fexofenadine and it doesn't work switch to a higher potency drug like levocetirizine or desloratidine
42
ADR of second generation antihistamine
Somnolence * at high doses * highest with cetirizine and levocetirizine Constipation Headache **No signifcant cardiac effect**
43
DDI with second generation H1 blocker * Fexofenadine * Loratidine * desloratidine * ceterizine * levocetirizine
* Fexofenadine * avoid grapefruit, orange and apple juice (compund that impairs absorption) * must seperate by at least 4 hours * Loratidine, desloratidine * metabolized via 3A4 and 2C6 * erythromycin, ketoconazole, clarithromycin, cimetidine and grapefruit juice * Avoid with alcohol and benzo * ceterizine, levocetirizine * PgP substrates→ DDI with grapefruit jucie and colchicine * Avoid other sedative drugs→ additive effect
44
H2 receptor antagonist
Reversibly decreases fasting and food stimulated acid secretion by inhibiting histamine on the histamine 2 receptor of the parietal cell Used for **episodic heartburn** **Good for on-demand, meal provoked symptoms** Onset- 30-45 min Duration- 4-10 hours all equally efficacious **OTC 1/2 the perscription dose** **Absorption may be delayed by administration of antacids but not by food** * **bioavailability of cimetidine and ranitidine reduced with simultaneous hgih dose antacids**
45
Rantidine
H2 receptor antagonist used for episodic heartburn
46
Cimetidine
H2 receptor antagonist used for episodic heartburn
47
Nizatidine
H2 receptor antagonist used for episodic heartburn
48
Famotidine
H2 receptor antagonist used for episodic heartburn
49
ADR associated with h2 blcokers
well tolerated ADR are mostly CNS related (H2 recptors in the CNS) Headache, dizziness, fatigue,confusion (incidence increased in elderly and renal impairment) **Dose related gynecomastia with cimetidine** **Tolerance reported with porlonged use (use PRN)**
50
H2 blockers DDI
Drugs depend on acid for proper absorption * ketoconazole, itraconazole, protease inhibitors (atazanivir), calcium carbonate, iron salts Cimetidinne inhibits CYP450 enzymes (3A4, 2D6, 1A2, 2C9) * substrates- cyclosprine, amiodarone, theophylline, phenytonin, antidepressants, warfarin

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