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Pharmacology > Histamines > Flashcards

Histamines Flashcards

1
Q

What is histamine?

A

endogenous biogenic amine which is synthesized, stored, and released from mast cells, basophils, and neurons

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2
Q

Histamine synthesis occurs from?

A

synthesis of histidine by l-histidine decarboxylase

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3
Q

How is histamine metabolized?

A

metabolized by hepatic P450 systems via 2 distinct pathways:

Methylation to N-methyl histamin and N-methyl imiadazole acetic acid (MAO) prior to urinary excretion

Oxidative deamination to imidazole acetic acid (DAO) and imidazole acetic acid ribodide prior to urinary excretion

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4
Q

Histamine recpetors are all members of what family?

A

G-protein coupled receptors

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5
Q

H1 receptors

A

in bronchial and intestinal smooth muscle, vascular endothelium, cardiac tissue, and CNS

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6
Q

H2 receptors

A

vascular smooth muscle, cardiac tissue, basophils, and parietal cells

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7
Q

H3 receptors

A

distributed throughout CNS

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8
Q

H4

A

within bone marrow and WBCs

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9
Q

Mild to moderate pathological effects of histamine include?

A

skin reactions (erythema, urticaria, itching), tachycardia, dysrhythmias, hypotension, mild resp distress

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10
Q

Anaphylactic pathological effects of histamine include?

A

hypotension, VF, cardiac arrest, bronchospasm, resp arrest

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11
Q

Histamine vascular effects

A

dilation of small blood vessels (H1 and H2) and increased permeability of post capillary venules

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12
Q

What is triple respone of Lewis in response to intradermal histamine injection?

A
  1. localized red spot
  2. flare develops more slowly extending beyond red spot
  3. wheal is disccemable 1-2 min at intial site
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13
Q

Histamine cardiac effects

A 
increased inotropy (H1 and H2)
increased chronotropy (H2)
decreased AV conduction (H1)
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14
Q

Histamine pulmonary effects

A

bronchoconstriction and increased mucous visccity (H1)
slight bronchodilation and increased mucous secretion (H2)
cough (H1)

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15
Q

Histamine GI effects (TQ)

A

increased acid production (H2)

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16
Q

Histamine neuronal effects

A 
cutaneous itching (H1 and H2)
presynaptic inhibition of histamine synthesis and release
regulation of dopamine, GABA, ACh, 5-HT, and NE
17
Q

1st generation H1 receptor antagonist MOA and use

A

reversible, competitive antagonism of H1 receptor
mildly anticholinergic–> ANTI-SLUDE
used as adjuvant to epi in anaphylaxis, allergies, sedation, prevetion N/V, motion sickness, vertigo, local anesthetic, antitussive
Will cross BBB

18
Q

1st generation H1 antagonist drugs

A

for allergy- diphenhydramine, hydroxyzine, chlorpheniramine
for motion sickness- cyclizine, dimenhydrenate (dramamine), meclizine (antivert)
for nausea- promethazine

19
Q

1st generation H1 antagonist adverse effects

A

avoid with MOIs (chlorpheniramine)
sedation, dizziness, fatigue, tachycardia, allergic reactions, anti-muscarinic effects
additive with anti-muscarinics and CNS depressants

20
Q

2nd generation H1 receptor antagonist uses

A

anti-allergy therapeutic d/t non-sedating properties

21
Q

Cetirizine adverse effect (TQ)

A

more CNS actions that other 2nd gen antihistamines and therefore NOT recommended for use by pilots

22
Q

2nd generation H1 drugs examples

A

acrivistine, fexofenadine (allegra), loratadine (claritin), cetirizine (zyrtec), desloratadine

23
Q

H2 receptor antagonist used for?

A

to decrease gastric acid production

treatment of GERD

24
Q

H2 receptor antagoinst drugs examples

A

cimetidine, famotadine (pepsid), nizatidine, ranitidine (zantac)

25
Q

Mast cell stabilizers used MOA and use

A

prevent histamine release from mast cells

used in treatment of asthma and allergic rhinitis

26
Q

Mast cell stabilizer adverse effects

A

cough and bitter taste

27
Q

Mast cell stabilizer drug examples

A

cromolyn sodium

nedocromil (mostly eye drops and nasal sprays)

28
Q

Which antihistaines cross BBB?

A

1st gen antihistamines cross BBB and cause sedation

29
Q

What are H2 receptor antagonists primarily used for?

A

treatment of GI disorders b/c they inhibit gastric acid secretion

30
Q

Which drugs are used for prophylaxis of allergic disorders?

A

cromolyn sodium and nedocromil

Pharmacology (15 decks)

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