Anti_Histamines Flashcards

1
Q

Autacoids

A

endogenous molecules that do not fall into traditional autonomic groups. They do not act on cholinoceptors
or adrenoceptors but have powerful pharmacologic effects on
smooth muscle and other tissues.

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2
Q

Most important amine autacoids

A

Histamine and Serotonin (5-hydroxytryptamine, 5-HT)

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3
Q

Acid-peptic disease

A

The disease of the upper digestive tract caused by acid and pepsin; includes gastroesophageal reflux,
erosions, and ulcers

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4
Q

Carcinoid

A

A neoplasm of the gastrointestinal tract or bronchi that may secrete serotonin and a variety of peptides

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5
Q

Ergotism (“St. Anthony’s

fire”)

A

Disease caused by excess ingestion of ergot alkaloids; classically an epidemic caused by consumption of grain (eg, in bread) that is contaminated by the ergot fungus

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6
Q

Gastrinoma

A

A tumor that produces large amounts of gastrin; associated with hypersecretion of gastric acid and pepsin leading to ulceration

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7
Q

IgE-mediated immediate

reaction

A

An allergic response, for example, hay fever or angioedema, caused by interaction of an antigen
with IgE antibodies on mast cells; results in the release of histamine and other mediators of allergy

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8
Q

Oxytocic

A

A drug that causes contraction of the uterus

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9
Q

Zollinger-Ellison syndrome

A

Syndrome of hypersecretion of gastric acid and pepsin, often caused by gastrinoma; is associated
with severe acid-peptic ulceration and diarrhea

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10
Q

Histamine is synthesized by

A

Histidine

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11
Q

Where is histamine stored?

A

stored in high concentrations in vesicles in mast cells, enterochromaffin cells in the gut, some neurons, and a few other cell types

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12
Q

Histamine is metabolized by the enzymes

A

monoamine oxidase

and diamine oxidase.

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13
Q

Excess production of histamine in the body

A

systemic mastocytosis

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14
Q

How is systemic mastocytosis measured?

A

detected by measurement of its major metabolite, imidazole acetic acid, in the urine. Because
it is released from mast cells in response to IgE-mediated (immediate) allergic reactions,

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15
Q

the pathophysiologic role of Histamine

A

plays a pathophysiologic role in seasonal rhinitis (hay fever), urticaria, and angioneurotic edema. (The peptide bradykinin also plays an important role in
angioneurotic edema

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16
Q

scombroid poisoning

A

Fish that has been stored improperly
generates high concentrations of histamine; consumption of
such fish may produce severe histamine toxicity

17
Q

receptors that have most Histamine actions

18
Q

triple response

A

histamine effect on the skin is mediated mainly by H1 and H2
receptors. This response involves a small red spot at the center of an intradermal injection of histamine surrounded by an edematous wheal, which is surrounded by a red flare.

19
Q

H1

A

Smooth muscle, endothelium, brain Gq; ↑ IP3, DAG

Typical responses include pain and
itching in the skin, bronchoconstriction, and vasodilation, the latter caused by the histamine-evoked release of nitric oxide. Capillary endothelial cells, in addition to releasing nitric oxide (NO) and other vasodilating substances, also contract, opening gaps in the permeability barrier and leading to the formation of local edema.
These effects occur in allergic reactions and in mastocytosis

Diphenhydramine, loratidine

20
Q

H2

A

Stomach, heart, mast cells, brain Gs; ↑ cAMP Cimetidine

This Gs-coupled receptor mediates gastric acid secretion by parietal cells in the stomach. It also has a cardiac stimulant effect. A third action is to reduce histamine release from mast cells—a negative feedback effect.

21
Q

H3

A

Nerve endings, CNS Gi; ↓ cAMP
Clobenpropit

presynaptic modulation of histaminergic neurotransmission in the central nervous system (CNS). Food intake and body weight increase in H3-receptor knockout animals; therefore,
selective H3 agonists are under investigation as appetite suppressants. In the periphery, it appears to be a presynaptic heteroreceptor with modulatory effects on the release of another transmitter

22
Q

H4

A

Leukocytes, CD4-T cells Gi; ↓ cAMP
Thioperamide

is located on leukocytes (especially eosinophils) and mast cells and is involved in chemotactic responses by these cells

23
Q

5-HT1D/1B

A

Brain

Gi; ↓ cAMP

24
Q

5-HT2

A

Smooth muscle, platelets, brain Gq; ↑ IP3, DAG Ketanserin

25
5-HT3
``` Area postrema (CNS), sensory and enteric nerves Ligand-gated Na+/K+channel ``` Ondansetron
26
5-HT4
Presynaptic nerve terminals in the enteric nervous system Gs; ↑ cAMP Tegaserod (partial agonist)
27
H1 blockers, first-generation
``` Diphenhydramine, dimenhydrinate Competitive pharmacologic block of peripheral and CNS H1 receptors plus α- and M-receptor block. Anti-motion sickness effect ``` Hay fever, angioedema, motion sickness • used orally as OTC sleep aid; used parenterally for dystonias Oral, parenteral Duration: 6–8 h Sedation, autonomic block Rare CNS excitation
28
Promethazine:
H1 blocker with less anti-motion sickness action and more sedative and autonomic effects
29
Cyclizine, meclizine
H1 blockers with more anti-motion sickness action and less sedative and autonomic effect
30
Chlorpheniramine
H1 blocker with negligible anti-motion sickness, sedative, and autonomic effects
31
H1 blockers, second generation
Cetirizine Competitive pharmacologic block of peripheral H1 receptors. No autonomic or anti-motion sickness effects Hay fever, angioedema Oral Duration: 12–24 h Minimal toxicities
32
Fexofenadine, loratadine, desloratadine
similar to cetirizine
33
H2 blockers
Cimetidine, famotidine, ranitidine, nizatidine Competitive pharmacologic block. No H1, autonomic, or anti-motion effects Gastroesophageal reflux disease, stress ulcers Oral, parenteral Duration (large doses): 12–24 h Cimetidine: drug interactions; other H2 blockers much less
34
5-HT1 agonists
Sumatriptan 5-HT1D/1B agonist • causes vasoconstriction • modulates neurotransmitter release Migraine and cluster headache Oral, inhaled, parenteral Duration: 2–4 h Paresthesias, dizziness, chest pain • possible coronary vasospasm
35
Almotriptan, eletriptan, frovatriptan, naratriptan, rizatriptan, zolmitriptan
very similar to sumatriptan; oral preparations only; durations: 2–27 h