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Pharmacology > Anti-histamines > Flashcards

Anti-histamines Flashcards

1
Q

What is histamine produced by? Where is it stored?

A

Produced by mast cells (immune) and certain cells in the gastric mucosa; certain CNS neurons (can fxn as NT). Stored in basophils (immune).

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2
Q

Where does histamine act?

A

On nearby cells.

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3
Q

What is histamine?

A

A small signaling molecule found in many tissues.

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4
Q

What are the 4 types of Histamine receptors?

A

H1, H2, H3, H4.

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5
Q

Which receptors, and how are they affect, are used clinically?

A

H1 and H2 antagonists.

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6
Q

What is a Type 1 hypersensitivity reaction? What is produced in a response to the stimulus?

A

The stimulus isn’t noxious, but still promotes an immune response (allergen). It evokes the production of a specific antibody, IgE.

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7
Q

What does subsequent exposure to a Type 1 hypersensitivity reaction stimulus result in?

A

Subsequent exposure causes mast cell activation.

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8
Q

What are mast cells? What happens when allergens are present?

A

They contain histamine. When antigen binds to antibody IgE, the histamine is released.

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9
Q

What happens if the mast cells in the gastrointestinal tract are activated?

A

Increased fluid secretions, increased peristalsis. Resulting in expulsion of GI tract contents (diarrhea; vomiting).

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10
Q

What happens if the mast cells in the airways are activated?

A

Decreased diameter, increased mucus secretions. Resulting in congestion, and blocking of airways (coughing, phlegm). Also, swelling and mucus secretion in nasal passage.

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11
Q

What happens if the mast cells in the blood vessels are activated?

A

Increased blood flow, increased permeability. Resulting in, increased fluid in tissues, causing an increased flow of lymph to lymph nodes, increased cells and protein in tissues, increased effector response in tissues.

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12
Q

What are the effects of histamine, H1 receptors in the CNS?

A

Increases wakefulness, inhibits appetite, regulates emesis (nausea and vomiting).

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13
Q

What are the effects of histamine, H2 receptors?

A

Increases heart rate and output. Stimulation of gastric acid secretion by parietal cells. Role in vasodilation.

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14
Q

What are two examples of 1st generation anti-histamines?

A

Diphenhydramine (Benadryll) and Doxylamine.

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15
Q

Compared to 2nd generation anti-histamines, are 1st generation anti-histamines more or less lipid soluble?

A

1st generation anti-histamines are more lipid soluble.

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16
Q

Compared to 2nd generation anti-histamines, are 1st generation anti-histamines more or less sedating?

A

1st generation anti-histamines are more sedative.

17
Q

Compared to 2nd generation anti-histamines, are 1st generation anti-histamines more or less likely to effect other nt receptors?

A

1st generation anti-histamines are more likely to have an effect on other nts.

18
Q

What are the pros of newer anti-histamines?

A

Not as lipid soluble, so less CNS effects. They also are a substrate for a transporter that takes molecules out of the blood-brain barrier.

19
Q

What are two examples of 2nd generation anti-histamines?

A

Cetirizine and Loratadine (Claritin.

20
Q

What is the efficacy of 1st vs. 2nd generation anti-histamines in treating allergic diseases?

A

They are about the same.

21
Q

Can someone become tolerant to the sedation resulting from anti-histamines?

A

Yes.

22
Q

What can be used to prevent/treat motion sickness?

A

1st generation anti-histamines.

23
Q

What can used for severe morning sickness?

A

Doxylamine and vitamin B6 (Diclegis).

24
Q

What other receptors can 1st generation anti-histamine drugs affect? What is the result of this?

A

Muscarinic, M1 receptors. This possibly contributes to anti-emetic effects and other side-effects. They can also affect Alpha receptor, leading to orthostasis (feeling of dizziness when getting up).

25
Q

What do 1st generation anti-histamines affect that leads to local anesthetic effects?

A

They block Sodium channels.

26
Q

How are anti-histamines metabolized?

A

By cytochrome P450 in the liver.

27
Q

What is the duration of action of anti-histamines?

A

4-6 hours. Some: 12-24 hours.

28
Q

What is an example of an H2 antagonist?

A

Ranitidine (Zantac).

29
Q

What does Rantidine (Zantac) do? What can it treat?

A

Suppresses nocturnal stomach acid secretion. Used to treat GERD.

Pharmacology (20 decks)

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