Antihistamines (Rx) Flashcards Preview

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Flashcards in Antihistamines (Rx) Deck (19)
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1
Q

Histamine receptors are ____-type receptors.

A

G-protein coupled receptors.

2
Q

Describe the H1 type histamine receptor.

A

H1 receptors are expressed on SM and endothelium. They are responsible for itch, pain, edema and secretion from the mucosa. (increase IP3 and DAG)

3
Q

Describe the H2 type histamine receptor.

A

H2 receptors are expressed on mast cells, basophils, parietal cells and cardiac muscle. They function in gastric acid secretion, vasodilation and increased heart rate. (increase cAMP).

4
Q

Describe the H3 type histamine receptor.

A

H3 receptors are expressed on presynaptic histaminergic neurons of the brain, the myenteric plexus and other neurons. They inhibit NT release. (decrease cAMP).

5
Q

Describe the H4 type histamine receptor.

A

They are expressed on cells of HSC origin: eosinophils, neutrophils, DCs basophils. They play a role in cytokine secretion and adhesion factor, as well as differentiation. (decrease cAMP)

6
Q

Define how an urticarial response relates to histamine.

A

Urticarial response (H1) is a reaction to stinging insects and plants at peripheral sensory nerve terminals.

7
Q

All first generation H1 antihistamines cause ______ as a side effect. They are primarily used to treat _____.

A

1st generation (H1) antihistamines treat allergy symptoms, but cause drowsiness (sedation) as a side effect.

8
Q

What is the general function of antihistamines?

A

Antihistamines block H1/H2 receptors. They are effective if given before histamine release.

9
Q

How do mast cell degranulation inhibitors work? Provide 2 examples.

A

Inhibitors of mast cell degranulation block Cl- channels and inhibit Ca2+ mobilization to prevent degranulation. They must be inhaled and are used in children to prevent asthma attacks. (ex: Cromolyn and Nedocromil)

10
Q

How does epinephrine function against allergic reactions?

A

Epinephrine is the BEST treatment for anaphylaxis. It counteracts histamine action since it’s an agonist for alpha and beta receptors. Epi-pen injection stimulates bronchodilation and increases BP.

11
Q

List 4 ways that 1st generation (H1) antihistamines differ from 2nd generation.

A

1st gen antihistamines:

  1. neutral at physiologic pH (cross BBB)
  2. Sedative and anti-emetic
  3. short-acting (6-12 hours)
  4. components of OTC treatments for insomnia, itching and nausea
12
Q

List at least 3 examples of 1st generation (H1) antihistamines.

A
  1. Ethanolamines (Benadryl)
  2. Ethylenediamnes (PBZ)
  3. Alkylamines
13
Q

List 3 therapeutic applications of H1 antihistamines.

A
  1. Allergic reaction treatments
  2. Motion sickness, vertigo and insomnia (cross BBB).
  3. Anti-emetics
14
Q

List at least 3 adverse effects of H1 antihistamines.

A
  1. CNS toxicity
  2. anticholinergic effects (dilated pupils, blurred vision)
  3. Drug interactions (use with alcohol or CYP inhibitors)
15
Q

List 3 clinical uses of H2 antihistamines.

A
  1. Hydrophilic (no CNS interactions)
  2. Treats GERD, promotes healing of gastic ulcers.
  3. Very specific (no H1 or H3 interactions)
16
Q

List at least 2 adverse effects of H2 antihistamines.

A
  1. Neurological effects in patients with impaired renal or hepatic functions
  2. Prolonged use can result in indigestion (low stomach acid)
17
Q

Provide 2 examples of 2nd generation (H1) antihistamines

A
  1. Piperazines (Zyrtec)

2. Piperidines (Claritin) and Fexifenadine (Allegra)

18
Q

Describe the method by which antihistamines can be used to treat gastric ulcers.

A
  1. antihistamines inhibit ACh and Gastrin
  2. Calcium and cAMP levels decrease
  3. Lower H+/K+ ATPase function (increase Gastric pH)
19
Q

What drugs are more potent than antihistamines in treating gastric ulcers?

A

Proton-pump inhibitors (PPI’s)