Allergic Rhinitis: Antihistamines

Question 1

What is allergic rhinitis?

Answer 1

A symptomatic disorder of the nose resulting from an IgE-mediated immunological reaction following exposure to allergen.

Question 2

what are the major symptoms of allergic rhinitis?

Answer 2

1. rhinorrhea
2. nasal itching
3. congestion/ obstruction
4. sneezing

Question 3

two ways we can reverse the effects of allergic rhinitis?

Answer 3

1. spontaneously i.e. remove allergen

2. give treatment

Question 4

Explain the mechanism of how allergic rhinitis occurs?

Answer 4

stimulus: genetic sensitivity to stimulus results in allergic reaction.
Chemotaxis: trans-endothelial migration of chemocytes:
1. eosinophils,
2. mast cell precursors,
3. macrophages,
4. langerhan cells and
5. lymphocytes,
which are all activated and remain in the infected area for a long time. IgE is synthesised and forms cross-links with the allergen triggering hypersensitivity. Histamine, tryptase, prostaglandins, leukotrienes are all released.
Response:
-sneezing and nasal itching
-vasodilation
- up-regulation of adhesion molecules (blockage)

Question 5

Four diagnostic tests to test for allergic rhinitis are..?

Answer 5

1. rhinoscopy
2. allergy tests
3. cytology of nasal secretions
4. CT scans

Question 6

6 noticeable physical effects of allergic rhinitis?

Answer 6

1. red/irritated nose
2. blocked nose
3. clear mucus
4. nasal endothelial tissue may be boggy
5. tendered sinuses
6. red eyes

Question 7

how do we treat allergic rhinitis?

Answer 7

1. avoid the allergen

2. pharmacotherapy

Question 8

Three examples of pharmacotherapy are…?

Answer 8

1. mast cell stabilisers
2. steroids
3. antihistamines

Question 9

give an example of a mast cell stabiliser and how does it work?

Answer 9

sodium cromoglicate is an eye drop given to decrease histamine release from mast cells and decrease release of other inflammatory agents.

Question 10

give an example of a steroid and how does it work?

Answer 10

beclomethasone is a corticosteroid nasal spray with more effect for nasal symptoms than antihistamines do. Should blow nose before use to clear away mucus.

Question 11

How are the three anthistamines?

Answer 11

1. H1 receptor antagonist
2. H2 receptor antagonist
3. H3 receptor antagonist

Question 12

How do first generation H1 receptor antagonists work?

Answer 12

have three effects:

1. sedating (help sleep)
2. antiemtic (helps nausea and vomiting)
3. vertigo (help dizziness/imbalance)

Question 13

what are the two types of H1 receptor antagonists?

Answer 13

1st generation and 2nd generation

Question 14

what are the properties of 1st generation H1 antagonists?

Answer 14

• lipid soluble
• well absorbed
• metabolised in liver
• half-life of 5/6 hrs

Question 15

side effects of 1st gen H1 antagonists?

Answer 15

-drowsiness
-headache
-nausea and emesis
-cough
anti-muscarinic effect

Question 16

what happens if you overdose on H1 antihistamines?

Answer 16

• fever
• excitement
• dilated pupils
• hallucinations
• convulsion

Question 17

How do second generation H1 receptor antagonists work?

Answer 17

they avoid drowsiness and only treat symptoms related to the allergy

Question 18

properties of 2nd gen H1 receptor antagonists?

Answer 18

• lipid soluble
• less CNS penetration (more selective for peripheral H1 antagonism)
• well absorbed
• metabolised in liver
• half-life of 5/6hrs

Question 19

what are the side effects of 2nd generation H1 antagonists?

Answer 19

• sedative effect but not as much as 1st gen
• anti-muscarinic effect
• QT prolongation (increases Q-T time in ECG trace - arrhythmia)

Question 20

what is the most commonly used 2nd gen H1 receptor antagonist (aka non-sedating antihistamine)?

Answer 20

Loratidine

Question 21

what drug works as both a mast cell stabilizer and an anti-muscarinic?

Answer 21

Cetirizine