Antihistamines/Mast Cell Stabilizers

Question 1

Type 1 Hypersensitivity pathway

Answer 1

1. Exposure to antigen
2. IgE produced
3. IgE binds to mast cells and basophils
4. Antigen binds to IgE/Mast cell complex
5. Ca2+ influx depolarizes cell resulting in degranulation of mast cells, causing release of histamine
6. Allergy symptoms

Question 2

Antihistamine drugs

Answer 2

H1: Emedastine

Mast Cell Stabilizers:
Cromolyn sodium
Lodoxaminde
Pemirolast
Nedocromil

MSC/Antihistamine Combos:
Bepotastine
Epinastine
Ketotifen (Zaditor/Alaway)
Ololpatidine .1% and .7%
Olopatadine .2% (Pataday)
Azelastine
Alcaftadine (Category B: safe for pregnancy)
^ *FDA approved for ocular itching

Question 3

Antihistamines: MOA

Answer 3

Block type 1 hypersensitivity reactions. Do not block histamine release from mast cells and basophils

Question 4

Antihistamines: Emedastine

1. Drug type
2. Indications
3. MOA
4. SEs and contraindications

Answer 4

1. Antihistamine
2. *Mild/moderate allergic conjunctivitis
3. Block type 1 hypersensitivity
4. N/A

Question 5

Mast Cell Stabilizers: MOA

Answer 5

Acts on exposed mast cells and inhibits degranulation, preventing Ca2+ influx

Question 6

Mast Cell Stabilizers: Indications

Answer 6

Chronic allergic conjunctivitis, vernal/atopic keratoconjunctivitis

Not effective for acute allergy symptoms