Antihistaminics Flashcards
(37 cards)
Describe histamine’s biological effects.
- Promotes vascular permeability: runny nose, watery eyes, swollen lids, papillae
- Induces vasodilation: redness, headache, hypotension, reflex tachycardia
- Causes smooth muscle contraction: bronchoconstriction
- Stimulates sensory nerves: pain & itching, sneezing
True or false: Antihistaminics are inverse agonists.
True.
What is the most common site of ocular allergy?
Conjunctiva.
- Followed by lids and then the cornea.
Describe the characteristics of Innate Immune response.
- Non-specific and acute
- Lacks memory
- Non-classical complement cascade pathway (no antibodies)
- Common to most life forms
- Involves killer T cells and Macrophages
- Occurs in less than 12hrs
Describe the characteristics of Adaptive Immune response.
- Requires prior exposure to the antigen
- Is an specific and has memory
- Activates classical cascade pathway
- Found exclusively in jawed vertebrates
- Involves cloned memory B&T cells
- 1-2 weeks response time
- will cause a more robust response upon subsequent exposure.
Define Antigen.
Foreign substances having the capacity to
evoke an immunological response
True or False: Types I & IV hypersensitivity are most commonly associated with ocular reactions.
True.
In type 1 hypersensitivity, how long after re-exposure does hypersensitivity reaction occur?
5-30min
*in the initial stage of exposure, activation of cloned B cells occurs in 3-6 days. After re-exposure, hypersensitivity rxn occurs in 5-30minutes.
True or False: Innate Immune Response is the basis for vaccinations.
False. Adaptive Immune Response (which involves antibodies) is the basis for vaccinations.
Give 4 examples of type 4(delayed) hypersensitivity.
- PPD test
- conjunctivitis medicamentosa,
- contact dermatitis,
- chronic graft rejection,
- Type-1 diabetes,
- multiple sclerosis,
- latex
True or False: Type 4 hypersensitivity responds well to antihisaminics.
FALSE!
- Type 4 is NOT responsive to antihistamines
- This is because it is antibody independent. (it is T cell based hypersensitivity)
How long does it take a type 4 hypersensitivity to occur?
2-3 days
True or False: Decongestants are adrenergic agonists.
True
-They cause vasoconstriction.
Why is phenylephrine not commonly used in allergy therapy?
Phenylephrine is not commonly used in allergy therapy due to it’s predilection to produce rebound congestion and, with chronic use, conjunctival medicamentosa
What are the adverse reactions of decongestants?
*General reactions Blur, epithelial erosions, rebound congestion, upper lid retraction *Mydriasis Phenylephrine & Naphazoline *Elevated IOP Naphazoline *Reduced IOP Tetrahydrozoline
What is the only stand alone exception of a topical antihistamine drug?
Emadine (Emadastine)
-Which is a 2nd generation antihistamine.
What are the broader opthalmic indications of antihstamines?
- Allergic conjunctivitis (mild - moderate)
- Myokymia (unilateral spasm of eyelids)
- Allergic rhinitis (sinus)
- Intra-operative anti-miotic
True or False: Dry eyes is one of the adverse reactions of Emedastine (the only stand alone topical antihistamine)
True
What are the serious adverse reactions of Emedastine?
-Keratitis, corneal infiltrates
What drugs do topical antihistamines + Decongestants interact with?
MAOI, EtOH
Name the contraindications of antihistamines + Decongestants topicals.
- Hypersensitivity (topical > oral)
- CVD, DM
- Narrow anterior chamber angles
- Dry eye
How do mast cell stabilizers work?
They are are believed to block Ca++ influx that stimulates degranulation; this effects not only mast cells but other immune cells.
True or Flase: all antihistamines + decongestants topicals are 1st generation antihistamines and all are pregnancy category c and dosing is 4x a day.
True.
True or False: Mast cell stabilizers halt type-1 hypersensitivity reaction.
True: mast cell stabilizers halt type-1 hypersensitivity reaction.
*Because of this they are usually used as a prophylaxis for allergy season.
