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Ocular Pharm > Antihistaminics > Flashcards

Antihistaminics Flashcards

1
Q

Describe histamine’s biological effects.

A
  • 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
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2
Q

True or false: Antihistaminics are inverse agonists.

A

True.

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3
Q

What is the most common site of ocular allergy?

A

Conjunctiva.

- Followed by lids and then the cornea.

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4
Q

Describe the characteristics of Innate Immune response.

A
  • 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
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5
Q

Describe the characteristics of Adaptive Immune response.

A
  • 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.
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6
Q

Define Antigen.

A

Foreign substances having the capacity to

evoke an immunological response

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7
Q

True or False: Types I & IV hypersensitivity are most commonly associated with ocular reactions.

A

True.

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8
Q

In type 1 hypersensitivity, how long after re-exposure does hypersensitivity reaction occur?

A

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.

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9
Q

True or False: Innate Immune Response is the basis for vaccinations.

A

False. Adaptive Immune Response (which involves antibodies) is the basis for vaccinations.

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10
Q

Give 4 examples of type 4(delayed) hypersensitivity.

A
  • PPD test
  • conjunctivitis medicamentosa,
  • contact dermatitis,
  • chronic graft rejection,
  • Type-1 diabetes,
  • multiple sclerosis,
  • latex
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11
Q

True or False: Type 4 hypersensitivity responds well to antihisaminics.

A

FALSE!

  • Type 4 is NOT responsive to antihistamines
  • This is because it is antibody independent. (it is T cell based hypersensitivity)
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12
Q

How long does it take a type 4 hypersensitivity to occur?

A

2-3 days

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13
Q

True or False: Decongestants are adrenergic agonists.

A

True

-They cause vasoconstriction.

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14
Q

Why is phenylephrine not commonly used in allergy therapy?

A

Phenylephrine is not commonly used in allergy therapy due to it’s predilection to produce rebound congestion and, with chronic use, conjunctival medicamentosa

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15
Q

What are the adverse reactions of decongestants?

A 
*General reactions
Blur, epithelial erosions, rebound congestion, upper lid retraction
*Mydriasis
Phenylephrine & Naphazoline
*Elevated IOP
Naphazoline
*Reduced IOP
Tetrahydrozoline
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16
Q

What is the only stand alone exception of a topical antihistamine drug?

A

Emadine (Emadastine)

-Which is a 2nd generation antihistamine.

17
Q

What are the broader opthalmic indications of antihstamines?

A
  1. Allergic conjunctivitis (mild - moderate)
  2. Myokymia (unilateral spasm of eyelids)
  3. Allergic rhinitis (sinus)
  4. Intra-operative anti-miotic
18
Q

True or False: Dry eyes is one of the adverse reactions of Emedastine (the only stand alone topical antihistamine)

A

True

19
Q

What are the serious adverse reactions of Emedastine?

A

-Keratitis, corneal infiltrates

20
Q

What drugs do topical antihistamines + Decongestants interact with?

A

MAOI, EtOH

21
Q

Name the contraindications of antihistamines + Decongestants topicals.

A
  • Hypersensitivity (topical > oral)
  • CVD, DM
  • Narrow anterior chamber angles
  • Dry eye
22
Q

How do mast cell stabilizers work?

A

They are are believed to block Ca++ influx that stimulates degranulation; this effects not only mast cells but other immune cells.

23
Q

True or Flase: all antihistamines + decongestants topicals are 1st generation antihistamines and all are pregnancy category c and dosing is 4x a day.

A

True.

24
Q

True or False: Mast cell stabilizers halt type-1 hypersensitivity reaction.

A

True: mast cell stabilizers halt type-1 hypersensitivity reaction.
*Because of this they are usually used as a prophylaxis for allergy season.

25
Q

True or False: nedocromil is the fastest acting topical mast cell stabilizer in chronic care.

A

True
nesocromil (brand name Arocril) by allergan is the fastest acting topical mast cell stabilizer. And dosing is only 2x a day vs 4x a day of the others.
*it is also fairly safe compared to the other MCSs.

26
Q

True or False: MCS (mast cell stabilizers) are less likely to cause contact dematitis.

A

True.

27
Q

True or False: Mast cell stabilizers almost always cause burning/stinging as one of their adverse reactions.

A

True. Burning or stinging is a very common adverse reaction of MCS.

28
Q

Which drug is the only OTC topical antihistamine + MCSs combo?

A

Ketotifen (brand name: Zaditor) *available OTC as Claritin Eye, Refresh, Alaway
is the only OTC topical antihistamine + MCS combo.

29
Q

Upper respiratory infection is an adverse reaction associated with which antihistamine + MCS combo?

A

Elestat

30
Q

When would you use oral vs topical allergy therapy?

A

Oral therapy are;

  • Better for deeper ocular involvement
  • Better for moderate → severe eyelid edema & conjunctival chemosis
31
Q

Which oral antihistamines, 1st generation or 2nd generation are noticeably lipophilic and thus pass through the blood brain barrier?

A

1st generation oral antihistaminics such as Diphenhydramine (aka benadyryl) are lipophilic and easily cross the BBB. This is what gives them their sedative (drowsy) properties- CNS effects.

32
Q

What are the drug interactions for 1st generation oral antihistaminics?

A

Potassium supplements
Codeine & Opioids (cause constipation-additive effect)
Anticholinergics

33
Q

True or False: Angle closure glaucoma is one of the contraindications of oral antihistaminics.

A 
True
Contraindications of antihistaminics include; 
-Peptic ulcer
-Prostatic hypertrophy
-Bladder obstruction
-Angle closure glaucoma
34
Q

True or False: 2nd generation antihistaminics are noticeably less lipohilic than 1st gen oral antihistaminics.

A

True.

35
Q

Which drug is the most potent 2nd gen oral antihistamine.

A

Zyrtec

36
Q

Which 2nd gen oral antihistamine has least CNS effect?

A

Allegra

37
Q

True or False: Lotemax (seroid drug) is safe for long term therapy of SAC (Seasonal Allergic Conjunctivitis) & VKC (vernal keratoconjunctivitis).

A

True.

Ocular Pharm (11 decks)

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