This document discusses various drug treatments for ocular allergies. It describes how allergic reactions cause the release of histamine and other inflammatory mediators from mast cells. The main classes of anti-allergy drugs discussed are ocular decongestants, antihistamines, mast cell stabilizers, NSAIDs, and corticosteroids. Specific examples of drugs in each class are provided along with their mechanisms of action and recommended dosages.

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2.  Release of histamine, prostaglandins, leukotriene and other
less well-defined mediators from the mast cell during an
allergic reaction can cause a variety of uncomfortable
symptoms and sometimes life threatening complications.
 Type 1 hypersensitivity reactions/anaphylactic/immediate or
IgE mediated reactions
 First antigen exposure-IgE antibodies produced and attach
to mast cells
 Second exposure to the same-Degranulation of mast cells
 Release of large quantities of inflammatory mediators
including histamine

3.  Histamine activates H1 receptors on blood vessels-vasodilation-
Leakage of fluid-swelling of tissues-Redness, swelling and
itching
 In Hay fever, allergic conjunctivitis, vernal conjunctivitis, atopic
conjunctivitis, GPC, asthma, bee stings, toxin sensitivities
Treatments:
 Based on the symptoms, severity & characteristics.
 Begins with eliminating & avoiding the allergen.
 Lubricating drops may wash away the allergen.
 Drug intervention required.

4. Main classes of anti-allergy drugs
1. Ocular Decongestants
2. Antihistamines
3. Mast Cell Stabilizers
4. NSAIDS
5. Corticosteroids
6. Other “side” ingredients
1.Ocular Decongestants
 Cost effective choice for mild allergies
 Use with cold compresses
 Artificial tears necessary
 Local vasoconstrictor, temporarily reduces redness
 Does not treat “itching”
 Four alpha-agonists available

5. Ocular Decongestants
 Phenylephrine 0.12% and 0.125%
 Naphazoline (0.012%, 0.05%, 0.1%)
 Tetrahydrozoline(0.05%) Imidazole derivatives
 Oxymetazoline(0.025%)
 All constrict superficial conjunctival vessels within minutes
 Prolonged and excessive use causes rebound conjunctival
hyperemia

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Based on the chemical structure of antihistamine that bind to the receptor
& on the type of histamine antagonist.
 3 types:
 H1, H2 & H3
 H1 receptors located mainly on neuronal tissues and results in itching.
 H2 receptors associated with vascular tissue & results in redness.
 H3 receptors not clinically significant.
 In ocular therapy, mainly H1 antihistamines are applicable.
 H1 antihistamines prevent histamine-H1 receptor interaction
 Thus providing symptomatic relief from histamine activity.

7. 2.Anti-histamines- ocular
 Reduces itching caused from already released histamine from mast cells
and basophils
 Blocks H1 receptors which control
 Itching
 Capillary dilation
 Increase in capillary permeability
 Almost always combined with ocular decongestant
 Chlorpheniramine (does not work as well topically)
 Drugs available
 Levocabastine HCl ophthalmic suspension .05% (Livostin)
 Emedastine difumarate 0.05% (Emadine)
 All QID dosing for 2 weeks

8. Levocabastine
 Highly specific H1 receptor antagonist
 1st antihistamine without a decongestant
 Available as 0.05% suspension. Dosage: 4 times a day
 Emedastine & azelastine are selective H1 receptor antagonists.
 Also inhibit histamine release from mast cells
 Emedastine (0.05% solution) significant reduces itching & redness in 10
minutes of instillation.
 Dosage: 4 times per day. For patients above 3 years of age.

9. 3.Chronic Care Drugs: Mast cell stabilizers
• Stabilizes mast cell membranes and inhibits degranulation of mast cells
• Not effective in acute disease
• Preventive and maintenance therapy
• Must be used regularly for better performance
• VERY, VERY safe
• First generation (older)
• Cromolyn Sodium (Sodium cromoglycate) 4% -BD
• Lodoxaminde 0.1%

10. Chronic Care Drugs: Mast cell stabilizers
• Second generation- BD dosing, same efficacy as first generation
• Pemirolast potassium 0.1% (Alamast)
• Nedocromil sodium 2% (Alocril)
• Pearls to remember:
 Drug of choice for
• Vernal Disease
• GPC
• Chronic allergies
• Children age 3 and above

11. Cromolyn Sodium
• Traditional view was that it inhibits mast cell degranulation & release of
mediators of allergic disease by preventing calcium influx.
• However the mast cell stabilizers containing Cromolyn may also act via
other mechanisms.
• Recent studies showed that it neither exhibits antihistaminic activity nor
inhibit the interaction of IgE with corresponding antigen on the mast cell
surface.
• Cromolyn may also prolong the tear breakup time in patients with
chronic conjunctivitis

12.  Effective in treating ocular allergic reactions like vernal conjunctivitis &
keratitis, allergic keratoconjunctivitis & giant papillary conjunctivitis.
 Frequently seen side effects are stinging or burning after instillation.
 Infrequently, conjunctival injection, watery or itchy eyes, dryness around the
eye, puffy eyes and styes can be seen.

13. 4. Anti-histamines combined with Mast cell
stabilizers
 Stabilizes mast cell membranes and controls immediate itching
 Used BD
 Very, very successful and effective
 Names are:
 Olopatadine hydrochloride 0.1% (Patanol)
 Ketotifen fumarate 0.025% (Zaditor)
 Azelastine HCl 0.05% (Optivar)

14. Other drugs for ocular allergies
 5.NSAIDs
 Ketorolac tromethamine 0.5% (Acular)- First NSAID approved for
topical ocular use in seasonal allergic reactions
 It affects prostaglandin synthesis by inhibiting the activity of
cyclooxygenase (responsible for the conversion of arachidonic acid to
prostaglandin).
 Pharmacokinetic data shows that it penetrates the cornea & reaches
concentrations that reduces prostaglandin E levels in the aqueous
humor.
 Plasma level usually below detectable limit in oral administration.

15.  Does not affect IOP, pupillary response or visual acuity.
 Used mainly in acute allergic conjunctivitis
 Dosage: 4 times daily
 Side effects
 Transient stinging & burning occurs frequently
 Allergic reactions & superficial keratitis rarely occurs.
 Contraindications
 In patients wearing contact lenses.
 Patient who have previously exhibited sensitivity to acetylsalicylic acid,
phenylacetic acid derivatives & other NSAIDs.

16. 6.Corticosteroids
Control of inflammatory and immunologic diseases of eye.
Reduction in capillary permeability and cellular exudation.
Inhibition of degranulation of mast cells, basophils and neutrophils.
“Added” ingredients:
 Camphor
 Menthol
Do not underestimate the value of artificial tears and cold
compresses!

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