Anti-allergic(ocular drugs)

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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

6. HHiissttaammiinnee RReecceeppttoorrss
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!

17. TTHHAANNKK YYOOUU