Ocular Anti-al lergy DrugsOcular Anti-al lergy Drugs

Raju KaitiRaju KaitiOptometristOptometrist

Dhulikhel Hospital, Kathmandu University HospitalDhulikhel Hospital, Kathmandu University Hospital

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 l i fe threatening complications.

Type 1 hypersensit ivity reactions/anaphylactic/immediate or IgE mediated reactions

First antigen exposure-IgE antibodies produced and attach to mast cel ls

Second exposure to the same-Degranulation of mast cells

Release of large quantit ies of inflammatory mediators including histamine

Histamine activates H1 receptors on blood vessels-vasodilat ion-Leakage of f luid-swell ing of t issues-Redness, swell ing and itching

In Hay fever, al lergic conjunctivit is, vernal conjunctivit is, atopic conjunctivit is, GPC, asthma, bee st ings, toxin sensit ivit ies

Treatments: Based on the symptoms, severity & characterist ics.

Begins with el iminating & avoiding the allergen.

Lubricating drops may wash away the allergen.

Drug intervention required.

Main classes of anti-al lergy drugs1. 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

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

Histamine ReceptorsHistamine ReceptorsBased 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.

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

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.

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%

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

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

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.

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)

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.

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.

6.CorticosteroidsControl 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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