Relief for Allergic Eyes?
By William T. Elliott, MD, FACP, and James Chan, PharmD, PhD
Olopatadine hcl ophthalmic solution (Patanol, Alcon) has been approved by the FDA for the treatment of allergic conjunctivitis. It joins levocabastine and ketorolac as available eye drops for this indication. Two similar products, cromolyn and lodoxamide eye drops, are available for vernal conjunctivitis and keratoconjunctivitis. Olopatadine, however, is a unique molecule that has the dual mechanism of stabilizing mast cells and also blocking histamine-1 receptors in the eye. It also has a relatively long half-life that allows for twice-a-day dosing.
Olopatadine is indicated for the temporary prevention of itching of the eye due to allergic conjunctivitis.
Olopatadine is effective at relieving ocular redness and ocular itching in controlled trials using conjunctival allergen challenge.1,2 It has a rapid onset of action (within minutes) and a long duration of action permitting twice daily dosing. The drug is well tolerated, with ocular irritation occurring at an incidence of less than 5%.2 This low incidence suggests that olopatadine is better tolerated in terms of ocular comfort than ketorolac (Acular) or levocabastine (Livostin). Ocular discomfort for these products has been reported to be 15% and 40%, respectively.3,4 Olopatadine is not contraindicated in contact lens wearers (reinsert lens 10 minutes after instillation) and is FDA approved for use in children as young as age 3.2
Headache is the most commonly reported adverse reaction at an incidence of 7%. The effect of the drug has not been evaluated for use beyond 42 days.2
Olopatadine hydrochloride 0.1% is supplied as an ophthalmic solution in 5 cc Drop-tainers. The recommended dose is 1-2 drops in each affected eye twice daily, at an interval of at least 6-8 hours.
Olopatadine has been shown in animal and in vitro studies to act as an antagonist of histamine-1 receptors as well as an inhibitor of the release of histamine and other mediators of inflammation from mast cells. The latter mechanism has been demonstrated using tissue cultures of human conjunctival mast cells.1,2
Olopatadine has a low incidence of side effects and may be better tolerated than ketorolac and levocabastine. No comparative data are available with mast cell stabilizers (cromolyn or lodoxamine) or other antihistamines or antihistamine/decongestants. It also has a rapid onset of action an a long duration of action, allowing for bid dosing.
The drug is competitively priced with newer ophthalmic products for the same indication, but it is much more expensive than older agents.
Olopatadine is a new ophthalmic drop with a unique mode of action for the indication of allergic conjunctivitis. It is conveniently dosed and may be better tolerated than other drugs in this class.