Dorzolamide

12.1 Mechanism of Action Carbonic anhydrase (CA) is an enzyme found in many tissues of the body including the eye. It catalyzes the reversible reaction involving the hydration of carbon dioxide and the dehydration of carbonic acid. In humans, carbonic anhydrase exists as a number of isoenzymes, the most active being carbonic anhydrase II (CA-II), found primarily in red blood cells (RBCs), but also in other tissues. Inhibition of carbonic anhydrase in the ciliary processes of the eye decreases aqueous humor secretion, presumably by slowing the formation of bicarbonate ions with subsequent reduction in sodium and fluid transport. The result is a reduction in intraocular pressure (IOP). Dorzolamide Hydrochloride Ophthalmic Solution contains dorzolamide hydrochloride, an inhibitor of human carbonic anhydrase II. Following topical ocular administration, Dorzolamide Hydrochloride Ophthalmic Solution reduces elevated intraocular pressure. Elevated intraocular pressure is a major risk factor in the pathogenesis of optic nerve damage and glaucomatous visual field loss.

1 INDICATIONS AND USAGE Dorzolamide Hydrochloride Ophthalmic Solution is indicated in the treatment of elevated intraocular pressure in patients with ocular hypertension or open-angle glaucoma. Dorzolamide Hydrochloride Ophthalmic Solution is a carbonic anhydrase inhibitor indicated for the treatment of elevated intraocular pressure in patients with ocular hypertension or open-angle glaucoma. ( 1 )

2 DOSAGE AND ADMINISTRATION The dose is one drop of Dorzolamide Hydrochloride Ophthalmic Solution in the affected eye(s) three times daily. Dorzolamide Hydrochloride Ophthalmic Solution may be used concomitantly with other topical ophthalmic drug products to lower intraocular pressure. If more than one topical ophthalmic drug is being used, the drugs should be administered at least five minutes apart. The dose is one drop of Dorzolamide Hydrochloride Ophthalmic Solution in the affected eye(s) three times daily. Dorzolamide Hydrochloride Ophthalmic Solution may be used concomitantly with other topical ophthalmic drug products to lower intraocular pressure. ( 2 )

6 ADVERSE REACTIONS The most frequently reported adverse reactions associated with Dorzolamide Hydrochloride Ophthalmic Solution were ocular burning, stinging, or discomfort immediately following ocular administration (approximately one-third of patients). Approximately one-quarter of patients noted a bitter taste following administration. Superficial punctate keratitis occurred in 10 to 15% of patients and signs and symptoms of ocular allergic reaction in approximately 10%. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Sagent Pharmaceuticals at 1-866-625-1618 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. Controlled clinical trials : The most frequent adverse reactions associated with Dorzolamide Hydrochloride Ophthalmic Solution were ocular burning, stinging, or discomfort immediately following ocular administration (approximately one-third of patients). Approximately one-quarter of patients noted a bitter taste following administration. Superficial punctate keratitis occurred in 10 to 15% of patients and signs and symptoms of ocular allergic reaction in approximately 10%. Reactions occurring in approximately 1 to 5% of patients were conjunctivitis and lid reactions [see Warnings and Precautions ( 5.4 )] , blurred vision, eye redness, tearing, dryness, and photophobia. Other ocular reactions and systemic reactions were reported infrequently, including headache, nausea, asthenia/fatigue; and, rarely, skin rashes, urolithiasis, and iridocyclitis. In a 3-month, double-masked, active-treatment-controlled, multicenter study in pediatric patients, the adverse reactions profile of Dorzolamide Hydrochloride Ophthalmic Solution was comparable to that seen in adult patients. 6.2 Post-Marketing Experience The following adverse reactions have been identified during post-approval use of Dorzolamide Hydrochloride Ophthalmic Solution. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure: signs and symptoms of systemic allergic reactions including angioedema, bronchospasm, pruritus, and urticaria; Stevens-Johnson syndrome and toxic epidermal necrolysis; dizziness, paresthesia; ocular pain, transient myopia, choroidal detachment following filtration surgery, eyelid crusting; dyspnea; contact dermatitis, epistaxis, dry mouth and throat irritation.

7 DRUG INTERACTIONS Potential additive effect of oral carbonic anhydrase inhibitor with Dorzolamide Hydrochloride Ophthalmic Solution. ( 7.1 ) Potential acid-base and electrolyte disturbances. ( 7.2 ) 7.1 Oral Carbonic Anhydrase Inhibitors There is a potential for an additive effect on the known systemic effects of carbonic anhydrase inhibition in patients receiving an oral carbonic anhydrase inhibitor and Dorzolamide Hydrochloride Ophthalmic Solution. The concomitant administration of Dorzolamide Hydrochloride Ophthalmic Solution and oral carbonic anhydrase inhibitors is not recommended. 7.2 High-Dose Salicylate Therapy Although acid-base and electrolyte disturbances were not reported in the clinical trials with dorzolamide hydrochloride ophthalmic solution, these disturbances have been reported with oral carbonic anhydrase inhibitors and have, in some instances, resulted in drug interactions (e.g., toxicity associated with high-dose salicylate therapy). Therefore, the potential for such drug interactions should be considered in patients receiving Dorzolamide Hydrochloride Ophthalmic Solution.