Dorzolamide and timolol: uses, appearance and warnings

Dorzolamide hydrochloride and timolol maleate ophthalmic solution is indicated for the reduction of elevated intraocular pressure (IOP) in patients with open-angle glaucoma or ocular hypertension who are insufficiently responsive to beta-blockers (failed to achieve target IOP determined after multiple measurements over time). The IOP-lowering of dorzolamide hydrochloride and timolol maleate ophthalmic solution administered twice a day was slightly less than that seen with the concomitant administration of 0.5% timolol administered twice a day and 2% dorzolamide administered three times a day [see Clinical Studies (14) ]. Dorzolamide hydrochloride and timolol maleate ophthalmic solution is a combination of dorzolamide hydrochloride, a carbonic anhydrase inhibitor, and timolol maleate, a beta-adrenergic receptor blocking agent, indicated for the reduction of elevated intraocular pressure (IOP) in patients with open-angle glaucoma or ocular hypertension who are insufficiently responsive to beta-blockers. The IOP-lowering of dorzolamide hydrochloride and timolol maleate ophthalmic solution twice daily was slightly less than that seen with the concomitant administration of 0.5% timolol twice daily, and 2% dorzolamide three times daily. (1)

Ophthalmic solution containing dorzolamide 20 mg/mL (2%) equivalent to 22.26 mg/mL of dorzolamide hydrochloride USP, and timolol 5 mg/mL (0.5%) equivalent to 6.83 mg/mL of timolol maleate USP. Ophthalmic solution containing dorzolamide 20 mg/mL (2%) and timolol 5 mg/mL (0.5%). (3)

Dorzolamide Hydrochloride and Timolol Maleate Ophthalmic Solution USP, 2% / 0.5% is a clear, colorless to nearly colorless, slightly viscous solution packed in 10 mL white opaque bottle with white LDPE nozzle and blue color HDPE cap. 10 mL in a 10 mL bottle NDC 65862-946-01 Storage: Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature]. Protect from light.

Dorzolamide hydrochloride and timolol maleate is contraindicated in patients with: Bronchial asthma or a history of bronchial asthma, severe chronic obstructive pulmonary disease. (4.1) Sinus bradycardia, second or third degree atrioventricular block, overt cardiac failure, cardiogenic shock. (4.2) Hypersensitivity to any component of this product. (4.3 , 5.3) 4.1 Asthma, COPD Dorzolamide hydrochloride and timolol maleate ophthalmic solution is contraindicated in patients with bronchial asthma, a history of bronchial asthma, or severe chronic obstructive pulmonary disease [see Warnings and Precautions (5.1) ]. 4.2 Sinus Bradycardia, AV Block, Cardiac Failure, Cardiogenic Shock Dorzolamide hydrochloride and timolol maleate ophthalmic solution is contraindicated in patients with sinus bradycardia, second or third degree atrioventricular block, overt cardiac failure, and cardiogenic shock [see Warnings and Precautions (5.2) ]. 4.3 Hypersensitivity Dorzolamide hydrochloride and timolol maleate ophthalmic solution is contraindicated in patients who are hypersensitive to any component of this product [see Warnings and Precautions (5.3) ] .

Potentiation of Respiratory Reactions Including Asthma (5.1) Cardiac Failure (5.2) Sulfonamide Hypersensitivity (5.3) Obstructive Pulmonary Disease (5.4) Increased Reactivity to Allergens (5.5) Potentiation of Muscle Weakness (5.6) Masking of Hypoglycemic Symptoms in Patients with Diabetes Mellitus (5.7) Masking of Thyrotoxicosis (5.8) Renal and Hepatic Impairment (5.9) Impairment of Beta-Adrenergically Mediated Reflexes During Surgery (5.10) 5.1 Potentiation of Respiratory Reactions Including Asthma Dorzolamide hydrochloride and timolol maleate ophthalmic solution contains timolol maleate, a beta-adrenergic blocking agent; and although administered topically, is absorbed systemically. Therefore, the same types of adverse reactions that are attributable to systemic administration of beta-adrenergic blocking agents may occur with topical administration. For example, severe respiratory reactions, including death due to bronchospasm in patients with asthma, and rarely death in association with cardiac failure, have been reported following systemic or ophthalmic administration of timolol maleate [see Contraindications (4.1) ]. 5.2 Cardiac Failure Sympathetic stimulation may be essential for support of the circulation in individuals with diminished myocardial contractility, and its inhibition by beta-adrenergic receptor blockade may precipitate more severe failure. In patients without a history of cardiac failure continued depression of the myocardium with beta-blocking agents over a period of time can, in some cases, lead to cardiac failure. At the first sign or symptom of cardiac failure, dorzolamide hydrochloride and timolol maleate should be discontinued [see Contraindications (4.2) ]. 5.3 Sulfonamide Hypersensitivity Dorzolamide hydrochloride and timolol maleate ophthalmic solution contains dorzolamide, a sulfonamide; and although administered topically, it is absorbed systemically. Therefore, the same types of adverse reactions that are attributable to sulfonamides may occur with topical administration of dorzolamide hydrochloride and timolol maleate. Fatalities have occurred, although rarely, due to severe reactions to sulfonamides including Stevens-Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anemia, and other blood dyscrasias. Sensitization may recur when a sulfonamide is readministered irrespective of the route of administration. If signs of serious reactions or hypersensitivity occur, discontinue the use of this preparation [see Contraindications (4.3) ]. 5.4 Obstructive Pulmonary Disease Patients with chronic obstructive pulmonary disease (e.g., chronic bronchitis, emphysema) of mild or moderate severity, bronchospastic disease, or a history of bronchospastic disease (other than bronchial asthma or a history of bronchial asthma, in which dorzolamide hydrochloride and timolol maleate is contraindicated) should, in general, not receive beta-blocking agents, including dorzolamide hydrochloride and timolol maleate [see Contraindications (4.1) ]. 5.5 Increased Reactivity to Allergens While taking beta-blockers, patients with a history of atopy or a history of severe anaphylactic reactions to a variety of allergens may be more reactive to repeated accidental, diagnostic, or therapeutic challenge with such allergens. Such patients may be unresponsive to the usual doses of epinephrine used to treat anaphylactic reactions. 5.6 Potentiation of Muscle Weakness Beta-adrenergic blockade has been reported to potentiate muscle weakness consistent with certain myasthenic symptoms (e.g., diplopia, ptosis, and generalized weakness). Timolol has been reported rarely to increase muscle weakness in some patients with myasthenia gravis or myasthenic symptoms. 5.7 Masking of Hypoglycemic Symptoms in Patients with Diabetes Mellitus Beta-adrenergic blocking agents should be administered with caution in patients subject to spontaneous hypoglycemia or to diabetic patients (especially those with labile diabetes) who are receiving insulin or oral hypoglycemic agents. Beta-adrenergic receptor blocking agents may mask the signs and symptoms of acute hypoglycemia. 5.8 Masking of Thyrotoxicosis Beta-adrenergic blocking agents may mask certain clinical signs (e.g., tachycardia) of hyperthyroidism. Patients suspected of developing thyrotoxicosis should be managed carefully to avoid abrupt withdrawal of beta-adrenergic blocking agents that might precipitate a thyroid storm. 5.9 Renal and Hepatic Impairment Dorzolamide has not been studied in patients with severe renal impairment (CrCl <30 mL/min). Because dorzolamide and its metabolite are excreted predominantly by the kidney, dorzolamide hydrochloride and timolol maleate is not recommended in such patients. Dorzolamide has not been studied in patients with hepatic impairment and should therefore be used with caution in such patients. 5.10 Impairment of Beta-Adrenergically Mediated Reflexes During Surgery The necessity or desirability of withdrawal of beta-adrenergic blocking agents prior to major surgery is controversial. Beta-adrenergic receptor blockade impairs the ability of the heart to respond to beta­-adrenergically mediated reflex stimuli. This may augment the risk of general anesthesia in surgical procedures. Some patients receiving beta-adrenergic receptor blocking agents have experienced protracted severe hypotension during anesthesia. Difficulty in restarting and maintaining the heartbeat has also been reported. For these reasons, in patients undergoing elective surgery, some authorities recommend gradual withdrawal of beta-adrenergic receptor blocking agents. If necessary during surgery, the effects of beta-adrenergic blocking agents may be reversed by sufficient doses of adrenergic agonists. 5.11 Corneal Endothelium Carbonic anhydrase activity has been observed in both the cytoplasm and around the plasma membranes of the corneal endothelium. …

The most frequently reported adverse reactions were taste perversion (bitter, sour, or unusual taste) or ocular burning and/or stinging in up to 30% of patients. Conjunctival hyperemia, blurred vision, superficial punctate keratitis or eye itching were reported between 5 to 15% of patients. (6) To report SUSPECTED ADVERSE REACTIONS, contact Aurobindo Pharma USA, Inc., at 1-866-­850-2876 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. …

Potential additive effect of oral carbonic anhydrase inhibitor with dorzolamide hydrochloride and timolol maleate. (7.1) Potential acid-base and electrolyte disturbances. (7.2) Concomitant use with systemic beta-blockers may potentiate systemic beta-blockade. (7.3) Oral or intravenous calcium antagonists may cause atrioventricular conduction disturbances, left ventricular failure, and hypotension. (7.4) Catecholamine-depleting drugs may have additive effects and produce hypotension and/or marked bradycardia. (7.5) Digitalis and calcium antagonists, may have additive effects in prolonging atrioventricular conduction time. (7.6) CYP2D6 inhibitors may potentiate systemic beta-blockade. …