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Dorzolamide: Systemic effect: Dorzolamide is sulfonamides and, although administered topically, are absorbed systemically. Therefore, the same types of adverse reactions attributable to systemic sulfonamides may occur with topical administration of this agent. Fatalities have occurred, although rarely, because of 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 re-administered regardless of the route of administration. If signs of serious reactions or hypersensitivity occur, discontinue the use of this preparation.
Corneal endothelium effects: Carbonic anhydrase activity has been observed in both the cytoplasm and around the plasma membranes of the corneal endothelium. The effect of continued administration of dorzolamide on the corneal endothelium has not been fully evaluated.
Acute angle-closure glaucoma: The management of patients with acute angle-closure glaucoma therapeutic interventions in addition to ocular hypotensive agents. Dorzolamide have not been studied in patients with acute angle-closure glaucoma.
Ocular effects: Local ocular adverse effects, primarily conjunctivitis and lid reactions, were reported with chronic administration of dorzolamide. Many of these reactions had the clinical appearance and course of an allergic-type reaction that resolved upon discontinuation of drug therapy. If such reactions are observed, discontinue the drug and evaluate the patients before considering restarting the drug.
Concomitant oral carbonic anhydrase inhibitors: There is a potential for an additive effect on the known systemic effects of CA inhibition in patients receiving an oral CA inhibitor and dorzolamide. Concomitant administrative of ophthalmic and oral CA inhibitors is not recommended.
Bacterial keratitis: There have been reports of bacterial keratitis associated with the use of topical ophthalmic products in multiple-dose containers. These containers had been inadvertently contaminated by patients who, in most cases, had a concurrent corneal disease or a disruption of the ocular epithelial surface. Serious damage to the eye and subsequent loss of vision may result from using contaminated solutions.
Excipients: Benzalkonium chloride has been reported to cause eye irritation, symptoms of dry eyes and may affect the tear film and corneal surface. Should be used with caution in dry eye patients and in patients where the cornea may be compromised. Patients should be monitored in case of prolonged use.
Contact lenses: The preservative used in this product, benzalkonium chloride, may be absorbed by soft contact lenses. Do not administer these agents while wearing soft contact lenses; reinsert lenses 15 minutes or longer after drug administration.
Timolol: Systemic absorption: It may be absorbed systemically. The same adverse reactions found with systemic β-blockers may occur with topical use. For example, severe respiratory reactions and cardiac reactions, including death due to bronchospasm in asthmatics, and rarely, death associated with cardiac failure, have been reported with topical β-blockers.
Cardiovascular: Timolol may decrease resting and maximal exercise heart rate even in healthy subjects.
Non-allergic bronchospasm: Patients with a history of chronic bronchitis, emphysema, etc, should receive β-blockers with caution; they may block bronchodilation produced by catecholamine stimulation of β2-receptors.
Major surgery: Withdrawing β-blockers before major surgery is controversial. Beta-receptor blockade impairs the heart's ability to respond to β-adrenergically mediated reflex stimuli. This may augment the risk of general anesthesia. Some patients on β-blockers have had protracted severe hypotension during anesthesia. Difficulty restarting and maintaining heartbeat has been reported. In elective surgery, gradual withdrawal of β-blockers may be appropriate.
Diabetes mellitus: Administer with caution to patients subject to spontaneous hypoglycemia or to diabetic patients (especially labile diabetics). Beta-blocking agents may mask signs and symptoms of acute hypoglycemia.
Thyroid: Beta-adrenergic blocking agents may mask clinical signs of hyperthyroidism (eg. tachycardia). Manage patients suspected of developing thyrotoxicosis carefully to avoid abrupt withdrawal of β-blockers, which might precipitate thyroid storm.
Cerebrovascular insufficiency: Because of potential effects of β-blockers on blood pressure and pulse, use with caution in patients with cerebrovascular insufficiency. If signs or symptoms suggesting reduced cerebral blood flow develop, consider alternative therapy.
Angle-closure glaucoma: The immediate objective is to reopen the angle, requiring constriction of the pupil with a miotic. These agents have little or no effect on the pupil. When they are used to reduce elevated IOP in angle-closure glaucoma, use with miotic.
Muscle weakness: Beta-blockade may potentiate muscle weakness consistent with certain myasthenic symptoms (eg. diplopia, ptosis, generalized weakness). Timolol has increased muscle weakness in some patients with myasthenic symptoms or myasthenia gravis.
Long-term therapy: In long-term studies (2 and 3 years), no significant difference in mean IOP were observed after initial stabilization.
Effects on ability to drive and use machine: No information.
Use in Children: Safety and efficacy in children have not been established.
Use in Elderly: Dorzolamide: Of all the patients in dorzolamide clinical studies, 44% were 65 years of age or older, and 10% were 75 years of age or older. No overall differences in efficacy or safety were observed between these patients and younger patients, but greater sensitivity of some older individuals to the product cannot be ruled out.
Timolol: Safety and efficacy were similar in patients 65 years of age or older compared with younger patients, however, the possibility that some older patients may exhibit increased sensitivity to the preparation cannot be ruled out.
