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|Dorzolamide Hydrochloride/Timolol Maleate

Dorzolamide Hydrochloride/Timolol Maleate

Trade Names:
Cosopt
- Solution 2% dorzolamide, 0.5% timolol

Mechanism of Action

Pharmacology

Inhibits carbonic anhydrase enzyme, reducing rate of aqueous humor formation thus lowering IOP (dorzolamide); reduces elevated and normal IOP via decreasing production of aqueous humor or increasing flow (timolol).

Indications and Usage

Reduction of IOP in patients with ocular hypertension or open-angle glaucoma.

Contraindications

Bronchial asthma; history of bronchial asthma; severe chronic obstructive pulmonary disease; sinus bradycardia; second or third degree atrioventricular block; overt cardiac failure; cardiogenic shock; hypersensitivity to any component of product.

Dosage and Administration

If using other topical ophthalmic drugs, separate each medication by at least 5 min.

Ophthalmic 1 drop in affected eye(s) bid.

Storage/Stability

Store at controlled room temperature. Keep container tightly closed and protected from light.

Drug Interactions

Although not reported with ophthalmic use of dorzolamide, oral administration has caused acid-base and electrolyte disturbances, which may interfere with renal elimination of certain drugs (eg, salicylates).

Potential additive effect on beta blockade.

Possible increased risk of atrioventricular conduction disturbances, left ventricular failure, and hypotension.

Potential additive effect on patients receiving an oral carbonic anhydrase inhibitor.

Possible additive effect with timolol, producing hypotension and bradycardia, which may result in vertigo, syncope, and postural hypotension.

Increased risk of rebound hypertension following clonidine withdrawal may be exacerbated.

With these agents, timolol has an additive effect in prolonging atrioventricular conduction.

Systemic effect of timolol may be potentiated because of increased plasma levels (eg, decreased heart rate).

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

Hypertension; bradycardia; cardiac failure; cerebral vascular accident; chest pain; hypotension; MI; arrhythmias, syncope, heart block, cerebral ischemia, worsening of angina pectoris, palpitations, cardiac arrest, edema, claudication (timolol).

CNS

Dizziness; headache; depression; fatigue; signs and symptoms of myasthenia gravis, somnolence, insomnia, nightmares, behavioral changes, psychic disturbances (eg, confusion), hallucinations, anxiety, disorientation, nervousness, memory loss (timolol).

Dermatologic

Contact dermatitis (dorzolamide); alopecia, psoriasiform rash, exacerbation of psoriasis, pruritus, urticaria (timolol).

EENT

Ocular burning and stinging; conjunctival hyperemia; blurred vision; superficial punctate keratitis; eye itching; blepharitis; cloudy vision; conjunctival discharge, edema, follicles, or infection; conjunctivitis; corneal erosion; corneal staining; cortical lens opacity; cough; dry eyes; eye debris, discharge, pain, tearing, or edema; eyelid erythema, exudates, scales, pain or discomfort; foreign body sensation; glaucomatous cupping; lens nucleus coloration; lens opacity; nuclear lens opacity; pharyngitis; post-subcapsular cataract; sinusitis; visual field defect; vitreous detachment; throat irritation, eyelid crusting, transient myopia (dorzolamide); ptosis, decreased corneal sensitivity, cystoid macular edema, visual disturbances (eg, refractive changes, diplopia), pseudopemphigoid, choroidal detachment after filtration surgery, tinnitus (timolol).

GI

Bitter, sour, or unusual taste; abdominal pain; dyspepsia; nausea; anorexia (timolol).

Genitourinary

Urinary tract infection; urolithiasis; retroperitoneal fibrosis, impotence, Peyronie disease (timolol).

Respiratory

Bronchitis; influenza; upper respiratory infection; respiratory failure; pulmonary edema, bronchospasm (timolol).

Miscellaneous

Back pain; allergic hypersensitivity, asthenia (dorzolamide/timolol); systemic lupus erythematosus, Reynaud phenomenon, cold hands and feet, decreased libido (timolol).

Precautions

Pregnancy

Category C .

Lactation

Undetermined.

Excreted in breast milk.

Children

Safely and efficacy not established.

Cardiac failure

Inhibition of beta-adrenergic receptor blockade may precipitate more severe cardiac failure in patients with diminished myocardial contractility.

Diabetes mellitus

Use with caution; beta-adrenergic blocking agents may mask the signs and symptoms of acute hypoglycemia.

Major surgery

Some patients receiving beta-adrenergic receptor blocking agents have experienced protracted severe hypotension during surgery.

Thyrotoxicosis

Beta-adrenergic blocking agents may mask certain signs of hyperthyroidism (eg, tachycardia); abrupt withdrawal of agent may precipitate thyroid storm.

Overdosage

Symptoms

Electrolyte imbalance, acidotic state, dizziness, headache, shortness of breath, bradycardia, bronchospasm; cardiac arrest, possible CNS effects.

Patient Information

• Explain name, dose, action, and potential side effects of drug.
• Advise patient that usual dose is 1 drop in the affected eye(s) bid.
• Teach patient proper technique for instilling eye drops: wash hands; do not allow dropper to touch eye. Tilt head back, look up; pull lower eyelid down; instill prescribed number of drops. Close eye for 1 to 2 min and apply gentle pressure to bridge of nose for 3 to 5 min. Do not rub eye.
• Advise patient that if > 1 topical ophthalmic drug is being used, administer the drugs ≥ 10 min apart.
• Inform patients that taste abnormalities (eg, bitter, sour, unusual taste) and burning or stinging of the eye are the most common side effects. Inform patients to contact their health care provider if side effects occur and are bothersome.
• Advise patients who wear contact lenses to remove their lenses before instilling this medicine and to wait ≥ 15 min after instilling eye drop before inserting their lenses.
• Advise patients to contact their eye care physician if eye or eyelid inflammation is noted or if they injure their eye or are going to have surgery on their eye.
• Remind patient that eye examinations and measurement of IOP will be necessary while using this medication and to be sure to keep appointments.