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Pronunciation:

(dor ZOLE a mide)

U.S. Brand Names:

Trusopt®

Synonyms:

Dorzolamide Hydrochloride

Generic Available:

Canadian Brand Names:

Trusopt®

Use:

Lowers intraocular pressure in patients with ocular hypertension or open-angle glaucoma

Pregnancy Risk Factor:

Lactation:

Excretion in breast milk unknown/not recommended

Contraindications:

Hypersensitivity to dorzolamide or any component of the formulation

Warnings/Precautions:

Although administered topically, systemic absorption occurs. Same types of adverse reactions attributed to sulfonamides may occur with topical administration. Chemical similarities are present among sulfonamides, sulfonylureas, carbonic anhydrase inhibitors, thiazides, and loop diuretics (except ethacrynic acid). In patients with allergy to one of these compounds, a risk of cross-reaction exists; avoid use when previous reaction has been severe.

Because dorzolamide and its metabolite are excreted predominantly by the kidney, it is not recommended for use in patients with severe renal impairment (Clcr<30 mL/minute); use with caution in patients with hepatic impairment. Local ocular adverse effects (conjunctivitis and lid reactions) were reported with chronic administration. Many resolved with discontinuation of drug therapy. If such reactions occur, discontinue dorzolamide. Choriodal detachment has been reported after filtration procedures.

Benzalkonium chloride is the preservative in dorzolamide which may be absorbed by soft contact lenses. Dorzolamide should not be administered while wearing soft contact lenses.

Adverse Reactions:

>10%:

Gastrointestinal: Bitter taste following administration (25%)

Ocular: Burning, stinging or discomfort immediately following administration (33%); superficial punctate keratitis (10% to 15%); signs and symptoms of ocular allergic reaction (10%)

1% to 5%: Ocular: Blurred vision, conjunctivitis, dryness, lid reactions, photophobia, tearing

<1%: Choriodal detachment (following filtration procedures), fatigue, headache, iridocyclitis (rare), nausea, rash (rare), urolithiasis, weakness, xerostomia

Postmarketing and/or case reports: Allergic reaction (systemic), angioedema, bronchospasm, dyspnea, epistaxis, eyelid crusting, myopia, paresthesia, pharyngitis, pruritus, urticaria

Overdosage/Toxicology:

Symptoms of overdose include electrolyte imbalance, development of an acidotic state and possible CNS effects

Treatment is symptomatic

Drug Interactions:

Substrate (minor) of CYP2C8/9, 3A4

Salicylates: High-dose salicylate therapy may result in carbonic anhydrase inhibitor accumulation and toxicity including CNS depression and metabolic acidosis; avoid use if possible.

Stability:

Store at room temperature (25°C).

Mechanism of Action:

Reversible inhibition of the enzyme carbonic anhydrase resulting in reduction of hydrogen ion secretion at renal tubule and an increased renal excretion of sodium, potassium, bicarbonate, and water to decrease production of aqueous humor; also inhibits carbonic anhydrase in central nervous system to retard abnormal and excessive discharge from CNS neurons

Pharmacodynamics/Kinetics:

Onset of action: Peak effect: 2 hours

Duration: 8-12 hours

Absorption: Topical: Reaches systemic circulation where it accumulates in RBCs during chronic dosing as a result of binding to CA-11

Distribution: In RBCs during chronic administration

Protein binding: 33%

Metabolism: To N-desethyl metabolite (less potent than parent drug)

Half-life elimination: Terminal RBC: 147 days; washes out of RBCs nonlinearly, resulting in a rapid decline of drug concentration initially, followed by a slower elimination phase with a half-life of about 4 months

Excretion: Urine (as unchanged drug and metabolite, N-desethyl)

Dosage:

Children and Adults: Reduction of intraocular pressure: Instill 1 drop in the affected eye(s) 3 times/day

Administration:

If more than one topical ophthalmic drug is being used, administer the drugs at least 10 minutes apart. Instruct patients to avoid allowing the tip of the dispensing container to contact the eye or surrounding structures. Ocular solutions can become contaminated by common bacteria known to cause ocular infections. Serious damage to the eye and subsequent loss of vision may occur from using contaminated solutions.

Monitoring Parameters:

Monitor serum electrolyte levels (potassium) and blood pH levels; Ophthalmic exams and IOP periodically

Patient Education:

For use in eyes only. If serious or unusual reactions or signs of hypersensitivity occur, discontinue use of the product. If any ocular reactions, particularly conjunctivitis and lid reactions, discontinue use and notify prescriber. If an intercurrent ocular condition (eg, trauma, ocular surgery, infection) occur, immediately seek your prescriber's advice concerning the continued use of the present multidose container. Avoid allowing the tip of the dispensing container to contact the eye or surround structures. Take out contact lenses before using medicine. Lenses can be replaced 15 minutes after medicine is given. Pregnancy precaution: Inform prescriber if you are pregnant.

Dental Health: Effects on Dental Treatment:

No significant effects or complications reported

Dental Health: Vasoconstrictor/Local Anesthetic Precautions:

No information available to require special precautions

Mental Health: Effects on Mental Status:

May cause drowsiness

Mental Health: Effects on Psychiatric Treatment:

None reported

Dosage Forms:

Solution, ophthalmic, as hydrochloride: 2% (5 mL, 10 mL) [contains benzalkonium chloride]

International Brand Names:

Biodrop® (AR); Trusopt® (AR, AT, AU, BE, BR, CA, CH, CL, CR, CZ, DE, DK, ES, FI, FR, GB, GT, HN, HR, HU, IE, IL, IT, LU, MX, NL, NO, NZ, PA, PL, PT, RO, RU, SE, SG, SI, SV, TH, TR, YU, ZA)

References

Biollaz J, Munafo A, Buclin T, et al, "Whole Blood Pharmacokinetics and Metabolic Affects of the Topical Carbonic Anhydrase Inhibitor Dorzolamide,"Eur J Clin Pharmacol, 1995, 47(5):455-60.

Wilkerson M, Cyrlin M, Lippa EA, et al, "Four-Week Safety and Efficacy Study of Dorzolamide, a Novel, Active, Topical Carbonic Anhydrase Inhibitor,"Arch Ophthalmol, 1993, 111(10):1343-50.

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