Usage
- Dorzolamide is prescribed for the treatment of elevated intraocular pressure (IOP) in patients with ocular hypertension or open-angle glaucoma, including pseudoexfoliative glaucoma. It is often used as monotherapy in patients unresponsive to beta-blockers or in whom beta-blockers are contraindicated, or as adjunctive therapy to beta-blockers.
- Pharmacological Classification: Carbonic anhydrase inhibitor (ophthalmic).
- Mechanism of Action: Dorzolamide inhibits the enzyme carbonic anhydrase II (CA-II) in the ciliary processes of the eye. This inhibition reduces the formation of bicarbonate ions, which in turn decreases the transport of sodium and fluid into the aqueous humor, thus lowering IOP.
Alternate Names
- Dorzolamide hydrochloride
- Brand Names: Trusopt, Trusopt PF (preservative-free)
How It Works
- Pharmacodynamics: Dorzolamide lowers IOP by reducing aqueous humor production. It does not affect pupil size or accommodation.
- Pharmacokinetics:
- Absorption: After topical ophthalmic administration, dorzolamide is absorbed systemically through the cornea. Systemic absorption is low.
- Metabolism: A small portion is metabolized in the liver to an inactive metabolite N-desethyl dorzolamide.
- Elimination: Primarily renal excretion of unchanged drug and metabolite. The elimination half-life is approximately 3 hours.
- Mode of Action: Dorzolamide binds to and inhibits the active site of CA-II in the ciliary processes, preventing the catalytic formation of bicarbonate ions from carbon dioxide and water. This slows down the formation of aqueous humor, leading to lower IOP.
Dosage
Standard Dosage
Adults:
- One drop in the affected eye(s) three times daily when used as monotherapy.
- One drop in the affected eye(s) two times daily when used as adjunctive therapy with a topical beta-blocker.
- If more than one topical ophthalmic drug is being used, the drugs should be administered at least five to ten minutes apart.
Children:
- Safety and efficacy in children have not been definitively established; however, the adult dose is sometimes used in children under the supervision of a doctor. Pediatric dosing must be determined by a doctor.
Special Cases:
- Elderly Patients: Dosage adjustments are generally not necessary.
- Patients with Renal Impairment: Contraindicated in patients with severe renal impairment (CrCl < 30 mL/min). Dose modification is required for moderate renal impairment.
- Patients with Hepatic Dysfunction: No specific dosage adjustments are usually needed.
- Patients with Comorbid Conditions: Use with caution in patients with pre-existing respiratory conditions like asthma or COPD, and cardiovascular conditions like sinus bradycardia or heart block.
Clinical Use Cases
Dorzolamide is primarily used for long-term management of glaucoma and ocular hypertension and not for acute situations like intubation, surgical procedures, mechanical ventilation, ICU use, or emergency conditions.
Side Effects
Common Side Effects
- Ocular burning, stinging, or discomfort
- Bitter taste
- Blurred vision
- Tearing
- Dry eyes
- Foreign body sensation
- Photophobia (sensitivity to light)
Rare but Serious Side Effects
- Allergic reactions (including Stevens-Johnson syndrome and toxic epidermal necrolysis)
- Iritis, uveitis, and choroidal detachment
- Corneal edema
- Vision changes
- Signs of kidney stones
- Blood dyscrasias
Contraindications
- Hypersensitivity to dorzolamide or any component of the formulation (including sulfonamides)
- Severe renal impairment (CrCl < 30 mL/min)
- Patients taking oral carbonic anhydrase inhibitors
Drug Interactions
- Oral carbonic anhydrase inhibitors (e.g., acetazolamide): Increased risk of systemic carbonic anhydrase inhibition.
- High-dose salicylates: Increased risk of acid-base disturbances and salicylate toxicity.
- Topiramate: Additive effects and potential for serious side effects.
Pregnancy and Breastfeeding
-
Pregnancy Safety Category: C (US FDA). There are no adequate and well-controlled studies in pregnant women. Dorzolamide caused fetal vertebral malformations when administered orally to rabbits at high doses. Use only if the potential benefit justifies the potential risk to the fetus.
-
Breastfeeding: It is unknown whether dorzolamide is excreted in human milk. Use with caution while breastfeeding.
Drug Profile Summary
- Mechanism of Action: Carbonic anhydrase II inhibitor, reducing aqueous humor production.
- Side Effects: Ocular burning/stinging, bitter taste, blurred vision. Rarely: severe allergic reactions, vision changes, signs of kidney stones.
- Contraindications: Sulfa allergy, severe renal impairment, concomitant oral carbonic anhydrase inhibitors.
- Drug Interactions: Oral CA inhibitors, high-dose salicylates, topiramate.
- Pregnancy & Breastfeeding: Use with caution; potential fetal risks and unknown excretion in breast milk.
- Dosage: 1 drop in affected eye(s) 3 times daily (monotherapy) or 2 times daily (with beta-blocker).
- Monitoring Parameters: Intraocular pressure (IOP).
Popular Combinations
- Timolol (beta-blocker): Combined with dorzolamide to achieve additive IOP lowering effects.
Precautions
- May cause drowsiness or blurred vision; caution patients about operating machinery or driving.
- Hypersensitivity reactions can occur.
- Remove contact lenses before administration.
- Monitor for signs of corneal edema in at-risk patients.
- Not recommended for use with oral carbonic anhydrase inhibitors.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Dorzolamide?
A: One drop in the affected eye(s) three times daily for monotherapy, or two times daily when used with a topical beta-blocker.
Q2: What are the common side effects of Dorzolamide?
A: Burning, stinging, bitter taste, blurred vision, tearing, dry eyes.
Q3: How does Dorzolamide work?
A: It inhibits carbonic anhydrase II, reducing aqueous humor production and lowering IOP.
Q4: Can Dorzolamide be used during pregnancy?
A: Use with caution during pregnancy only if the potential benefit outweighs the potential risk to the fetus.
Q5: Is Dorzolamide safe for breastfeeding mothers?
A: Use cautiously. It is unknown if it passes into breast milk. Consider the benefit to the mother and the potential risk to the infant.
Q6: What should be done if a dose is missed?
A: Instill the missed dose as soon as remembered, then resume the regular dosing schedule. Do not double the dose.
Q7: What are the contraindications to using Dorzolamide?
A: Severe renal impairment, hypersensitivity to sulfonamides, concomitant use of oral carbonic anhydrase inhibitors.
Q8: Can Dorzolamide be used with other eye drops?
A: Yes, but administer other eye drops at least 5-10 minutes apart.
Q9: How should Dorzolamide be stored?
A: At room temperature, away from light and moisture.
Q10: How long should Dorzolamide be used?
A: As directed by the physician, typically long-term for glaucoma and ocular hypertension.
This information is current as of February 16, 2025, and may change with future updates.
