Do dorzolamide and latanoprost have the same mechanisms of action?

Dorzolamide and Latanoprost Have Different Mechanisms of Action

Dorzolamide and latanoprost work through completely different mechanisms of action to lower intraocular pressure (IOP). 1, 2

Mechanism of Action Comparison

Dorzolamide

• Functions as a carbonic anhydrase inhibitor that decreases aqueous humor secretion 1
• Specifically inhibits carbonic anhydrase II (CA-II) in the ciliary processes of the eye 1
• Reduces aqueous humor formation by slowing the formation of bicarbonate ions, leading to reduced sodium and fluid transport 1
• Results in decreased aqueous humor production, typically providing a 15-20% reduction in IOP 3

Latanoprost

• Acts as a prostanoid selective FP receptor agonist 2
• Primarily works by increasing the outflow of aqueous humor through the uveoscleral pathway 2
• Does not significantly affect the rate of aqueous humor production 4
• Provides superior IOP reduction compared to dorzolamide (8.5 mmHg vs 5.6 mmHg reduction from baseline) 5

Clinical Implications of Different Mechanisms

• The different mechanisms of action make these drugs complementary when used in combination therapy 4
• When added to latanoprost, dorzolamide provides an additional 5.6% IOP reduction due to their different mechanisms 6
• Dorzolamide can be dosed twice daily when used in combination with latanoprost without significant loss of efficacy compared to three-times-daily dosing 7
• Latanoprost's once-daily dosing regimen offers better compliance compared to dorzolamide's multiple daily dosing requirement 5

Treatment Algorithm Considerations

1. First-line therapy: Prostaglandin analogs (including latanoprost) are recommended as first-line agents due to:

   • Superior efficacy in IOP reduction 3, 8
   • Once-daily dosing improving adherence 5
   • Better overall tolerability profile 8

2. Second-line or adjunctive therapy: Dorzolamide is often used as:

   • An alternative first-line agent when prostaglandins are contraindicated 3
   • An adjunctive therapy to prostaglandins when additional IOP reduction is needed 6

3. Combination therapy: When monotherapy is insufficient:

   • The combination of latanoprost and dorzolamide provides additive IOP-lowering effects due to their complementary mechanisms 4, 9
   • Latanoprost combined with dorzolamide has been shown to be more effective than either agent alone 9

Common Pitfalls to Avoid

• Do not assume that all glaucoma medications work through the same mechanism - this could lead to suboptimal treatment choices 3
• Avoid prescribing multiple medications with the same mechanism of action, as this limits additive benefit 4
• When using combination therapy, space administration of different eye drops by at least 5 minutes to prevent washout 10
• Be aware that dorzolamide requires multiple daily doses for optimal effect, while latanoprost is administered once daily 5