Carbonic anhydrase inhibitors are sulphonamide related drugs and may give rise to associated side effects especially with systemic treatment e.g. blood disorders.

Topical carbonic anhydrase inhibitors are licensed for use in patients resistant to beta-blockers or those in whom beta-blockers are contra-indicated. They can be used alone or as an adjunct to a topical beta-blocker.

Brinzolamide is the first choice carbonic anhydrase inhibitor for new patients as it is better tolerated. Dual therapy is more beneficial than mono therapy. Systemic side effects are less compared to oral/iv acetazolamide.

Topical monotherapy

Brinzolamide

• Eye drops 10mg/ml (£4.58 = 5ml)

Dose

• Apply twice daily increased to maximum 3 times daily if necessary

Dorzolamide

• Eye drops 20mg/ml (£3.29 = 5ml)
• Multi-dose preservative free eye drops 20mg/ml (£7.08 = 5ml)
• Unit dose preservative free eye drops 20mg/ml (£24.18 = 60 x 0.2ml unit dose)

Dose

• Apply three times daily

Glycerine

• 50% glycerine in water

Topical combination therapy

Brinzolamide/ Brimonidine

• Eye drops, brinzolamide 10mg/ml, brimonidine 2mg/ml (£9.23 = 5ml)

Dose

• Apply one drop twice daily

Brinzolamide/ Timolol

• Eye drops, brinzolamide 10mg/ml, timolol 5mg/ml (£9.28 = 5ml)

Dose

• Apply twice daily

Dorzolamide/ Timolol

• Eye drops, dorzolamide 20mg/ml, timolol 5mg/ml (£4.35 = 5ml)
• Multi-dose preservative free eye drops, dorzolamide 20mg/ml, timolol 5mg/ml (£8.13 = 5ml)
• Unit dose preservative free eye drops, dorzolamide 20mg/ml, timolol 5mg/ml (£18.39 = 60 x 0.2ml unit dose)

Dose

• Apply twice daily

Systemic

Acetazolamide

• Tablets 250mg (£6.09 = 1g daily)
• Modified-release capsules 250mg (£31.10 = 500mg daily)
• Powder for solution for injection 500mg vials

Indications

• Acetazolamide is used as parenteral or oral therapy for acute glaucoma.

Dose

• Standard-release oral or by intravenous injection: 250mg–1g daily in divided doses
• Modified-release: 250mg - 500mg daily

Notes

1. Side effects include paraesthesia, general malaise/fatigue, dizziness, electrolyte imbalance and depression.