Combination therapy
When a single therapy is not sufficient to lower the IOP, a combined treatment is indicated. The combination therapy is also dependent upon the mechanism through which the components act to reduce IOP. When choosing an agent for combination therapy, it should be borne in mind that those drugs with complementary mechanisms of action usually work together. Fixed-combination products have the combined efficacy of two ocular hypotensive drugs and the convenience of a two-drug treatment regimen in a single container, which may aid patient adherence to treatment. If a beta-blocking agent is used as an initial treatment, adding a topical CAI can provide an additional reduction in IOP.[84] Another combination product comprises 0.005% latanoprost and 0.5% timolol. The addition of latanoprost to timolol treatment produces an additional IOP reduction of 13-37%, depending upon the frequency of the application and the baseline IOP. Available fixed-combination products consist of timolol 0.5% as an invariant, with brimonidine 0.2%, dorzolamide 2%, travaprost 0.004%, latanoprost 0.005% or bimatoprost 0.03%.[85]
The range of reported additional reductions in IOP, compared to a latanoprost monotherapy baseline are as follows: latanoprost-timolol (13-37%), latanoprostpilocarpine 2% (7-14%), latanoprost and carbonic anhydrase inhibitors (15-24.1%), and latanoprost and dipivefrin (15-28%).[86]
Brimonidine 0.2% combined with 0.5% timolol is the newest fixed combination product in the market. Clinical trials have demonstrated that dorzolamide/timolol (1 drop per eye twice daily) is an effective and generally well-tolerated fixed combination for lowering IOP in patients with open angle glaucoma or OH, including individuals uncontrolled on β -adrenoceptor antagonist monotherapy.[87]