The costs of treating glaucoma with combinations of topical drugs in Spain.

PURPOSE This study describes the treatment in ordinary clinical practice in Spain of patients with glaucoma with a two-drug combination therapy. The authors present the treatment outcome as endof-period intraocular pressure (IOP) and the calculated direct medical costs over a 2-year period. METHODS Data were extracted retrospectively from patient charts recording the use of all medical resources related to glaucoma. Costs were estimated using unit costs from public sources (2005). Descriptive cost analysis according to combination treatment at baseline was performed. RESULTS The study included 216 patients from 21 centers. Around half of the patients were started on a beta-blocker/prostaglandin analogue combination, while the rest received various other combinations containing either an alpha2-agonist or a carbonic anhydrase inhibitor. Across the seven groups considered, there was a statistically significant difference in the costs of the least and the two most costly groups, while the confidence intervals were overlapping in all other pairwise comparisons. The least costly drug combination was brimonidine/timolol. Assessing IOP at the end of follow-up, all the groups were equally effective (overlapping confidence intervals). In a multivariate regression analysis, the drug combination did not have an independent, significant impact on total direct medical costs, drug costs, or end-of-period IOP. Significant determinants of these variables were surgical interventions and one or more changes of drug combination during the follow-up. CONCLUSIONS Costs are determined by the response to treatment. Inadequate response triggers treatment changes and sometimes eventually surgical interventions, thereby increasing costs significantly.