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J. V. Freudenthal, D. Pericak, D. B. Yan; Relationship Between Patient Tolerability and Efficacy When Switching From Dorzolamide/Timolol to Brimonidine/Timolol Fixed Combination in the Treatment of Open Angle Glaucoma. Invest. Ophthalmol. Vis. Sci. 2010;51(13):169.
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Intolerability to medical therapy in glaucoma may adversely affect patient compliance, thus affecting the quality of the intraocular pressure (IOP) control. The purpose of this study is to determine if patient tolerability is related to the change in IOP when switching from dorzolamide/timolol fixed combination (DTFC) to brimonidine/timolol fixed combination (BTFC) in the treatment of primary open angle glaucoma (POAG).
25 patients were enrolled into an investigator-masked, open-label study, of which 32% were initially treated with DTFC alone at baseline and 68% received DTFC/ prostaglandin analogue adjunctive therapy. Of these 25 patients: 60% were male, 40% female with a mean age of 64.3yrs for both. At baseline (V0), if the IOP at 10am±1hr exceeded 15mmHg, subjects were administered a linear grading scale questionnaire (0=none, 1=mild, 2=moderate, 3=severe) on medication stinging, abnormal taste, blurred vision and overall discomfort, which was masked from the investigator. Total symptom score (TSS) was calculated by summing up the item responses to the 4 questions, with a maximum score of 12. After another 8 weeks on DTFC, IOP was measured again (V1), and patients were then switched to BTFC. At 12 weeks (V2), IOP was measured and the same tolerability questionnaire was re-administered. The effect of switching medications (ΔIOP) was calculated by subtracting the IOP at V1 on DTFC from the IOP at V2 on BTFC.
There was no significant change in IOP while continuing to observe patients on DTFC from V0 to V1 (p=0.2). There was a statistically significant decrease (p=0.037) in IOP from 16.8±2.3mmHg at V1 (on DTFC) to 15.8±2.4mmHg at V2 (on BTFC). TSS was significantly correlated to ΔIOP (p=0.005, ANOVA). This correlation persisted after adjusting for IOP at baseline (p=0.009, ANCOVA). TSS significantly decreased (p<0.0001) from 4.8±2.5 on DTFC (at V0) to 1.8±1.9 on BTFC (at V2). TSS severity at V0 was strongly correlated to the change in TSS from V0 to V2 (Pearson Coefficient=0.7, p<0.0001). Dividing the study group into tertiles based on TSS, ΔIOP = +0.3±1.8 mmHg for the lowest tertile (TSS = 0–3), ΔIOP = –0.4±1.2mmHg for the middle tertile (TSS = 4–5), and ΔIOP = –2.1±1.4mmHg for the highest tertile (TSS ≥ 6).
Patient tolerability is a strong predictor of IOP change when switching medications from DTFC to BTFC, and may be an important consideration to achieve optimum medical therapy in glaucoma.
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