Measurement of adherence to brimonidine therapy for glaucoma using electronic monitoring

To assess the patient adherence and behavior with brimonidine twice daily (bid) or 3 times daily (tid) in patients used to topical glaucoma medication.

Seventy-five patients with glaucoma or ocular hypertension were enrolled in a prospective, observational cohort study. Consenting patients were randomly assigned to brimonidine bid or tid and received conventional brimonidine eye drops with attached electronic monitoring devices for 4 weeks. Patients were not explicitly informed on the compliance monitoring.

The study was completed by 67 patients (89%). In 65 patients (97%), at least 1 dosing interval exceeded 24 hours. The mean adherence rates were better in the brimonidine bid group (72 ± 19% vs. 62 ± 16%, P=0.04), although dosing frequency was higher in the tid group (1.9 ± 0.5 vs. 1.4 ± 0.4 per day; P<0.001). On average medication coverage was 70% for the bid group and 67% for the tid group; 19 patients (28%) had a coverage rate above 75%, 42 patients (63%) 50% to 75%, and 6 (9%) below 50%. Patients with normal-tension glaucoma had lower coverage rates than patients with primary open-angle glaucoma and ocular hypertension (P<0.05). Data also showed that on average 20% of the glaucoma medication was wasted owing to inefficient drug delivery by using more than 1 drop per dosing.

Individual adherence with brimonidine was highly variable and pharmacologically insufficient for more than two-third of the patients. Special attention should be paid to compliance of patients with normal-tension glaucoma. Our findings underline the need to improve individual adherence and drug delivery in topical glaucoma therapy.