As a member of the prostamide class of ocular hypotensives, bimatoprost (Lumigan®) lowers intraocular pressure (IOP) by a dual mechanism: by increasing both pressure-dependent (presumed trabecular meshwork) and pressure-independent (presumed uveoscleral) outflow. In recent clinical trials, once-daily bimatoprost substantially reduced IOP.
Latanoprost (Xalatan®) is a prostaglandin analogue that reduces IOP primarily by increasing aqueous outflow through the uveoscleral pathway. Clinical trials have shown latanoprost to be less effective than bimatoprost in reducing mean IOP and have suggested that many patients may not respond to latanoprost. In a recent comparison with bimatoprost, 38% to 50% of latanoprost-treated patients were non-responders (response defined as an IOP reduction of ≥20%). In clinical practice, inability to achieve a clinically relevant IOP reduction with an ocular hypotensive from one class usually signals the advisability of a switch to an agent from a different class. Arecent study has demonstrated that bimatoprost effectively lowers IOP in patients unresponsive to latanoprost.
Bimatoprost may also be useful as additive or replacement therapy in patients already receiving maximally tolerated doses of latanoprost. The purpose of this study was to determine whether bimatoprost lowers IOP in patients with glaucoma or ocular hypertension who are not responsive to latanoprost.
This open-label, monocular study enrolled men and women, at least 18 years of age, with a clinical diagnosis of primary open-angle glaucoma or ocular hypertension in both eyes. All participants affirmed their ability to follow instructions and complete all required visits. Major exclusion criteria were current use of latanoprost or bimatoprost; sensitivity/ allergy to any component of either medication; pregnancy, planned pregnancy, breast feeding, or nonuse of a reliable birth control method among women of child-bearing potential; and ocular surgery within the past 3 months. The study was conducted in accordance with the Declaration of Helsinki and with applicable Institutional Review Board regulations (US Code of Federal Regulations, 21, part 56.103). Participants gave informed consent prior to initiation of any study-related procedures, and the study complied with informed consent regulations (US CFR, 21, part 50).
Intervention and Outcome Measures
All patients considered for enrollment were screened for eligibility by means of external, visual-field, and dilated fundus examinations as well as visual-acuity, slitlamp, and gonioscopic testing. Acomplete medical history was taken. Following written informed consent, patients using ocular hypotensive medications completed a 4-week washout. Abaseline visit was then scheduled, at which the external and slitlamp examinations and visual acuity measurements were repeated. When IOP was determined at 10 AM, patients with an untreated level between 22 and 34 mm Hg in at least one eye were given latanoprost .005% and instructed to instill one drop in that eye or, if both eyes qualified, in the eye with the higher IOP before going to bed each night. The eye with the lower IOP was not treated to provide an internal control. If the IOP was identical in both eyes, the right eye was selected for treatment. Study visits were divided into two 8-week phases (Fig 1). During phase 1, patients not responsive to latanoprost were identified. During phase 2, the IOP-lowering efficacy of bimatoprost in nonresponders to latanoprost was evaluated.
Of the 51 patients screened for inclusion, 21 continued to phase 2 and completed the study as planned. Patients ranged in age from 38 to 86 years. One patient was lost to follow-up and 1 withdrew consent prior to starting phase 1. All had a diagnosis of open-angle glaucoma. Most patients were female (15/21, 71.4%) and white (18/21, 85.7%).
Robert D. Williams. Advances In Therapy. Volume 19 No. 6 November/December 2002