A double masked comparison of the intraocular pressure reducing eVect of latanoprost 0.005% and 0.001% administered once daily in open angle glaucoma and ocular hypertension

Aim—To compare the intraocular pressure (IOP) reducing eVect of latanoprost 0.005% and 0.001%. Methods—Twenty four patients with glaucoma or ocular hypertension were randomised into two groups. Twelve patients (group 1) were given latanoprost 0.005% once daily for 4 weeks and then latanoprost 0.001% once daily for the following 4 weeks. Twelve patients (group 2) were given latanoprost 0.001% once daily for 4 weeks and then latanoprost 0.005% for the following 4 weeks. Results—There was a significant IOP reduction from baseline in both groups on day 28 as well as on day 56. When the results from both groups were used for calculations, the mean IOP reduction from baseline after 4 weeks of treatment with latanoprost 0.005% (day 28 or 56) was 9.6 (SD 3.3) mmHg (35.0%). After 4 weeks of treatment with latanoprost 0.001%, the IOP reduction (day 28 or 56) was 7.6 (3.4) mm Hg (27.7%). The diVerence in IOP reduction between the two concentrations was 2.0 (2.3) mm Hg (p<0.001). Conclusions—Latanoprost 0.005% was more eVective than latanoprost 0.001% in reducing IOP. Even the lower concentration was surprisingly eVective, and potentially may be of importance for use in clinical practice. Furthermore, it is at present unknown whether the increase in iris pigmentation seen in certain patients treated with latanoprost 0.005% is dose dependent and might be less pronounced with latanoprost 0.001%. Long term studies with a larger number of patients are required in order to answer this question. (Br J Ophthalmol 1997;81:867–870) The prostaglandin (PG) analogue latanoprost (PhXA41) and its epimeric mixture PhXA34 have been shown to reduce intraocular pressure (IOP) eVectively in normal, ocular hypertensive and glaucomatous eyes. Latanoprost is a selective FP receptor (PGF2á) agonist. The main mode of action of PGF2á and latanoprost is an increase in uveoscleral outflow of aqueous humour. 10 No significant eVect on aqueous humour production has been found. 12 Alm et al found no clear dose response relation for the IOP reducing eVect of latanoprost when tested at concentrations of 35 μg/ml, 60 μg/ml, and 115 μg/ml when given twice daily for 1 month to patients with primary open angle glaucoma (POAG), capsular glaucoma, or ocular hypertension. The variation in IOP response was, however, largest at the lowest concentration. Racz et al found the duration of action of latanoprost to be more than 24 hours. Administration of latanoprost 0.006% once daily was found to be at least as eVective and apparently superior to the twice daily dose regimen. 8 This raises the question of whether it is possible to further reduce the concentration of latanoprost and still obtain a clinically useful IOP reducing eVect, as discussed also by Camras in his published comment following the paper by Alm et al. Conjunctival hyperaemia, which is observed as a side eVect of certain PGs, does not seem to be a clinical problem when latanoprost is given once daily at a concentration of 0.005%. However, changes in iris colour have recently been reported in some patients treated with latanoprost 0.005% given once daily for more than 3 months. Increased iris pigmentation developed in some eyes with mixed iris colour (hazel, green-brown, or blue-brown). Studies in monkeys seem to indicate that such iris pigmentation may be dose dependent (J Stjernschantz, personal communication). If so, it may be of value to test latanoprost at lower concentrations than 0.005% regarding IOP reduction as well as eVects on iris pigmentation. The present study was designed to compare the IOP reducing eVect of latanoprost 0.005% and 0.001%, respectively, administered once daily. Patients and methods