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Editors Selection IGR 11-1

Medical Therapy: Fixed vs. unfixed combination therapy

Comment by Luca Rossetti on:

26724 A 12-week, randomized, double-masked study of fixed combination latanoprost/timolol versus latanoprost or timolol monotherapy, Palmberg P; Kim EE; Kwok KK et al., European Journal of Ophthalmology, 2010; 20: 708-718

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Fixed combinations have several potential advantages over unfixed combined therapies, and improvement of compliance is perhaps the most attractive. When fixed combinations of a prostaglandin analogue and a beta-blocker are considered, concern has been raised about limited advantage in terms of IOP-lowering effect (about 1 mmHg) over the prostaglandin given alone, as reported in phase III trials. The trial by Palmberg et al. (1368) is a twelve-week comparison of the latanoprost-timolol fixed combination (LTFC) with its components, which was designed in order to solve some controversies in terms of efficacy results of the LTFC among published clinical trials. Firstly, good responders to timolol were selected, with inclusion IOP at baseline ranging from 26 to 36 mmHg; secondly, the vast majority of patients had glaucoma, potentially being better responders to LTFC than patients with ocular hypertension, and thirdly, LTFC was administered in the evening. However, despite the differences in the study design, the results of the Palmberg trial were very similar to what reported in the previous phase III studies, with an average difference between the effect of LTFC and latanoprost of about 1 mmHg both at six and twelve weeks. The difference in the IOP lowering effect between LTFC and timolol (curiously given only once daily in the morning) was about 2-2.5 mmHg. The trial was designed in order to detect a difference of 1.5 mmHg between the study drugs, and resulted to be overpowered as differences of 0.81 mmHg (LTFC vs latanoprost, week 12 at 8 am) reached statistical significance. It seems that no matter what is the study design, phase III trials on IOP-lowering efficacy of LTFC provide comparable results, often in disagreement with the findings of other smaller published investigations. Reasons for conflicting results among studies should be searched elsewhere.

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