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Editors Selection IGR 14-4
Medical Treatment: Non-responders to latanoprost
Comment by George Lambrou on:
13892 An evaluation of the rate of nonresponders to latanoprost therapy, Rossetti L; Gandolfi S; Traverso C et al., Journal of Glaucoma, 2006; 15: 238-243
Quick, and without looking it up: How much will latanoprost lower the IOP of your prostaglandin-virgin POAG/OHT patient and what are the chances it will do so? Most ophthalmologist will readily (and rightly) answer '30% on average' to the first question, but you are likely to collect a diverse set of answers to the second one. Published studies based on differing patient groups, criteria for non-response and treatment durations quote nonresponder (or 'low-responder') rates from as low as 2% to as high as 50%.
Rossetti et al. (526) have designed a prospective multicentric study, enrolling 340 patients across 10 Italian teaching hospitals, to evaluate the prevalence of non-responders to 30-day latanoprost monotherapy among patients never exposed previously to prostaglandins; the non-responders were subsequently enrolled in a three-arm cross-over trial to investigate their response to timolol, brimonidine and pilocarpine.
Non-responders to latanoprost were found in only 4.1%
The study, supported in part by a grant from Pfizer, found an average IOP reduction of 29.9 &plm; 4.2%, consistent with the literature. The proportion of non-responders, defined as patients with an IOP reduction lower than 15% was very low: 14 patients out of 340 (4.1%), while the proportion of 'high responders', defined as patients with an IOP reduction higher than 30%, reached 41.2% (140 patients out of 340). The low rate of nonresponders was unexpected even for the authors, who had designed the subsequent cross-over trial assuming a 10% non-response rate. Thus, the cross-over trial, enrolling only 14 patients, was underpowered to be conclusive. The effects of brimonidine and timolol seemed roughly equivalent (with only brimonidine reaching statistical significance) while pilocarpine was even less effective.
As the authors acknowledge, the study has a number of limitations: its design was non-randomized, non-controlled, open-label, single-arm, which may have given rise to bias. Second, the short follow-up with only one time-point beyond baseline (at one month) did not permit to evaluate the proportion of long-term nonresponders. Still, and although it is unlikely to affect individual clinical practice, the study sheds some new light on the question of non-response to prostaglandins, principally of interest to pharmacoeconomists, health authorities and the pharmaceutical industry
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