The influence of diclofenac ophthalmic solution on the intraocular pressure-lowering effect of topical 0.5% timolol and 0.005% latanoprost in primary open-angle glaucoma patients

The aim of this randomized, prospective, masked clinical study has been to verify the influence of a non-steroidal anti-inflammatory drug ophthalmic solution on intraocular pressure reduction induced by 0.5% timolol and 0.005% latanoprost eyedrops, in patients affected by primary open-angle glaucoma. Thirty-two glaucomatous patients, compensated with 0.5% timolol, were randomized into two study groups (A and B). Timolol was continued for the first two weeks in all subjects. On the 15th day, in both groups timolol was replaced by latanoprost, and this regimen lasted up to the end of the follow-up (8 weeks). At the beginning of the 2nd week of the study, group A additionally started a 5-week therapy with topical 0.1% diclofenac; during the same period, group B received placebo eyedrops with identical modalities. Intraocular pressure was recorded at 7-day intervals during the first seven weeks and at the 10th week. Non-steroidal anti-inflammatory drug and placebo did not modify the effect of timolol on intraocular pressure. In both groups, latanoprost induced a significant decrease in intraocular pressure. Diclofenac-treated patients exhibited a marked fall in intraocular pressure (p < 0.01), whereas in placebo-treated patients, this diminution was less noticeable (p < 0.05). After diclofenac withdrawal, in group A intraocular pressure significantly increased (p < 0.01), remaining approximately at the same level up to the end of the study. In group B, at the same checks no significant variations in intraocular pressure occurred. In primary open-angle glaucoma patients, diclofenac significantly enhances the hypotensive effect of latanoprost, without influence on timolol efficacy. Because non-steroidal anti-inflammatory drugs are widely employed in medical practice, supplementary ophthalmologic checks should be scheduled during the co-administration of these compounds and prostaglandin analogues