Effect of Aspirin on Photodynamic Therapy A new study published in the current edition of the journal Retina finds that patients taking aspirin had worse visual outcomes following photodynamic therapy (PDT).

PDT with verteporfin is used for treatment of choroidal neovascularization in several conditions, including age-related macular degeneration. Platelet aggregation is one of the mechanisms by which PDT is thought to work. This study sought to examine the hypothesis that systemic use of aspirin, an inhibitor of platelet aggregation, affects the efficacy of PDT.

A retrospective review was conducted of data for patients treated with PDT at one institution between 2001 and 2004. End points included total number of PDT treatments, mean time between PDT treatments, change in visual acuity from baseline to 3 months after last PDT treatment, and concurrent or subsequent treatments other than PDT.

Investigators reviewed the records of 244 eyes of 222 patients undergoing PDT at their institution between 2001 and 2004. There were 102 eyes from 92 patients were included in the aspirin taking group. Aspirin takers received an average of 3.11 PDT treatments compared with 2.39 PDT treatments for nonaspirin takers. Decrease in visual acuity was greater for aspirin takers, with a loss of >=3 lines seen in 58% of aspirin takers compared with 35% of nonaspirin takers. These differences remained statistically significant after controlling for patient age, lesion type, and lesion size.

The researchers conclude that patients taking aspirin required more PDT treatments and had worse visual outcomes than patients not taking aspirin, possibly due to aspirin's ability to inhibit platelet aggregation and thereby diminish the efficacy of PDT.

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Retina. 28(5):711-716, May 2008.