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Regular users of common medications for erectile dysfunction (ED) are at a higher risk for ocular adverse events, according to a large cohort study.

Among over 200,000 men using phosphodiesterase type 5 inhibitors (PDE5Is), the adjusted incidence rate ratio (IRR) for the composite endpoint of serous retinal detachment (SRD), retinal vascular occlusion (RVO), and ischemic optic neuropathy (ION) was 1.85 (95% CI 1.41-2.42), reported Mahyar Etminan, PharmD, MSc, of the University of British Columbia in Vancouver, and colleagues in .

When analyzed by individual outcome, the adjusted IRRs were:

• 2.58 (95% CI 1.55-4.30) for SRD
• 1.44 (95% CI 0.98-2.12) for RVO
• 2.02 (95% CI 1.14-3.58) for ION

These ocular adverse events have previously been reported with use of PDE5Is, but mostly in the form of anecdotal studies that produced inexact estimates for these risks. "Results of this study suggest that individuals who regularly use PDE5Is should be cognizant of ocular adverse events associated with these drugs and alert their physicians if they experience any visual deficits," the authors wrote.

In an , Brian L. VanderBeek, MD, MPH, MSCE, of the University of Pennsylvania in Philadelphia, and Maureen G. Maguire, PhD, of the JAEB Center for Health Research in Tampa, Florida, noted that "this study also had a weakness that has plagued previous inquiries into the ocular adverse events related to PDE5I use."

Many of the risk factors for the indications for using PDE5Is -- hypertension, diabetes, and coronary artery disease -- are also risk factors for SRD, RVO, and ION, they added, and the prevalence of these risk factors in this study was substantially higher among cases versus controls.

When Etminan and colleagues restricted the primary analysis to cases without hypertension, diabetes, or coronary artery disease, the IRR remained high, at 2.12 (95% CI 1.34-3.43).

However, "residual confounding could have occurred owing to a lack of adjustment for other common risk factors between erectile dysfunction and the adverse events," VanderBeek and Maguire wrote. Furthermore, "residual confounding frequently yields overestimation of the risk ratios."

While the study's findings suggest that PDE5I use may be associated with serious ocular adverse events, causality can't be proved by using only observational data, they concluded. "Future studies that reduce residual confounding may bolster the confidence in conclusions regarding PDE5I use and these adverse events."

Data for this study came from the PharMetrics Plus database from January 2006 through December 2020. The study cohort included 213,033 users of PDE5Is, including sildenafil (Viagra, Revatio), tadalafil (Cialis), vardenafil (Levitra), and avanafil (Stendra), who did not use any of the drugs in the year before study entry. The nested case-control analysis included 278 cases of SRD, 628 of RVO, and 240 of ION, as well as 4,584 controls. Mean age in both the case and control groups was 64.6 years.

Risk factors were more common in case patients versus controls: hypertension (24.6% vs 8.9%), diabetes (38.1% vs 26.1%), coronary artery disease (36.1% vs 24.0%), and sleep apnea (15.5% vs 10.6%).

An analysis comparing the risk between men taking five or more PDE5I prescriptions compared with those taking fewer than five prescriptions showed a dose-response association with ocular adverse events (IRR 2.90, 95% CI 1.15-3.81 vs IRR 1.74, 95% CI 1.10-6.77).

When analyzed by individual outcome in this analysis, the adjusted IRRs were:

• 1.90 (95% CI 1.41-2.55) vs 1.73 (95% CI 1.14-2.64) for SRD
• 2.39 (95% CI 1.38-4.14) vs 3.30 (95% CI 1.48-7.38) for RVO
• 1.55 (95% CI 1.00-2.40) vs 1.25 (95% CI 0.70-2.21) for ION

Etminan and colleagues acknowledged that they only had data on drug dispensation and not on actual consumption, which was a study limitation.

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