Sildenafil- and tadalafil-associated optic neuropathy: implications for men after prostate cancer treatment

Abstract

The phosphodiesterase 5 (PDE5)-selective inhibitors sildenafil (Viagra), tadalafil (Cialis), and vardenafil (Levitra) are frequently prescribed for treatment of erectile dysfunction (ED). 1 These medications have implications for men with prostate cancer who undergo treatment with radical prostatectomy or radiation therapy (brachytherapy or external beam radiation), as these treatments are associated with an increased risk for ED. Instances of nonarteritic ischemic optic neuropathy (NAION) and permanent vision loss following ingestion of PDE5-selective inhibitors have been reported.2 – 4 Investigators affiliated with the Research on Adverse Drug Events and Reports (RADAR), an established pharmacovigilance program, reviewed the literature as well as US Food and Drug Administration (FDA) reports to determine the frequency and clinical characteristics of PDE5selective inhibitor-associated NAION and permanent vision loss in men with ED. Reports and associated toxicities We reviewed case descriptions of PDE5-selective inhibitor-associated optic neuropathy events reported to the FDA between 1998 and 2004 or in the peer-reviewed literature between 1998 and 2005. Thirty-nine cases of optic neuropathy in sildenafil- or tadalafil-treated patients were identified as case reports (n = 18) or in FDA databases (n = 21). Affected men were similar in age (median, 62 years), and 90% of the cases were reported among men who had ingested PDE5-selective inhibitors and suffered permanent vision loss. Importantly, the quality of the case reports in the FDA database is suboptimal given that they often lack important information on duration of PDE5-selective inhibitor use, time since ingestion of the most recent dose, identification of affected eye, fundoscopic examination findings, and response to de-challenge. A plausible explanation as to cause-and-effect relative to PDE5-selective inhibitor therapy and NAION does not exist.