Non-arteritic anterior ischemic optic neuropathy (NAION) and phosphodiesterase type-5 inhibitors

To determine whether a causative relationship exists between non-arteritic anterior ischemic optic neuropathy (NAION) and the use of phosphodiesterase-5 (PDE-5) inhibitors for the treatment of erectile dysfunction.

A comprehensive review of the literature was performed to identify the contemporary understanding of NAION pathophysiology, epidemiology, and occurrence in men using the oral PDE-5 inhibitors sildenafil (Viagra, Pfizer), vardenafil (Levitra, Bayer AG), and tadalafil (Cialis, Lilly-ICOS LLC) for the treatment of erectile dysfunction.

NAION is the second most common acquired optic neuropathy in men aged 50 years and older. Risk factors for NAION, cardiovascular disease, and erectile dysfunction are shared and include age, dyslipidemia, diabetes, hypertension, and cigarette smoking. To date, less than 50 cases of NAION associated with PDE-5 use have been reported to the United State's Food and Drug Administration (FDA) and five Canadian cases alerted to Health Canada. Given the large number of men safely using these agents and a limited number of events, it is not possible to determine whether NAION is directly linked to the use of PDE-5 inhibitors, underlying cardiovascular risk factors, ocular anatomical defects, a combination of these variables, or as yet unidentified factors.

PDE-5 inhibitors have gained widespread use for the treatment of erectile dysfunction due to their safety, efficacy, and ease of use. Their role in the pathogenesis of NAION remains controversial. Reasonable and informed consent regarding the possible but low risk of NAION with the use of sildenafil, vardenafil and tadalafil is recommended. Loss or decreased vision, whether painful or painless, demands urgent patient assessment and immediate cessation of PDE-5 inhibitor use.