sildenafil-citrate and Color-Vision-Defects

Sildenafil citrate improves erectile function in men with erectile dysfunction (ED) by selectively inhibiting cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5), which is present in all vascular tissue. Sildenafil also has a weaker inhibitory action on PDE6, located in the rod and cone photoreceptors. Modest, transient visual symptoms, typically blue tinge to vision, increased brightness of lights, and blurry vision, have been reported with sildenafil use and occur more frequently at higher doses. Visual function studies in healthy subjects and in patients with eye disease suggest that sildenafil does not affect visual acuity, visual fields, and contrast sensitivity. Transient, mild impairment of color discrimination can occur around the time of peak plasma levels. Spontaneous postmarketing reports of visual adverse events, including nonarteritic anterior ischemic optic neuropathy (NAION), have been reported during the 7 years that sildenafil has been prescribed to more than 27 million men worldwide. However, because men with ED frequently have vascular risk factors that may also put them at increased risk for NAION, a causal relationship is difficult to establish. No consistent pattern has emerged to suggest any long-term effect of sildenafil on the retina or other structures of the eye or on the ocular circulation.

Topics: Color Vision Defects; Controlled Clinical Trials as Topic; Erectile Dysfunction; Humans; Male; Optic Neuropathy, Ischemic; Phosphodiesterase Inhibitors; Piperazines; Purines; Sildenafil Citrate; Sulfones; Vasodilator Agents; Vision Disorders; Visual Acuity; Visual Fields

Topics: Color Perception Tests; Color Vision; Color Vision Defects; Erectile Dysfunction; Humans; Male; Middle Aged; Phosphodiesterase 5 Inhibitors; Sildenafil Citrate; Tadalafil

Topics: Color Vision Defects; Fluorescein Angiography; Humans; Male; Middle Aged; Phosphodiesterase 5 Inhibitors; Piperazines; Purines; Scotoma; Sildenafil Citrate; Sulfones; Tomography, Optical Coherence; Visual Field Tests; Visual Fields

To date, sildenafil citrate (Viagra) gives every evidence of being a safe drug for the eye despite a series of expressed concerns. A review of how its ocular safety profile has been identified offers insights into the strengths and weaknesses of present systems and resources for judging the ocular safety of Viagra or, for that matter, of any new drug. Such insights include: The great value of careful, informed assessment of preclinical information gleaned from laboratory experiments. By and large, such assessments point the way toward appropriate clinical evaluation. For Viagra, early in its development it was noted that besides exerting a major inhibitory effect on the intended target, the vascular-associated enzyme phosphodiesterase 5 (PDE5), the drug also exerts a lesser but definite inhibitory effect on the closely related PDE6, located in the retina. For this reason, preclinical evaluation of the drug included electroretinography plus postmortem histology. In addition, an extended eye examination was incorporated into clinical protocols. The often chaotic but invaluable information stream that becomes available once marketing approval has been gained and large populations begin to use a drug. False alarms, misattribution, and erroneous information are the order of the day. Nevertheless, as information accumulates, patterns of response clarify and the true nature of special susceptibility for subpopulations, if any, becomes apparent. A role for the astute clinician remains: Subtle changes or unusual risks for subpopulations can be missed entirely for long periods of time. A manifest need for improvement in evaluation of postmarketing side-effects. This need has led to the establishment of a new discipline: pharmacoepidemiology. In ophthalmology, the National Registry of Drug Induced Ocular Side-Effects maintains a constant and invaluable surveillance. Examples are supplied to illustrate each of these major points: Our presentation will include data gleaned from clinical trials plus postmarketing information on the incidence, duration, and type of color vision defects observed at different doses of Viagra.

Topics: 3',5'-Cyclic-GMP Phosphodiesterases; Animals; Clinical Trials as Topic; Color Perception; Color Vision Defects; Electroretinography; Humans; Intraocular Pressure; Male; Phosphodiesterase Inhibitors; Piperazines; Purines; Retina; Safety; Sildenafil Citrate; Sulfones; Visual Acuity; Visual Fields