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C. I. Zoumalan, R. T. Zamanian, R. L. Doyle, M. F. Marmor; ERG Changes in Patients Chronically Using Sildenafil for Pulmonary Arterial Hypertension. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3809.
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Sildenafil can cause transient, mild electroretinogram (ERG) changes in healthy individuals taking large single doses (e.g. 100-200 mg). Although the drug was originally intended for intermittent use in erectile dysfunction (ED), it has now been approved for chronic use in patients with pulmonary arterial hypertension (PAH). Though the recommended dose for PAH is 20 mg 3 times a day, many patients are given higher doses (e.g. 50-75 mg 3 to 4 times a day) depending on the severity of their disease. We sought to investigate possible ERG changes in patients using large doses of sildenafil on a chronic basis.
We evaluated four female patients (age 40 +/- 5.2 years) who had no prior retinal disease. All had been using sildenafil for management of PAH, at doses of 225 +/- 50 mg/day, for 2-4 years. Evaluation included best corrected visual acuity, color vision (Farnsworth Panel D-15 test), full-field ERG (UTAS E-2000 system) and multifocal ERG (mfERG) (VERIS system). Two patients also had mfERG testing while off medication overnight for 9-12 hours (longer intervals being difficult).
All patients had visual acuity of 20/20 in both eyes, and normal color vision other than some minor confusions on the desaturated Panel D-15 test. Full-field ERGs showed normal dark-adapted responses and normal cone amplitudes in 3 of 4 subjects. However, all 4 showed borderline or clearly elevated cone implicit time to both single flash and 30 Hz photopic stimulation. The mfERG responses were of normal amplitude, but clearly delayed in 3 of 4 subjects. The two patients who transiently stopped medication showed a small increase in mfERG amplitude and a small decrease in implicit time (average 1 ms) that returned to baseline 1 hour after taking the morning dose.
Our results show a lengthening of cone implicit time on chronic, daily doses of sildenafil that is comparable to effects reported with larger (100-200 mg), single doses. There is a suggestion that some of these changes may be reversible in the short term (i.e. represent a short term pharmacologic effect), but further studies will be needed to assess whether there are any permanent ERG effects. It does not appear, however, that chronic sildenafil usage at these dosage levels is seriously toxic or threatening to vision.
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