ERG evaluation of daily, high-dose sildenafil usage

Purpose Sildenafil can cause transient, mild ERG changes in healthy individuals taking large single doses. Although the drug was originally intended for intermittent use in erectile dysfunction, it has now been approved for chronic use in subjects with pulmonary arterial hypertension (PAH). The purpose of our study is to investigate possible ERG changes in subjects using large doses of sildenafil on a chronic daily basis. Methods We examined five subjects with PAH taking sildenafil daily for 1-4 years. Full-field electroretinogram (ERG), multifocal ERG (mfERG), and color testing were performed. Three of the subjects returned on a later date for challenge off and on the medication. Results On chronic daily sildenafil, color vision testing was normal, and ERG and mfERG amplitudes were normal; however, cone implicit times on drug were modestly lengthened. There were no consistent full-field ERG changes when off the drug, but the mfERG showed a small amplitude increase and implicit time decrease, which returned 1 h after re-dosing. Conclusion There was a modest lengthening of cone implicit time on chronic daily doses of sildenafil and a hint that some of these changes may be reversible in the short term. It does not appear that chronic sildenafil usage at these dosage levels is seriously toxic or threatening to vision.