Outcomes of Other Medicines on VIAGRA Sildenafil metabolism is principally mediated by CYP3A4 (significant route) and CYP2C9 (small route). Consequently, inhibitors of such isoenzymes may well lower sildenafil clearance and inducers of these isoenzymes may enhance sildenafil clearance.Sildenafil can reduce blood stream to the optic nerve of the eye