Fig. 3
Plot of observed plasma sildenafil concentrations vs time after sildenafil dosing. Legend: Plasma sildenafil concentrations (open circles), sildenafil doses of 1 mg (left), 5 mg (middle), and 20 mg (right). Median (solid line) and 90% prediction intervals (dashed lines) from simulations are overlaid. Tick marks on the horizontal time axis indicate concentration measures below the limit of quantification. The shaded area shows the concentration range between 3 ng/mL and 20 ng/mL, which are the average sildenafil plasma concentrations required to achieve 50% effect (EC50) and 90% effect (EC90) on PVRI, respectively. TID = 3 times daily