Figure 1

Graphs depicting plasma concentrations of sildenafil and N -desmethyl sildenafil. Sildenafil (open diamonds) and its major, partially active metabolite N-desmethyl sildenafil (circles) after enteral (open symbols) and sublingual administration (closed symbols) to two infants. The dotted lines are extrapolated assuming that plasma concentrations during steady state are identical at different dosing intervals.