Figure 1.

Advantages and disadvantages of plasma concentration curves of PDE5is taken on demand. (A) Schematic diagram of examples of plasma concentration curves that might be obtained with different formulations (A, A1, B, C, and D curves of PDE5is). (B) Magnification of the curves depicted in A during the first hour. The time needed to reach the minimum effective concentration is T_onset, the maximum drug plasma concentration is C_max, and the time at which C_max is reached is T_max (indicated only for the specified formulations). Desired and unwanted effects of PDE5is are depicted. Within the therapeutic windows, lower and higher PDE5i concentrations were considered to give an EHGS grade 3 erection and grade 4 erection (fully rigid erection), respectively. Figure shows the clinical effects of a PDE5i depend on dose, half‐life, and formulation of a drug, determining different plasma concentration curves. Both A and A1 reach a plasma concentration sufficiently high to give a fully rigid erection (EHGS grade 4) after 5–10 min (despite the different T_max), and their concentrations are sufficiently high for long enough to allow satisfactory sexual activity. The plasma concentrations of B and C, derived from different doses of the same drug formulations, are both suboptimal for adverse effects or efficacy, respectively. The plasma concentration of formulation D is suboptimal for duration of the wanted effect.