1. Describe MOA for PDEi’s in context of pathophysiology of ED?

2. SAR of PDEi’s. Describe the effect of functional groups highlighted in colors ( red and blue) on activity of PDEi shown in figure below.

3. Why tadalafil half-life ( 18 hrs) is much longer than sildenafil (6 hrs)?

4. Are the PDEi’s lipophilic or hydrophilic? Explain the effect of cLogP. What is the one implication of cLogP from the patients education point of view?

5. How PDEi’s used for ED differ from Alprostadil?