High biochemical selectivity of tadalafil, silde nafil and vardenafil for human phosphodiesterase 5A1 (PDE5) over PDE11A4 suggests the absence of PDE11A4 cross-reaction in patients - Weeks, JL; Zoraghi, R; Beasley, A; Sekhar, KR; Francis, SH; Corbin, JD (Int J Impot Res., 2005)