PDE5A and erectile dysfunction: Tadalafilis the active ingredient in Cialis, which is manufactured by Eli Lilly and prescribed forerectile dysfunction.14Vardenafil, the active ingredient in the prescription drug Levitra produced by BayerPharmaceuticals for erectile dysfunction, was detected in 5 products over the 10-yearperiod.15 Sildenafil,tadalafil, and vardenafil are all phosphodiesterase-5 (PDE5) inhibitors and affect the samepathway in order to treat erectile dysfunction.16 Other PDE5 inhibitors, including PDE5 inhibitor analogues, were alsodetected in 27 of 353 adulterated sexual enhancement products (7.6%).