It's not a penis drug. It's a blood-flow drug.
Sildenafil is a potent and selective inhibitor of cGMP specific phosphodiesterase type 5 (PDE5)
PDE-5 is primarily distributed within the arterial wall smooth muscle of the lungs and penis, sildenafil acts selectively in both these areas without inducing vasodilation in other areas of the body
Catlin said he even wrote a letter several years ago to then-WADA chairman Dick Pound, notifying him that Viagra might be a doping agent.The e-mail got bounced back by Pound's offensive-content filter, which thought it was spam.
It should be pretty easy to spot any racing cyclist one who's taken Viagra.They'll be the ones in baggy shorts.