Udenafil is the fourth in a class of drugs targeting the inhibition of the enzyme
phosphodiesterase 5 (PDE5) for the treatment of erectile dysfunction. Inhibition of
PDE5 results in the increase in endogenous cyclic guanosine monophosphate
(cGMP) concentrations in the penile corpus cavernosum. cGMP induces smooth
muscle cell relaxation and subsequent increased blood flow leading to a sustainable
erection. Udenafil is a potent antagonist of human PDE5 with an IC50 of 8.25nM
and a comparable selectivity profile as sildenafil for the other PDEs. Unlike tadalafil,
it does not inhibit PDE11, which has been implicated in myalgia and
testicular toxicity. Furthermore, udenafil produced up to a 91% vaginal
penetration success rate and up to a 67% intercourse completion rate compared to a
29% completion rate by placebo. Overall patient satisfaction, measured by a
standard global assessment question, was 86% compared to only 26% in the placebo
group. The most frequently recorded adverse events were mild-to-moderate
facial flushing and headache.
