The FDA has just approved a new agent for male erectile dysfunction - Stendra (avanafil).
This medication is in the same class as Viagra (sildenafil), Levitra (vardenafil), and Cialis (tadalafil) - phosphodiesterase type 5 inhibitors, or PDE-5 inhibitors.
How does this new agent compare to the existing drugs? Avanafil's reported time to maximal blood level or Tmax is 0.593 hours compared to 1, 0.7, and 2.0 hours for sildenafil, vardenafil, and tadalafil respectively. The reported half-life is 1.19 hours compared to 3-5, 4-5, and 17.5 hours for the other three respectively.
Reference: Drug Des Devel Ther. 2011;5:435-443
Based on this pharmacokinetic data, avanafil should work faster then be more quickly eliminated from the body compared to the other currently available drugs. It's targeting the end of the market where people want a fast onset of action and only have the medication in their system for the least amount of time.
Tadalafil targets the other end of the market where a man can take a daily formulation (2.5 mg or 5 mg) to be ready at any time or an as needed formulation (10 or 20 mg) where he can be ready for up to 36 hours.
It's too early to say what the differential impact will be between all of these drugs clinically. In the end, as some of the older drugs come off patent in a few years and the US market is flooded with generics, the relative cost of each agent will likely be a significant driving factor as to what oral agent patients choose.
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