Vardenafil (Levitra) received FDA approval in August, 2003. It can be taken in 2.5, 5, 10, and 20 mg doses. While higher doses may improve its efficay, the risk of side effects also increases with dose as well. Vardenafil has a rapid onset of action, between 30 and 45 minutes. This is slightly faster than the other two agents. While laboratory testing has shown that it is has a greater ability to bind to the PDE5 enzyme than the other two drugs, a variety of factors related to its absorption into the blood stream counteract this. As a result, it is no more effective than the other two medications. Vardenafil has a similar side effect profile to sildenafil, and can cause headaches, visual disturbances, dizziness, and headaches. It should never be taken in anyone taking nitrates, and also should never be taken by someone taking any prostate medications such as terazosin (Hytrin), doxazosin (Cardura), tamsulosin (Flomax), or alfuzosin (Uroxatral).
Tadalafil (Cialis) is the newest medication approved for male ED. While it has a slower onset of action, which can occur at 45 minutes to 2 hours after taking the medication, it has the distinction of being effective for up to 36 hours. This may improve the spontaneity of sexual activity for some couples. It also however may increase the amount of time during which a side effect may be present. Its interaction with a different type of PDE enzyme in the body may cause back and muscle pain in some people, which may last for the 36 hours in which the medication is present in the blood stream.
