A drug’s half-life is the amount of time required for the concentration of the medication in your body to fall to half of its peak. For example, a normal 50mg dose of sildenafil (Viagra) will be reduced to the potency of approximately 25mg after one half-life has passed.
The half-life of a medication determines how long it will remain active in the body. Generally, ED drugs still provide some effects after one half-life and gradually become less effective as they’re eliminated from the body and excreted.
After two to three half-lives have passed, the medication will be completely ineffective and won’t provide any noticeable effects.
Below, we’ve listed both the half-lives and duration of action for all four of the most common ED drugs:
Sildenafil (Viagra), has a half-life of four hours and remains active in the body as an effective erectile dysfunction treatment for three to five hours after it’s consumed. After five hours have passed, sildenafil usually won’t provide any noticeable benefits.
Tadalafil (Cialis), has a half-life of 17.5 hours and remains active in the body as an effective erectile dysfunction treatment for up to 36 hours after it’s consumed. This has earned it a reputation as a “weekend pill” for treating ED.
Vardenafil (Levitra), has a half-life of four to five hours and remains active in the body for up to six hours after it’s consumed. This gives it a slightly longer period of an effect than sildenafil.
Avanafil (Stendra), has a half-life of five hours and remains active in the body for up to six hours after it’s consumed. This gives it a similar period of an effect than vardenafil and a slightly longer half-life than sildenafil.
As you can see, tadalafil is by far the longest-lasting of the four ED medications currently on the market.
Because of this, tadalafil is usually the preferred option for men who want to treat ED for several days at once without needing to take several tablets of their ED medication. Shorter-acting drugs, such as sildenafil, vardenafil, and avanafil, are generally preferred for incidental use. Tadalafil also has the added benefit of treating benign prostatic hyperplasia (BPH). Of course, using tadalafil to treat either erectile dysfunction or BPH should always be discussed with your primary care physician.