# If a Tadalafil 10 mg/tab has a typical half life of 17.5 hours, how long will it take until the blood concentration of this dosage falls to 25% of its initial strength?

##### 1 Answer

Feb 10, 2017

35 hours.

#### Explanation:

A half-life is the amount of time it takes for half of a material to decay or decompose. So, after one half-life you have 50% of the initial material remaining.

**However!**

**Now 50% is the new 100%!**

So in the next half-life we are going to lose **only half** of the remaining material.

Half of 50% is 25%.

So after two half-lives the amount of Taldalafil will be 25% of the initial amount.