Question

A drug has a half-life of 8 hours and oral bioavailability of

40%. if 200 mg of the drug is administered orally, how much drug
will remain in systemic circulation after 24 hours?

Answer 1

Using the half-life of 8 hours and an oral bioavailability of 40%, 10 mg of the 200 mg administered drug will remain in systemic circulation after 24 hours.

Step-by-step explanation:

To calculate how much of a drug will remain in systemic circulation after a certain period of time, we can use the drug's half-life and its oral bioavailability. In this case, the drug has a half-life of 8 hours, and its bioavailability is 40%. If 200 mg of the drug is administered orally, first we need to calculate the amount that enters the systemic circulation, which would be 200 mg × 40% = 80 mg.

Next, we calculate how many half-lives have passed after 24 hours. Since 24 hours divided by 8 hours per half-life equals 3, there are three half-lives. After each half-life, the amount of drug is reduced by half, so the calculations would be as follows:

1. After the first half-life (8 hours), 80 mg / 2 = 40 mg remaining.
2. After the second half-life (16 hours), 40 mg / 2 = 20 mg remaining.
3. After the third half-life (24 hours), 20 mg / 2 = 10 mg remaining.

Therefore, after 24 hours, 10 mg of the drug will remain in systemic circulation.