Medication A has a half-life of 3 hours. If the nurse administers a single dose of 400 mg of medication A, how much will excrete from the patient’s body after 12 hours?

Choice A Reason:

To determine how much of the medication remains in the body after a certain period, we need to understand the concept of half-life. The half-life of a medication is the time it takes for the concentration of the drug in the bloodstream to reduce by half. For Medication A, the half-life is 3 hours. After 12 hours, which is four half-lives, the amount of medication remaining can be calculated step by step.

Choice B Reason:

Let’s break down the calculation. Initially, the patient receives 400 mg of Medication A. After the first half-life (3 hours), the amount of medication remaining is 400 mg ÷ 2 = 200 mg. After the second half-life (6 hours), the amount remaining is 200 mg ÷ 2 = 100 mg. After the third half-life (9 hours), the amount remaining is 100 mg ÷ 2 = 50 mg. Finally, after the fourth half-life (12 hours), the amount remaining is 50 mg ÷ 2 = 25 mg. Therefore, 375 mg is not a correct answer.

Choice C Reason:

Similarly, 150 mg is not correct. As shown in the detailed calculation, the amount of medication decreases by half every 3 hours. After 12 hours, the remaining amount is 25 mg, not 150 mg. This choice does not align with the half-life calculation.

Choice D Reason:

This is the correct answer. The step-by-step calculation shows that after 12 hours, which is equivalent to four half-lives, the amount of Medication A remaining in the patient’s body is 25 mg. This demonstrates the principle of half-life and how the concentration of a drug decreases over time.

Choice A Reason:

The statement that the medication will be completely out of the patient’s body after three days is incorrect. The half-life of a drug indicates the time it takes for the concentration of the drug in the body to reduce by half. After one half-life (one day), 50% of the drug remains. After two half-lives (two days), 25% remains. After three half-lives (three days), 12.5% remains. Therefore, some amount of the drug will still be present in the body after three days.

Choice B Reason:

To calculate the amount of medication remaining after three days, we use the half-life formula. Starting with 10 mg, after one day (one half-life), 5 mg remains. After two days (two half-lives), 2.5 mg remains. After three days (three half-lives), 1.25 mg remains. This calculation shows that 1.25 mg of the medication will still be in the patient’s body after three days.

Choice C Reason:

The choice of 5 mg is incorrect because it represents the amount of medication remaining after one half-life (one day), not three half-lives. After one day, 50% of the initial dose remains, which is 5 mg. However, the question asks for the amount remaining after three days.

Choice D Reason:

The choice of 1 mg is also incorrect. After three half-lives, the amount of medication remaining is 12.5% of the initial dose. For an initial dose of 10 mg, this would be 1.25 mg, not 1 mg. The calculation must accurately reflect the reduction by half for each half-life period.