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The nurse gives 800 mg of a drug that has a half-life of 8 hours. How much drug will be left in the body in 24 hours if no additional drug is given?

A.

None

B.

50 mg

C.

100 mg

D.

200 mg

Answer and Explanation

The Correct Answer is C

A. The statement that no drug remains is incorrect. A drug with a half-life of 8 hours will not be completely eliminated in 24 hours, as it follows a predictable pattern of reduction. 

B. A reduction to 50 mg would require additional half-life intervals beyond 24 hours. The drug concentration decreases by half every 8 hours, meaning it would take more than 24 hours to reach this level. 

C. The correct calculation follows the half-life principle: 

   - At 8 hours: 800 mg → 400 mg 

   - At 16 hours: 400 mg → 200 mg 

   - At 24 hours: 200 mg → 100 mg 

   Therefore, 100 mg of the drug remains after 24 hours. 

D. While 200 mg is a step in the process, it represents the amount remaining after only 16 hours, not the full 24-hour period. 


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Related Questions

Correct Answer is C

Explanation

a) Complete blood counts (CBC) are useful for monitoring infection, anemia, or bone marrow suppression, but they are not the primary concern for azithromycin and acetaminophen toxicity.

b) Electrolytes are important for general health but are not directly related to the major side effects of these drugs.

c) Liver enzymes (AST, ALT) should be monitored because both azithromycin and acetaminophen can cause hepatotoxicity, especially at high doses. Acetaminophen overdose is a known cause of liver failure.

d) Urinalysis may be helpful in assessing kidney function, but it is not the primary focus when monitoring for drug-induced liver toxicity.

Correct Answer is C

Explanation

A. The statement that no drug remains is incorrect. A drug with a half-life of 8 hours will not be completely eliminated in 24 hours, as it follows a predictable pattern of reduction.

B. A reduction to 50 mg would require additional half-life intervals beyond 24 hours. The drug concentration decreases by half every 8 hours, meaning it would take more than 24 hours to reach this level.

C. The correct calculation follows the half-life principle:

- At 8 hours: 800 mg → 400 mg

- At 16 hours: 400 mg → 200 mg

- At 24 hours: 200 mg → 100 mg

Therefore, 100 mg of the drug remains after 24 hours.

D. While 200 mg is a step in the process, it represents the amount remaining after only 16 hours, not the full 24-hour period.

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