This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General Pharmacology, Subject name: Pharmacology
With IV infusion, a drug reaches 90% of its final steady state in 10 hours. The elimination half-life of the drug must be approximately 
Select and explain. 
A. 1 h, B. 2 h, C. 3 h, D. 6 h
C: 3 h
Answer: C: 3 h 
Explanation: Time to reach 90% of final steady-state plasma levels is given by: 3.3xhalflife.Because it takes 10 h to reach 90% steady state, thenHalflife=3.310 =3hTo achieve "clinical" steady state usually takes approximately 5xhalflife.