This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pharmacokinetics, Subject name: Pharmacology
Steady state concentration of a drug is achieved in:- 
Select and explain. 
A. 2-3 half lives, B. 3-4 half lives, C. 4-5 half lives, D. 5-6 half lives
C: 4-5 half lives
Answer: C: 4-5 half lives 
Explanation: STEADY STATE - If fixed dose of a drug is administered after regular intervals, its plasma concentration stas increasing. - However, as plasma concentration rises, rate of elimination also stas increasing. When rate of administration becomes equal to rate of elimination, plasma concentration stabilizes. This is called steady state. - Time to reach steady state depends on t 1/2 . It takes approximately 4-5 half lives. - Steady state plasma concentration achieved depends on dose rate. - Variation between peak and trough concentration at steady state depends on dosing interval. However, average steady state plasma concentration remains same irrespective of dosing interval provided dose rate remains same.