A steady state plasma concentration is achieved in how many hours, if half life of drug is 40 hrs. ?

Ans. is 'c' i.e., 200 hrs For all practical purposes, after 5 t1/2 the amount of drug in the body will be constant and the plasma concentration will be at a plateau. Thus for a drug with T1/2 40 hrs to reach the steady state plasma concentration 5 t1/2s will be required. i. e. 5 X 40 hrs = 200 hrs.