<prompt> Young child weighing 20 kg was given a drug in the dose lOOmgkg body weight. The plasma concentration of the drug is 2mg dl and the clearance is 200 mlhr. What is the time required to reach steady state plasma concentration -l0hrs20hrs30hrs40hrs  <response>: Ans. is b i.e., 20 hourso Volume of distribution total doseplasma concentrationo Total dose dose kg x body weight 100 x 20 2000 mgo Volume of distribution 20002 1000o Half life 0?693 x Volume of distribution clearance 0?693 x 1000200 3?5 hourso Time required to reach steady state plasma concentration is 5-5 half lives 5?5 x 3?5 19?25 hourso Therefore the most appropriate answer is 20 hours. 