<prompt> The percentage of drug remaining in the plasma after 3 half life is6.2512612.50  <response>: HALF-LIFE of drug : The time taken for its plasma concentration to be reduced to half of its original value 1st t12 50 2nd t12 5025 75 3rd t12 502512.5 87.5 4th t12 502512.56.25 93.75 So Remaining is 100 - 87.5 12. 5 Note : Nearly complete drug elimination occurs in 4-5 half lives. Drugs eliminated by First order kinetics Zero order kinetics t 12 remains constant because V and CL do not change with dose. t 12 increases with dose CL progressively decreases as dose is increased t12 0.693 x Vd CL 