A patient was given a 200 mg dose of a drug IV, and 100 mg was eliminated during the first 2 hours. If the drug follows first-order elimination kinetics, how much of the drug will remain 6 hours after its administration

One half of the dose is eliminated in the first 2 hours so its elimination half-life equals 2 hours. With the passage of each half-life the amount in the body (or in the blood) will decrease to 50% of a former level. Thus, at 6 hours after administration, 3 half-lives have passed: (1) 200 mg to 100 mg, (2) 100 mg to 50 mg, and (3) 50 mg to 25 mg. Ref:- kd tripathi; pg num:-32 Plasma half-life:-