T05) Find k from C0, Ct and t.

50. Pharmacokinetics 50.2) Plasma concentrations over time 50.2.1) Plasma concentrations over time

T01: Later plasma concentration Normal 1

Total tried:       Correct:       Wrong:

For an intravenously administered drug, if the concentration at 5 hr is 4.06 mg/mL, and concentration at 16.9 hr is 0.223 mg/mL, then determine the elimination rate constant of the drug. Assume that the drug follows a first order kinetics.

Click on the button below to see the answer and explanations

lb equals 0.244 h-1 kg

    For a first order process,
    It may be re-organized as:
    `∴ k = ln(C_{0}/C_{t})/t`
    Difference between two time points (16.9 hr and 5 hr) is 11.9 hr.
    `\implies k =(ln(4.06/0.223))/11.9`
    Or, `k = 0.244`
    Thus, the rate constant is `0.244 \quad h^{-1}`. (Ans).