T03) Find C0 from Ct, k 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:
A 168 -kg patient has received an IV bolus injection of a drug. A sample of blood was collected 5.8 hours after the first collection. The drug follows a first order elimination process, and its elimination rate constant is `0.247 \quad h^{-1}`. If the plasma concentration was 0.177 mg/L in the second sample, then what was the concentration in the initial sample?
Click on the button below to see the answer and explanations
lb equals 0.74 mg/L kg
-
For a first order process,
`C_{t}=C_{0}×e^(-kt)`
It may be re-organized as:
`C_{0}=C_{t}/(e^(-kt))`
Or, `C_{0}=C_{t}×e^(kt)`
Plugging the values in above equation, we get:
`C_{0}=0.177 × e^(0.247 × 5.8)`
`∴ C_{0}=0.74`
Thus, the initial concentration was: 0.74 mg/L. (Ans).