T11: Clearance from plasma half-life, dose and concentration
50. Pharmacokinetics 50.1) PK Basic parameters 50.1.2) Clearance
50.1.2.1) Clearance basic concepts Normal 1
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409.86 mg of a drug was administered to a patient as an IV push, which resulted the plasma concentration of 4.95 mg/L. The plasma half life of the drug is 2.85 h. Determine the clearance of the drug in this patient.
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lb equals 20.12 L/h kg
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We know that, clearance (Cl) is the product of elimination rate constant (K) and volume of distribution (V).
` Cl = K × V `.
In this case, we hav the dose of the drug administered (`X_{0}`) and the plasma concentration (`C_{0}`). We know that:
`C_{0} = X_{0}/V ⇒ V = X_{0}/C_{0}`.
From the relationship of `t_{½}=0.693/K`, we can calculate K as `0.693/t_{½}=0.693/(2.85 h)= 0.243 \quad h^{-1}`.
Therefore, clearance (Cl) will be:
`Cl = 0.243 \quad h^{-1} \quad × (409.86 \quad mg)/(4.95 \quad (mg)/L) = 20.12 \quad L/h`. Ans