T09: Clearance from plasma half-life and volume of distribution.
50. Pharmacokinetics 50.1) PK Basic parameters 50.1.2) Clearance
50.1.2.1) Clearance basic concepts Normal 1
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The elimination half life of a drug is 2.69 h. It is administered as an IV bolus to a 131 Kg patient. If the volume of distribution of the drug is 0.44 L/Kg, then calculate the clearance of the drug in this patient's body.
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lb equals 14.871 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 `.
From the relationship of `t_{½}=0.693/K`, we can calculate K as `0.693/t_{½}=0.693/(2.69 h)= 0.258 \quad h^{-1}`.
Also, the total volume of distribution will be the product of volume per Kg body weight and the weight of the patient. Thus,
` V = 0.44 \quad L/(Kg) × 131 \quad Kg =57.64 \quad L`.
Plugging the values in the first equation we get:
` Cl = 0.258 \quad h^{-1} × 57.64 \quad L = 14.87 \quad L/h ` Ans.
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