Page 51 - Interactive Theoritical Notes of Bioharmaceutics and pharamcokinetics.docx compressed

PharmD clinical pharmacy program Level 3, Semester 2 Biopharmaceutics & Pharmacokinetics (PT608(

The rate of change in the amount of drug in the body, dX/dt, is dependent on the

relative rates of drug absorption and elimination.

The net rate of drug accumulation in the body at any time is equal to the rate of

drug absorption less the rate of drug elimination, regardless of whether absorption

is zero-order or first-order.

dX/dt = KaXa - KX

 However, since we cannot measure the amount of drug remaining to be absorbed

(Xa) directly, because of practical difficulty, we go to other alternatives such as
monitoring drug in the blood and/ or urine to determine the absorption rate constant

and the absorption characteristics.

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