Page 89 - Interactive Theoritical Notes of Bioharmaceutics and pharamcokinetics.docx compressed

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

What is the difference between Passive Diffusion and Active Transport

regarding their kinetics??
➢ For a drug absorbed by passive ➢ In contrast, when a drug is

diffusion, the rate of absorption absorbed by a carrier-mediated

increases in a linear relationship to process,

drug concentration. • The rate of drug absorption

. increases with drug concentration

until the carrier molecules are

completely saturated.

i.e. the rate of absorption reaches a

saturation point, at which time an

increase in drug concentration (larger

doses) does not result in a directly

Comparison of the rates of drug absorption of proportional increase in the rate of

a drug absorbed by passive diffusion (line A) absorption.

and a drug absorbed by a carrier-mediated This is because of a limited number of

system (line B). carriers in the membrane.

So, at higher drug concentrations, the

rate of drug absorption remains

constant, or zero order.

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