Back to the Top
I have one question regarding carrier mediated absorption.
If a drug absorption is carrier mediated . Administration of such drug at high dose (above saturation) follows zero order absorption (because of capacity limited transportation) but what about drug concentration which is below transporter saturation level?.
Will absorption be depend on X (amount of drug) at sub saturation case or transporter will transport all the molecule inside (in to the circulation) post to release from formulation and again zero order kinetics (absorption) will be followed (As no. of transporters are more than no of drug molecule released and all molecules will be transported at a time and again will be ready to transport new released molecules and so on.As a result transportation of drug inside is controlled.
Can we say zero order absorption again even at sub saturation levels?
BITS-Pilani, Hyderabad Campus
Back to the Top
Since the number of carriers is limited, the system is capacity-limited i.e. at higher concentration, the system becomes saturated and approaches an asymptote.
It is important to note that for a drug absorbed by passive diffusion, the rate of absorption increases linearly with the concentration but in case of carrier-mediated process, the drug absorption increases linearly with concentration until the carriers become saturated after which it become curvilinear and approach a constant value at higher doses.
Such capacity-limited process are called mixed order kinetics, because it is first order at sub-saturation drug concentration and apparent zero order at and above saturation level.
Hope it may help u.
Sr Research Associate-Bioanalytical
Veeda Clinical Research
Want to post a follow-up message on this topic?
If this link does not work with your browser send a follow-up message to PharmPK@boomer.org with "Carrier mediated absorption" as the subject
Support PharmPK by using the
Copyright 1995-2011 David W. A. Bourne (email@example.com)