Absorption from GIT 3 Flashcards
Which order do oral drugs normally take
1st order
What is the equation of the rate of absorption for 1st order kinetics?
Ka x Aa
Ka - absorption rate constant
Aa - amount remaining to be absorbed
How is Cmax defined in relation to absorption and elimination?
rate of absorption equal to rate of elimination
What is tmax?
How long it takes to get to Cmax
What is the equation of drug administered orally?
F x Dose = CL x AUC
If all factors remain constant will Cmax and Tmax differ?
Cmax will increase or decrease
Tmax - no change
If a drug is absorbed lymphatically what are the 3 pathways?
Micro/nano particles via peyer’s patch
v large water soluble macromolecules too big for capillaries
lipophilic drugs with chylomicrons
How are lipids absorbed
enter small intestines as droplets
bile salts & pancreatic fluids secreted
biliary lipids bind to surface of emulsified lipid improve colloidal stability & reducing particle size
How does Pancreatic lipase work?
acts mainly in sn-1 & sn-3 positions of triglyceride to release one molecule of 2-monoglyceride & two molecules of free fatty acids
Why is co-lipase needed to break down lipids?
the triglyceride covered with bile acids are not accessible for P-lipase, so binding of co -lipase helps bind lipase molecule on surface of lipid/aqueous layer
Why do micelles help uptake of lipids into enterocyte?
micellar solubilisation of monoglyceride & FAs help diffuse products into enterocyte
How do FAs cross membrane of enterocyte?
Low FAs conc - via transporter
High FAs conc - passive diffusion
