(3) Pharmacokinetics (Wolff) Flashcards
What are the four basic pharmacokinetic processes?
ADME
Absorption, Distribution, Metabolism, Excretion
What factors can affect drug absorption?
Rate of dissolution
Surface area
Blood flow
Lipid solubility
pH partitioning
What is the most common way that drugs travel accross the membrane?
SIMPLE DIFFUSION
What type of drug can readily cross a cell membrane?
Non polar drugs
Could these compounds cross the membrane?
NO!!!
Quaternary ammonium compounds have a fixed charge and CANNOT readily cross cell membranes
When can weak acids and weak bases cross membranes?
ONLY when they are in their unionized form
Aspirin is a weak acid.
Where would it be well absorbed?
Where would it be trapped?
Stomach.
Trapped in basic compartments.
Amphetamine is a weak base.
Where would it be well absorbed?
Where would it be trapped?
NOT the stomach.
Trapped in acidic compartments
Pharmacokinetic Math Terms
Ka =
S =
F =
Amount absorbed =
Ka =rate constant for absorption
S = “salt factor”
F = bioavailability, fraction of drug that reaches the bloodstream
Amount absorbed = S * F * Dose
How do you calculate bioavailability?
What are the factors that affect drug distribution?
Ability of drugs to enter the cells
Blood flow to tissues
Ability of drugs to exit the vascular system
What is the significance of protein binding of drugs?
You can get partial retention of drugs in vasculature
*There are a finite # of protein binding sites in the plasma, due to this, the addition of new drug can displace the bound drug
DRUGS ARE ONLY BIOACTIVE IF FREE (use alpha to denote free)
What are special considerations you must make with drug admin. w/ the blood brain barrier?
In an adult, ionized/polar drugs will not cross the BBB unless there is a specific transporter
This is why LIPID drugs are the typical class of drug to target the brain
How do you calculate the concentration of drug in the plasma?
How do you calculate the volume of distribution (Vd)?
