Absorption/Distribution Flashcards
What is drug absorption?
Mass transfer process that involves movement of unchanged drug molecules from the site of absorption to the bloodstream
What is the rate limiting step for drug absorption?
Crossing the epithelia or endothelia
What is the rate of absorption related to?
Time
What is the rate of absorption measured by?
Time parameters (ka, tmax)
What is ka?
Absorption rate constant
What is tmax?
time for the drug concentration to reach maximum in the plasm
What is absorption t1/2?
The time for 50% of the administrated dose is absorbed
What is the extent of absorption related to?
Magnitude or amount of the drug reaching to systemic circulation
How is the extent of absorption measured?
Bioavailability (F) of the drug
What are the 4 factors influencing drug absorption from oral admin?
Type of dosage form
Physico-chemical properties of the drug
Physio-anatomic condition of the host patient
Pathologic conditions of the host patient
What are the two main factors of physico-chemical properties of the drug
Aqueous solubility and permeability (log p)
What is the preferred route of administration?
oral
What do lipids and proteins in the blood do for circulating concentration of the drug?
Serve to increase the circulating drug concentration for certain aqueous insoluble drugs
What is permeability also dependent on?
pH (ionization)
What affects aqueous solubility and permeability?
Molecular weight
Ionization constant (pKa)
Solid state form
Particle size
What are charged species restricted to during absorption?
Paracellular pathway
What can drug release from the dosage form be affected by?
Excipients and manufacturing processes