Drug distribution Flashcards
Where does the drug go during drug distribution? start with sight of administration.
sight of administration -> Circulation -> Tissue/ extravascular fluid->Where it is active
Name 4 factors that effect drug distribution.
1- plasma protein binding
2- tissue perfusion
3- disease and other drugs
4- elimination
What plasma proteins do drugs bind too (reversibly) ?
Albumin
Alpha1-glycoprotein
Is a drug biologically active or inactive when it is bound to a plasma protein?
Inactive.
What 3 things affect the amount of drugs bound to protein?
Pregnancy
renal failure
hypoalbuminaemia (low albumin levels)
How much of the drug must be bound to the protein for it to be an important factor?
Over 90% bound. Tissue distribution must also be small.
What 3 diseases affect drug distribution ?
Renal failure
Liver disease
Obesity.
What is the Vd?
Volume of distribution - Amount of drug that is diffused through membranes and in tissues and blood.
What is clearance?
The volume of fluid from which a drug is completely removed over time.
What is a half life?
The time taken for the drug concentration in blood to half.
How does Vd affect clearance?
Higher Vd = more time for clearance
what happens if half life is prolonged?
More drug toxicity.
What does half life depend on?
Clearance and Vd
What are the two parts to drug elimination?
Drug metabolism
Drug excretion
Where does drug metabolism occur?
liver
Where does drug excretion occur?
Kidney and billiary system
What drugs are filtered by glomuler filtration?
Any unbound drug
What drugs are filtered by active tubular secretion?
Anionic and cationic drugs. (+ and - ones)
What type of drug can undergo passive tubular reabsorption? this is where filtrate travels down renal tubule, the drug gets more concentration, and then is absorbed back into circulation.
De- ionised drugs.
How are drugs secreted into bile?
Passively or actively.
What is the word for when drugs are reabsorbed back into circulation from the bile?
enterohepatic circulation.
when can enterohepatic circulation continue until?
The drug is metabolised in liver or excreted by kidney.
What does the metabolism in the liver do to the drug?
conjugates it ( adds another molecule) . this means it aint reabsorbed.
What is chronic administration?
when drugs are administered over a period of time.
What is steady state conc?
When drugs stays at steady conc.
