Drug Distribution Flashcards
What is drug distibution?
- Movement of a drug to/from blood and tissues of the body
- Where does it get to / where doesn’t it
What are the factors that effect drug distibution?
- Cardiac Output and blood flow
- Plasma protein binding
- Lipid solubility
- pH of compartments
- Capillary permeability
What does the initial rate of distribution heavily depend on?
Cardiac Output and blood flow
How potent is albumin?
40g/L
What drugs bind to albumin? And where do they bind?
- Lipid soluble drugs (non-specifically)
- Weak acids (specific saturable site)
What can cause increased albumin (hyperalbuminemia)?
Dehydration
What can cause decreased albumin (hypoalbuminemia)?
- Burns
- Renal diseases
- Hepatic diseases
- Malnutrition
How does hyperalbuminemia affect free drug levels?
Decreases free drug levels
What lies beneath the basal membrane in the blood brain barrier which adds an extra layer of protection?
Astrocytes
Name a disease that can allow drugs to pass more easily through the blood brain barrier
Meningitis
What kind of drugs can pass through the placenta and into the foetal circulation?
- Lipid soluble drugs
- Unionised forms of weak acids and bases
What other areas have specialised barriers / compartments/
- Placenta
- Chronic abscesses
- Lung infection
What is the Volume of water in an average 70 kg adult?
42 litres
What is the volume of water in extracellular fluid?
15 litres
What is the volmume of water in plasma?
3 litres
What is the volume of water in the body that constitutes as intracellular fluid?
27 litres
What drugs bind to bone and have a long half-life?
Bisphosphanates
What is the volume of distribution?
May be a physiological volume
Theoretical volume that explains where the drug that has been added to a patient has gone
Explains the amount of plasma you need to work out where a drug has gone.
How is the apparent volume of distribution calculated?
(Total amount of drug in the body) / (Blood plasma concentration of drug)
What is the apparent volume of distribution (Vd)
Vd is the theoretical volume required to account for the amount of drug in the body
What does Vd vary with?
- Height
- Weight
- Age
- Fluid accumulation (ascites, oedema, pleural effusion)
- Accumulation of fat
When is apparent volume of distribution clinically relevant?
If you want to reach the peak plasma concentration using the bolus of a drug
What is the affect of increased volume of distribution of the half-life of a drug?
As volume of distribution increases the half-life of a drug increases
