15.10 Pharmacology: Advanced Pharmacokinetics Flashcards
What are the following terms called?: Giving the drug Drug entering circulation Drug spreads through the body Drug removal from the body
Administration
Absoption
Distribution
Elimination (chemical: metabolism, physical: excretion)
What is the use of the liver converting things into metabolites?
More water soluble so able to be excreted
What does the ‘clearance’=?
=extraction ratio x blood flow
What is renal clearance?
Amount of blood from which drug is removed by kidneys/time
What is maximal GFR and maximal CLrenal?
GFR: 120mL/min
CLrenal: 800mL/min
What is the equation for the CLtotal?
CLtotal= CLrenal + CLhepatic +CLother
What does renal excretion/drug metabolism depend on?
Concentration on drug in blood
Most drugs distribute…..
Rapidly
Most drugs are eliminated at a rate proportional to….
concentration in plasma (first order kinetics)
The amount of drug in the body falls……… …. ….. (first order elimination-IV)
The amount of drug in the body falls exponentially with time
What are the features of rapid IV administration (first order elimination) ? (3)
Rapid rise in body
Drug has half life
Peak concentration related to dose
What does the curve for a short term IV infusion look like?
Like a wave
What are features of short term iv infusion? (3)
Rate of accumulation decreases as concentration increases
Peak not as high as IV bolus
After infusion is over, get elimination only (simple first order)
What is short term iv infusion useful for?
For drugs with a narrow therapeutic window, e.g. gentamycin
What are the features of long term IV infusion (one compartment model, first order elimination)? (2)
- At steady state, rate of infusion=rate of elimination
- Css is proportional to infusion rate (easy to dial up to a particular concentration)
What happens in multiple dosing?
Trough will be half of the peak (if drug is given every half life): 2 fold variation to steady state
What is a loading dose?
We avoid lag time by bringing concentration up and then maintaining it (quicker)
How does absorption following oral administration take place primarily?
Via lipid diffusion
What is first pass hepatic metabolism?
Following oral administration, drug enters hepatic portal vein and is transferred directly to the liver
What are the features of oral administration (first order elimination)? (2)
Peak not as high as with IV
Not all of drug may be absorbed, some may undergo first pass metabolism
What does bio availability mean?
Proportion of active drug which enters systemic circulation (need to take this into account when calculating dose, administer more if low bio availability)
