M&R Session 9- Pharmacokinetics Of Drug Administration Flashcards
During drug administration, when will a steady state be reached?
After 5 half lives of the drug.
What is the advantage of parental administration?
Concentrates the drug at the site of action and therefore reduces systemic absorption and unwanted side effects.
What is needed if an immediate effect of the drug is needed?
A loading dose.
What 3 things do you need to consider when getting a drug into a patient (pharmaceutical process)?
- the formulation of the drug- tablet or liquid
- compliance of the drug
- the site of administration.
What is oral bioavailability and what is it expressed as?
It is the proportion of an oral dose of a drug that reaches the systemic circulation unchanged.
Amount and rate.
What is the therapeutic ratio?
The maximum tolerated dose/the minimum effective dose.
What is first pass metabolism?
The phenomenon that drugs taken orally will travel from the gut to the liver where they could be prematurely metabolised before reaching the systemic circulation.
How is first pass metabolism avoided?
Giving a drug via a parenteral, sublingual or rectal route.
What is 1st order kinetics?
When the rate of elimination of the drug is proportional to the drug level.
What is zero order kinetics?
When the rate of drug elimination is constant.
How are drugs metabolised in the liver?
Phase I- the drug is made more active by oxidation, reduction or hydrolysis by an enzyme system- cytochrome P450.
Phase II- this reactive intermediate is conjugated with a polar molecule through glucaronidation or sulphate conjugation to make the drug water soluble and inactive.
When is the fact the enzymes are inducible and inhibitable important?
- when the drug has a low therapeutic ratio
- when the drug is being used at its minimum effective concentration
- when the drug metabolism is of zero order kinetics
Which drugs are excreted by the kidney?
Ionised
Lipid insoluble
What is the volume of distribution of a drug?
The theoretical volume into which a drug has distributed if this occurred instantaneously.
When do drugs exert an effect?
When they are free/unbound.
