Pharm 4 - Pharmacokinetics and Drug Metabolism Flashcards
State the 5 stages of the journey of a drug through the body.
Administration Absorption Distribution Metabolism Excretion
What is the difference between enteral and parenteral administration?
enteral = using GI tract parenteral = everything but the GI tract
What are the advantages of IV administration?
Rapid + high bioavailability
State two ways in which drug molecules move around in the body.
Bulk Flow Transfer
Diffusion transfer
State 4 ways drugs can cross lipid membrane barriers.
Diffusion through lipid membrane if lipid enough
Diffusion across aqueous pores
carrier moleculues
pinocytosis
Most drugs are either …
weak acids or weak bases
Which factors affect the ratio of ionized to non-ionised drug?
pKa of the drug
pH of the environment
Describe and explain the difference in absorption of aspirin in the stomach and in the small intestine.
Aspirin has a pKa of 3.4
in the acidic conditions of stomach, aspirin takes an unionised form.
because it is unionised it is rapidly absorbed.
in the small intestine, the pH is much more basic, higher pKa than the pKa of aspirin. So aspirin exists in an ionised form. This is not absorbed quickly.
What is ion trapping?
Some ionised aspirin will enter systemic circulation
there it will exist in an ionised form
because it is ionised it cannot move into tissues
therefore ‘trapped’
State 4 factors affecting drug distribution
Regional blood flow
extracellular binding
capillary permeability
localisation in tissues
In which state can albumin bind to drugs, ionised or non-ionised?
Both
State three types of capillary architecture.
Continuous
Fenestrated
Discontinuous
Give a broad example of localisation of a drug in tissue.
Lipophilic drugs tend to localise in fatty tissue e.g. brain and testes
What are the two main routes of drug excretion?
Kidneys - main
Liver
What type of molecules tend to get excreted via the biliary route?
Large molecular weight molecules
