Pharmacokinetics Flashcards
What does ADME mean?
Absorption
Distribution
Metabolism
Excretion
All phases occur at same time
What is Pharmacokinetics?
The study and characterizationof drug absorption, distribution, metabolism andexcretion, with the aid of mathematical models which allow the data to be interpreted
What is Pharmacodynamics?
what the drug does to the body (pharmacodynamics) - drug/receptor interaction
What is clinical pharmacokinetics?
Clinical pharmacokinetics: A health science discipline dealing with theapplication of pharmacokinetics to the safe and effective therapeuticmanagement of the individual.
What does absorption mean?
The movement of a drug from the site of administration, across membranes into the bloodstream.
What factors affect the rate of absorption?
Route of administration
Dose (concentration)
Lipid-solubility
Weak organic acid/base drugs
What molecules are not efficient in passive diffusion
Carbohydrates, protein and ionised molecules
Efficient molecules include
hydrocarbons
anaesthetics
alcohols
lipids
most drugs
What are P-glycoproteins? what do they do?
Glycoproteins are proteins with carbohydrates attached.
P-gp in the apical cell membrane (facing the gut contents).
Substances are absorbed, but then actively pumped back into the gut contents (efflux).
ATP dependent.
Where are P-glycoprotein found and what is its function?
Intestine - prevents absorption
Liver - Excretion into bile
Kidney - Excretion into urine
brain- Prevent entry from blood into the brain
Example of Induction of P-gp?
Induction Example - Rifampicin increase the amount of P-gp in the intestinal epithelium. Reduces absorption of other substances.
Example of Inhibition of P-gp?
- Large enough dose of verapamil will saturate the P-gp. Other substances then absorbed more easily. Has been suggested as a means to increase absorption of problem molecules.
What is Bioavailability?
The fraction of a dose that reaches the systemic circulation in a chemically unaltered form
Fractional availability = F
Quote as percentage or decimal
e.g. 25% or 0.25
Has no units
How can bioavailability fail?
- Failure of disintegration
or dissolution - Chemical, enzymatic
or bacterial attack - Failure of
absorption & pGP efflux - First pass metabolism
in gut wall or liver
Binding to other molecules in the gut contents
Too polar to undergo passive diffusion
Efflux due to P-glycoproteins
What are the different routes of administration?
Orally
Rectal (suppository)
Injection (parental) - intradermal injections, Intravenous injections, Subcutaneous injections, Intramuscular injections, intravenous injection
Topical agents
Inhaled administration
Buccal - teeth and lip
Sublingual - under tongue
What is passive diffusion?
Small, hydrophobic molecules,
