Drug Absorption and Distrubution Flashcards
Bioavailability
How well/ readily a drug is absorbed and reaches circulation
Lipophilic Drugs
They have an affinity for fat
are dissolved into fatty contents of the stomach or absorbed through the G.I. tract into the bloodstream in order to act
Usually oral medications
Hydrophilic Drugs
They are dissolved in water and diffuse through fluid to get into the bloodstream and act
Usually solutions which would be administered S/C or I/M routes (therefore injected into ECF before entering bloodstream)
How does a drug pass through the G.I membrane
Passive diffusion - high concentration to low concentration (bowel to cells)
Active transport - low concentration to high concentration (cells to bowel)
What will affect the rate oral medicine is absorbed?
Chemical nature of the drug
Preperation of the drug
Concentration (higher, quicker absorbed)
Alteration of gut motility (diarrhoea = faster bowel movement)
Contents of stomach (full may slow absorption)
Formulation
S/C or I/M injections
injected into ECF before diffusing into the bloodstream
how well drug absorbed in I/M route depends on what factors
How often the muscle is used (if well used will have a good blood flow)
If rub injection site
(rate of absorption is dependent on blood supply
What affects drug distribution once the drug is in the circulation
Plasma proteins
lipohilic/hypophilic
like absorption, drugs are distributed better to areas with greater tissue perfusion
Receptors
Receptors are protein molecules found within the cell that receive chemical signals from the drug and respond to them
the things which help the drug gain access to the receptor are the receptor sites but not all body cells have receptor sites for all drugs
Two types of drug that affect the receptors
Agonist - stimulates and activates the receptor (think domitor)
Antagonist - combines with the receptor but fails to initiate a response
(or stops the agonist from taking further action. I.e. antiseden)
Non specific drug
a drug that acts on many cells of the body
as a result have more side effects
