Pharmacokinetics Flashcards
what is pharmacokinetics?
the study of what the body does to a drug
What does ADME stand for?
A - absorption (how drug gets into body)
D - distribution
M - metabolism (how body chemically modifies drug)
E - excretion (how the body removes drug)
What is the C-MAX?
Maximum concentration of drug in body = top point of the graph
This can help predict therapeutic benefits and the likelihood of side effects
What is T-MAX
The time in which C-MAX occurred
What is the half life of a drug
time it takes to remove half of the current concentration of drug from the body
What is the area under the curve on a drug graph
total exposure to drug that the body receives
What is the definition of absorption?
movement of a drug across a biological membrane from
the site of administration to the systemic circulation
what is absorption dependent on
-Lipid
solubility/ionisation
-Solubility
-Concentration gradient
-Bioavailability
-Molecular size
-Blood flow
-Membrane surface area
-Membrane permeability
What is ionisation?
atom or molecule with a net charge
ionisation = adding H+
Drugs exist in BOTH ionised and unionised forms (often weak base or weak acid)
more H+ = more acidic
Ionised cannot pass through phospholipid bilayer as they have a ‘shell’ of water molecules
Water soluble drugs = ionised
Lipid soluble = unionised drug
*drugs are only absorbed if they are unionised
What is bioavailability?
the proportion of the unchanged drug that passes into the systemic circulation
what is first-pass metabolism
orally administered drugs undergo pre-systemic metabolism in the liver
what is distribution?
reversible transfer of a drug between one location to another
as most drugs are very small molecular size, they leave the circulation capillary filtration to act on the tissue
What affects drug distribution?
-Blood supply
-Capillary permeability
-Lipid solubility
-Tissue binding
-Tissue-specific barriers
-Protein binding
What protein is the primary protein involved in plasma protein binding of drugs
Albumin
Drugs bound to albumin cannot pass through vascular wall
Correct
*see notes for further details
FACT
less albumin = more free drug = increased pharmacological effect
FACT
there is a condition called hypoalbuminaemia = low levels of albumin = increased pharmacological effect of drugs
Why do you have to be careful with hepatic impairment with certain drugs?
increased risk of accumulation and toxicity due to decreased protein binding in hepatic impairment
When drug is not highly bound to plasma proteins
= more is eliminated
What is half life?
time it takes for one half of the drug to be
eliminated by the body
Drug half life is variable and can be long or short
Subsequent doses are given to raise the
concentration levels to a peak
In theory, the optimal dosage interval between
drug administration is equal to the half-life of the
drug
What is the therapeutic threshold?
minimal amount of drug required to produce the desired response
