Pharmacokinetics Flashcards
What is pharmacokinetics?
Pharmacokinetics is the effect the body has on drugs
Lost the 4 main components of pharmacokinetics.
Absorption
Distribution
Metabolism
Elimination
What is enteral drug administration? List 3 examples.
Enteral drug administration is delivery into the internal environment of the body via the gastrointestinal tract - 3 examples include -
- oral
- sublingual
- rectal
In the gastrointestinal tract where does the majority of dug absorption occur?
In the small intestine
What is the typical transit time in the small intestine?
Around 3-5 hours
What type of drugs moves through the plasma membrane via passive diffusion?
Lipophilic drugs (e.g. steroids) and weak acids/bases
What is pKa?
The pH at which 50% of a molecule is ionised
Is solute carrier transport an active or passive process?
A passive process that is based on a molecules electrochemical gradient
What molecules are transported via facilitated diffusion?
Cations and anions with with a net positive or negative ionic charge
List 7 factors that may influence drug absorption.
Surface area Drug lipophilicity Density of solute carrier transporters Blood flow Gastrointestinal motility pH Food
What is parenteral drug administration? List 3 examples.
Delivery of a drug via any route other than through the gastrointestinal tract - 3 examples include -
- intravenous
- subcutaneous
- intramuscular
What are phase I and phase II enzymes? Where are they highly expressed?
Phase I enzymes are cytochrome P45 enzymes, phase II enzymes are conjugating enzymes - both of these are highly expressed in the liver
Define bioavailability.
Bioavailability is the proportion of a drug which enters circulation when it enters the body and as such is able to have an active effect
How do you calculate oral bioavailability?
Oral bioavailability is the amount of drug reaching circulation / the amount of the total drug given
How many litres of extracellular fluid are there in the body?
14 litres
What is the ‘apparent’ volume of distribution?
This summarises a molecules move man out of the plasma, through the interstitium, and into the cellular compartment - it provides a summary measure of the behaviour of a drug molecule in distribution
What might a large volume of distribution suggest about a drugs properties?
The drug may be lipophilic
What does a small volume of distribution suggest about a molecules ability to penetrate different surfaces within the body?
It has poor penetration
How do you calculate a molecules volume of distribution?
The drug dose given / drug levels in the plasma
How do phase I and II enzymes metabolise molecules and ready them for elimination?
They increase their ionic charge, enhancing their renal elimination
What is clearance? How is this calculated?
Clearance is defined as the rate of elimination of a drug from the body - total body clearance = hepatic clearance + renal clearance
What is a topical drug treatment?
A drug applied to a particular area on the body (usually epicutaneous, applied to the skin), as opposed to systematically
What is ionotropy?
The force of muscle contraction
What is first pass metabolism?
The phenomena that details the reduction (via metabolism etc) of a drug before it reaches systemic circulation
Give an advantage and disadvantage of oral delivery of drugs.
Advantage - safest and most convenient method delivery
Disadvantage - drugs may be metabolised before systemic absorption
Give an advantage and disadvantage of intravenous delivery of drugs.
Advantage - immediate effects - valuable in emergencies
Disadvantage - strict aseptic methods needed
Give an advantage and disadvantage of intramuscular delivery of drugs.
Advantage - preferable to intravenous if self-administrated
Disadvantage - can be painful
Give an advantage and disadvantage of inhalation as a delivery of drugs.
Advantage - absorption is rapid - has immediate effects
Disadvantage - most addictive route - enters brain quickly
What is an enteric coating?
A covering applied to some enteric drugs to prevent them from being metabolised in the stomach, but allows their breakdown in the liver
