Cardiff Q - Pharmacology Flashcards
Pharmacokinetics
What body does to drug
Absorption, distribution, metabolism, etc
Pharmacodynamics
What the drug does to the body
Methods of drug action / targets
Receptors
Ion channels
Enzymes
Hormones
Neurotransmitters
Transport systems
Physicochemical
Receptor definition
Proteins integral to a cell membrane
Ligand definition
A substance able to bind to a receptor
Full agonist
Binds to receptor and produces maximum response
Partial agonist
Binds to receptors but produces submaximal response
Inverse agonist
Binds to receptor but produces opposite effect to endogenous agonist
has affinity but efficacy = -1
Allosteric modulator
Binds to receptor at a separate site to that of the endogenous agonist
Changes conformational shape
Can affect affinity and efficacy
Factors which affect ability of molecule to pass through cell membrane
Molecular size
Concentration gradient
Ionisation and pKa
Lipid solubility
Protein binding
pKa
Lipophilic cell membrane only allows uncharged portion of a drug through
pKa = the pH at which 50% of the drug is ionised and 50% of the drug is unionised (-log10 [Ka])
Ka = acid dissociation constant
The lower the pKa, the stronger the acid
For an acid drug: if pH > pKa = more ionised, therefore less effective / slower onset time
For a base drug: if pH < pKa = more ionised, therefore less effective / slower onset time
Here the pH relates to the environment to which the drug is administered - eg may be blood pH, or may be abscess pH (eg why local anaesthetics don’t work in pus areas)
Acid definition
Proton donor
H+
Base definition
Proton acceptor
OH-
Acid examples of drugs
Aspirin
Thiopentone
Paracetamol
Propofol
Atropine
Furosemide
Some effects of protein binding ton drugs
Only unbound portion of drug in plasma is free to cross the cell membrane
Albumin binds acids
Bases example of drugs
Opioids
Local anaesthetics
Ketamine
Midazolam
Etomidate
Diazepam
Isomer definition
Molecules with the same molecular formula but different anatomical arrangement
Can be structural isomer or stereo isomer
Structural isomer
Different arrangement of elements / chains
Stereo isomer types
Geometrical isomer (aka cis-trans isomer) - different orientation around a double bond
Optical isomer (aka enantiomer) - mirror images
Volume distrubution
Theoretical volume which the drug must disperse in order to produce a measured plasma concentration
Affected by lipid solubility, tissue protein binding….
Bioavailability
Fraction of drug administered that reaches the systemic circulation
Context sensitive half time graph of various anaesthetic drugs - need to learn this for viva
