pharmacology Flashcards
physiochemical
react with each other
- adsorption
- chelation
- precipitation
- neutralisation
e.g. paracetamol overdose treated with activated charcoal as it sticks to the paracetamol
pharmacodynamics
the effect a drug has on the body
effects of drugs and mechanism of their action
types of drug interactions
summative= addition of drugs together is the same as just one of the drugs at the same dose
synergistic= two drugs together and overall effect is greater than the individual effect of one at the same dose ( 1+1>2)
antagonism= drugs oppose each other (morphine and naloxone)
potentiation= two drugs and only one makes the other more powerful
pharmacodynamic mechanisms
receptor based
signal transduction
physiological systems
Receptors and drug interaction
agonists
partial agonists
antagonists (competitive and non-competitive)
physiological systems
different drugs that effect different receptors but in same physiological system
Ca channel antagonist and beta blocker
ACE I and NSAID
pharmacokinetics
what the body does to a drug
absorption
distribution
metabolism
excretion
absorption
motility=decrease in motility will decrease absorption
acidity= balance between ionised and unionised particles of a drug. Ionised particles can’t pass through membranes but unionised can. Changing acidity changes balance between these particles
solubility
complex formation
direct action on enterocytes
bioavailability
distribution
protein binding- wont have clinical effect
travel to other tissues- such as fatty tissue
travel to effect site
if two drugs are highly protein bound, the clinical effect of both drugs will increase as less of the drug will bind so more drugs are free in the blood
metabolism
CYP450
inhibition
induction
CYP450 (metabolism)
haemoproteins
metabolise many substrates - endo/exogenous
class 1,2,3 are most important
inhibition (metabolism)
enzyme inhibitors
e.g. metronidazole slows down CYP450 pathway
induction (metabolism)
enzyme induction can cause a drug interaction
e.g. morphine- CYP450- morpine6glucuride (becomes more potent)
excretion
renal:
- ph dependant
- weak bases= cleared faster if urine is acidic
- weak acids= cleared faster if urine is basic
biliary (minor)
drug interactions
protein binding
enzyme induction and inhibition
acute kidney injury
grapefruit juice
risk factors- patient
polypharmacy
old age
genetics
hepatic disease
renal disease
risk factors- drug
narrow therapeutic index
steep dose/response curve
saturable metabolism
how to avoid interactions
prescribe rationally
BNF
ward pharmacist
product information leaflet
drug definition
a medicine or other substance that has a physiological effect when ingested or otherwise introduced into the body
drugability
the ability of a protein target to bind to small molecules with high affinity
sometimes called ligandability
types of drug targets
receptors
enzymes
transporters
ion channels
mainly proteins
receptor definition
component of a cell that interacts with a specific ligand and initiates a change of biochemical events, leading to observed effects
ligands can be exogenous (drugs) or endogenous (hormones, neurotransmitters)
types of receptors
ligand-gated ion channels, e.g. nicotinic ACh receptor
G protein coupled receptor, e.g. beta-adrenoceptors
kinase linked receptors, e.g. receptors for growth factors
cytosolic/nuclear receptors, e.g. steroid receptors
ligand gated ion channels
outside the cell is the receptor
ligand binds to it and a constitutional change occurs, opening the channel