drugs Flashcards
Tmax
time to get to peak concentration
C max
peak concentration
increasing rate of absorption will
make the drug reach peak conc faster
what will increasing dose do
increase peak conc- C max
but wont increase time- T max
the area under the conc/time curve =
amount of drug that reaches systemic circulation
and biologics available
factors affecting oral bioavailability
- formulation- tablet, capsule, systemic
- ability to pass membrane
- gastrointestinal effects- gut motility, food, illness
- first pass metabolism
what effects membrane permeability
SIZE
solubility
ionisation
IONISED DRUG DON’T CROSS MEMBRANE
lipid soluble drugs will…
pass right across membrane
first pass metabolism
metabolism of a drug before it reaches systemic circulation
often causes problems for oral route
protein bound drugs are…
inactive
protein binding is ____ and effected by
reversible
effected by:
renal failure
pregnancy
other drugs
prodrugs are activated by
metabolism
what type of compounds can be excreted
water soluble
lipid compounds after use get
reabsorbed
main stages of phase 1 metabolism
hydrolysis
oxidation
reduction
increases polarity
main enzyme of phase 1 metabolism
cytochrome p450
helps to determine drug specificity
phase 1: CYP3A4 metabolises
many drugs inc diazepam and methadone
and found in gut for presystemic metabolism
“3A”LLLdrugs
phase 1: CYP2D6 metabolises
antidepressants and antipsychotics
codeine-morphine
“CYP2”Depressants
phase 1: CYP1A2 metabolises
theophylline
CYP1A2- the 1 looks like T for theophylline
phase 2 metabolism invlolves
conjugation
increases water solubility and enhances excretion
what does phase 2 metabolism include
adding:
glucuronic acid
glutathione
sulphate
acetate to metabolite
inactivating molecule
things that induce metabolism
smoking and alcohol
phenytoin
st johns wort
things that inhibit metabolism
erythromycin
clarithromycin
grapefruit juice
IV drugs and absorption
none absorbed
100% bioavailability
