RPA pharmacology Flashcards
first pass metabolism
everything that happens from consuming the drug until the drug reaches the rest of the body
digestive -> portal system -> liver
oral bioavailability
AUC oral/ AUC IV x 100%
clearance in pharmacology
CL is expressed in L/min
the volume from which the drug is cleared per unit time
first order kinetics
clearance is related to the concentration of the drug
there is an exponential decay
zero order kinetics
the amount that is removed from the body is fixed
e.g. if an enzyme system is saturated
what are examples of drugs that operate at zero order kinetics
alcohol, aspirin, phenytoin, theophylline
does metabolism make the drug more polar or non polar
more polar so they can be excreted in urine
extraction ratio
fraction of drug removed from blood in one passage across organ (liver)
ER = (drug in - drug out)/(drug in)
what is flow dependent kinetics
when all drug is removed in the liver
clearance is approaching hepatic blood flow
what is capacity limited metabolism
when the ER approaches 0
examples of low extraction ratio
diazepam, carbamazepine phenytoin, warfarin
examples of high extraction ratio
morphine propranolol gtn CCB antidepressants levodopa
volume of distribution
theoretical volume that would be necessary to contain the total amount of an administered drug at the same concentration that it is observed in the blood plasma
volume distribution - amount in body/plasma concentration
Vd is defined as the apparent volume into which a drug disperses in order to produce the observed plasma concentration”
how to calculate loading dose
volume distribution x plasma concentration
greatest impact on pharmacokinetics in older people
decreased hepatic flow
age selective impairment of phase I>II (CYP >conjugation)
doxycycline birth defects
third trimester
teeth
what happens to volume distribution in pregnancy
increases
what happens to protein binding in pregnancy
decreased protein binding
need to think about when interpreting drug concentrations
p glycoprotein
drug transporters that determine the uptake and efflux of a range of drugs. This process affects their plasma and tissue concentrations and ultimately their final effects. P-glycoprotein functions as a transmembrane efflux pump, pumping its substrates from inside to outside the cell.
drugs are often both substrates of CYP3A4 and P-glycoprotein
what drug is most likely to cause addisonian crisis on adrenal replacement
rifampicin
pharmacodynamics
impact of the drug on the body
can be divided into effect and potency
potency is how quickly you get a response initially
effect is total effect on the body
hysteresis - negative vs positive hysteresis
negative hysteresis is where the drug effect increases despite same concentration because it is reaching the appropriate compartments over time
positive hysteresis is where the drug effect decreases despite the same concentrations due the toleration developing
Type A, B, C, D adverse drug reaction
type A is dose related
type B is idiosyncratic
anaphylaxis
C - chronic
D- delayed
