where does most oral drug absorption occur
small intestine
rate of absorption from fastest to slowest
IV, SL, ODT, IR tabs, ER tabs
enteric-coated frug formulations
dulcolax
budesonide
example of high bioavailability
levofloxacin
linezolid
oral and IV does are the same
100% oral dose absorbed
factors that favor passage across membrane and greater distribution to the tissues
high lipophilicity
low MW
unionized
low protein binding
corrected calcium=
= cal reported + [(0.4 - alb) x (0.8)]
corrected phenytoin
(0.2 x alb) + 0.1
Vd =
concen. of drug in plasma
primary site for drug metabolism
gut and liver
first past metabolism
reduce the bioavailability
this drug first pass metabolism is so extensive that the drug cannot be given po
lidocaine must be IV
where does excretion primarily occur
kidney (urine)
gut (feces)
Bioavailability (F) =
AUC extra x Dose Intra
————————————— x 100
AUC intra x Dose Extra
clearance (Cl) =
Rate of Elimination F x Dose
—————————— or ————–
Drug concentration AUC
first order elimination
MOST DRUGS
constant PERCENTAGE of drug removed per unit of time
linear relationship between dose and serum levels
zero order elimination
constant AMOUNT of drug removed per unit of time
which drugs exhibit michaelis menten kinetics (saturable, mixed order or nonlinear kinetics)
phenytoin
theophylline
voriconazole
increase dose = disproportionate increase on drug concentration at steady state
how should phytoin dose adjustments be done when >7 mcg/ mL
small increments
elimination rate constant (Ke) =
CL/ Vd
half life =
0.693/ ke
Loading dose =
F
lives to reach ss
5
noyes whitney
rate of dissolution formula
before any orally administered drug is absorbed it must be …
dissolved
