Pharmacokinetics Flashcards
is the protonated form of a weak acid ionized or non-ionized?
non-ionized
is the protonated form of a weak base ionized or non-ionized?
ionized
do ionized or non-ionized forms of molecules cross membranes more easily?
non-ionized
definition: pKa
pH at which 50% of drug is ionized and 50% is non-ionized
if the pH is less than the pKa of a drug, which form predominates?
protonated
if the pH is greater than the pKa of a drug, which form predominates?
unprotonated
are weak acids protonated or unprotonated in the low pH environment of the stomach?
protonated (non-ionized)
are weak bases protonated or unprotonated in the high pH environment of the intestines?
unprotonated (non-ionized)
what factors affect drug distribution?
- cardiovascular
- tissue binding
- molecule size
- lipid solubility
definition: phase I biotransformation
- generates more polar molecule by exposing functional group on parent compound
- readies compound for phase II
definition: phase II biotransformation
yields a more water soluble conjugated product to be excreted
what types of reactions occur under phase I biotransformation?
oxidative, reductive, hydrolytic
what types of reactions occur under phase II biotransformation?
- glucoronidation, sulfation, acetylation
2. glutathione conjugation, glycine conjugation, methylation, water conjugation
definition: first pass effect
- drug absorbed by the stomach or intestine will initially be carried to the liver by the portal vein
- orally administered drug will be exposed to metabolizing enzymes by the liver
- drug can be inactivated prior to reaching the intended target
what is the mechanism of drug elimination?
kidney
drug elimination in the kidney depends on what factors?
- GFR
- binding to plasma proteins
- alkalinization or acidification of urine
what are the two key parameters that impact drug dosage?
- volume of distribution
2. clearance