3 Flashcards
(27 cards)
Pill negatives
patient compliance, drug absorption is slower and rapid metabolism may cause failure to reach an optimum concentration.
With pills,
OD is less likely due to absorption and time to react.
With pill absorption,
time and surface area matter. Mouth and esophagus arenty too important, colon is not important, as the drug is gone by that time.
Main site of pill absorption
stomach and small intestine.
Most drugs have to be ——— enough to get throguh numerous cell membranes during absorption
lipophilic
The larger the ——the more likely drug will be absorbed by passive diffusion
partition constant
Pores are
always open
ABC transporters (use ATP) can
kick drugs out of cells - can be overexpressed, creating drug resistance. Problem is that these aren’t specific for one drug, so they can leadto resistance of a group of drugs.
SLC transporters (exchange Na+ or K+) important for
transport of certain drugs that are organic acids or bases
Intravenous are faster to ———, can’t affect ——–
difuse
adverse effects/limit them easily
Intramuscular/subcutaneous
i) Good if problems with enteric absorption or inactivation
ii) Many smaller drugs absorbed similarly as from the gut with these routes and bigger things as well as proteins can get in through gaps.
For intramuscular/subcutaneous, ———— can retard absorption (diminish circulation)
Vasoconstriction
Topical = Absorption of some ——– drugs enhanced by ——
lipophilic
solvents (DMSO)
Water soluble drugs move through —-
endothelial gaps and are lsower
Bigger proteins move into blood from
transcytosis - vesicles that form and are internalized.
Restricted distribution into CNS- blood brain barrier
No gaps in endothelium, sheath surrounds, drugs efficiently transported out of endothelium back into blood stream
Q/C = Vd, the volume of distributio
Q = initial mg of drug, C = mg/L of plasma sample after a bit.
Vd higher than total fluid volume (41L)
means it’s going somewhere (sticking to protein, tissues), drug is getting metabolized, excreted, leading to low concentration in plasma
The volume of distribution (VD) is the
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 plasma. It is defined as the distribution of a medication between plasma and the rest of the body after oral or parenteral dosing.
Drug metabolism
Phase I: Add (uncover)
functional group (make more polar)
Usually done through oxidations (P450 enzymes, flavin monooxygenases
Drug metabolism
Phase II:
Conjugation
Smooth E.R. of hepatocytes:
membrane bound enzymes that metabolize drugs (microsomes)
Morphine inactive,, but 6-glucuronide is
active form - done in smooth er of hepatocytes
Non microsomal metabolism (in liver and other tissues)
Microsomal enzymes designed to remove foreign substances
Non-microsomal metabolism when drug mimics natural substance
