Drug Absorption & Distribution

?
The two physical processes underlying drug disposition?
bulk flow and diffusion
1 of 51
The rate of diffusion mainly depends on its molecular size:
large molecules diffuse more slowly than small molecules
2 of 51
In the GI mucosa and renal tubule:
an epithelial barrier consists of cells tightly connected, molecules must transfers 2 cell membranes
3 of 51
The vascular endothelium and its anatomical disposition:
endothelial cells are packed with loose matrix proteins (filters), retaining large molecules and allowing smaller ones through (water permeates rapidly and molecules of 80,000-100,000 very slowly)
4 of 51
In the CNS and the placenta:
tight junctions between cells, the endothelium is encased in an impermeable layer of periendothelial cells (pericytes), which prevent potentially harmful molecules leaking from the blood into organs.
5 of 51
In the liver and spleen:
the endothelium is discontinuous allowing free passage between cells
6 of 51
Endocrine glands:
fenestrated endothelium facilitates transfer into the bloodstream through pores in the endothelium.
7 of 51
Molecules that dissolve freely in membrane lipids thus diffuse readily across cell membranes
Non-polar
8 of 51
The number of molecules crossing the membrane per unit area per unit time, and the concentration difference across the membrane. Is known as the?
permeability coefficient
9 of 51
What two physiochemical factors contribute to the permeability coefficient:
Solubility (Partition coefficient) & Diffusivity (Diffusion coefficient)
10 of 51
Lipid insoluble:
Ionised / Charged
11 of 51
Lipid Soluble:
Unionised / Uncharged
12 of 51
What is the lipid solubility of ionised species:
low lipid solubility therefore cannot cross cell membranes unless protein transport exists
13 of 51
What is the lipid solubility of unionised species:
high lipid solubility therefore can cross cell membranes although exceptions (aminoglycosides)
14 of 51
Asprin metabolism can be:
promoted by drugs that accelerate gastric emptying (metoclopramide) & retarded by drugs that slow gastric emptying (propatheline)
15 of 51
Urinary acidification:
increases excretion of weak bases and decreased excretion of weak acids
16 of 51
Urinary alkalisation:
decreases excretion of weak bases and increases excretion of weak acids
17 of 51
What effect on plasma pH can cause extraction of weakly acidic drugs from the CNS and the plasma
increasing plasma pH
18 of 51
What effect on plasma pH can cause extraction of weakly acidic drugs to accumulate in the CNS?
decreasing plasma pH
19 of 51
Levodopa is transported by the carrier:
phenylalanine
20 of 51
Flurouracil is transported by the carrier:
pyrimides
21 of 51
Iron is transported by the carrier:
in the jejunum
22 of 51
Calcium is transported by the carrier:
vitamin D-dependent
23 of 51
For a drug to permeate cell membranes it needs to be:
non-polar, unionised and lipophilic
24 of 51
Migraine, diabetic neuropathy
causes gastric stasis which decreases drug absorption
25 of 51
The effect of coeliac disease:
digoxin decreased, propranolol increased
26 of 51
Tetracycline collates with?
calcium ions
27 of 51
Bile acid binding resins (cholestyramide) interacts with?
warfarin and thyroxine
28 of 51
Vancomysin, Mesalazine and Olasazine are drugs which are...
not absorbed for therapeutic benefit
29 of 51
The amount of drug that reaches the systemic circulation intact& the rate at which it happens is know as?
systemic availability
30 of 51
In oil dosing factors intrinsic to formulation which effect bioavailability are?
the rate of disintegration of the tablet, the rate of dissolution of the drug particles in the intestinal fluid
31 of 51
Define bioequivalence?
two formulations which show comparable bioavailability and similar times to reach peak plasma concentrations
32 of 51
Define bioinequivalence?
two formulations of a drug with significant difference in bioavailability
33 of 51
Define therapeutic equivalence?
two drugs are therapeutically equivalent as they show comparable efficacy and safety
34 of 51
Example of a drug that is given by subcutaneous injection?
insulin
35 of 51
What formulation and use for formulations containing adrenaline?
local anaesthetics
36 of 51
Examples of controlled release formulations?
generic coated aspirin, quinidine
37 of 51
Examp drug which is packaged in liposomes?
amphofericin
38 of 51
The delivery of a drug from plasma to the intestium primarily depends on?
blood flow, capillary permeability, degree of the drug binding to plasma proteins, the hydrophobicity
39 of 51
Define the volume of distribution?
volume of fluid which the drug is disseminated
40 of 51
Plasma compartment:
Drug has large MW, or binds extensively to plasma proteins. Too large for slit junctions and is therefore trapped.
41 of 51
Extracellular fluid (interstitial):
Drug has low MW but is hydrophilic, can move through slit junctions but not through lipid membranes
42 of 51
Total body water (intracellular):
Drug has low MW and is hydrophobic , can move through slit junctions and cross cell membranes
43 of 51
Low dose capacity:
dose of drug is less than the binding capacity of albumin
44 of 51
High dose capacity:
dose of drug is much greater than the binding capacity of albumin
45 of 51
Drug displacement in relation to albumin:
class 2 drugs can displace class 1 which increases the pharmacology of class 1
46 of 51
Example of a class 1 drug?
tolbutamide
47 of 51
Example of a class 2 drug?
sulphonamide
48 of 51
Drug displacement and Vd: If Vd s large:
change in free drug concentration is insignificant
49 of 51
Albumin has strong affinity for?
anionic, hydrophobic drugs
50 of 51
What percentage is warfarin bound to albumin?
98%
51 of 51

Other cards in this set

Card 2

Front

The rate of diffusion mainly depends on its molecular size:

Back

large molecules diffuse more slowly than small molecules

Card 3

Front

In the GI mucosa and renal tubule:

Back

Preview of the front of card 3

Card 4

Front

The vascular endothelium and its anatomical disposition:

Back

Preview of the front of card 4

Card 5

Front

In the CNS and the placenta:

Back

Preview of the front of card 5
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