Pharmacology - Drug Administration, Absorption & Distribution (Exam 1) Flashcards
1
Q
drug enters the plasma
A
absorption
2
Q
drug transported to and from sites of action
A
distribution
3
Q
Chemical structure of drug changed
A
biotransformation (metabolism)
4
Q
irreversible loss of drug
A
excretion
5
Q
loss of drug concentration or effect through distribution, biotransformation, excretion
A
elimination
6
Q
routes for drug entry
A
- enteral
- paraenteral
- inhalation
- local
7
Q
The delivery of any medication that is absorbed through the GI Tract
A
enteral
8
Q
enteral routes
A
- oral
- sublingual
- rectal
9
Q
occurs via injection
A
parenteral
10
Q
parenteral routes
A
- intravenous
- intramuscular
- subcutaneous (under skin)
- intrathecal (intraspinal)
11
Q
direct application of drug to its site of action
A
local
12
Q
local routes
A
- topical
- intradermal (into skin)
- intrasynovial (into joint space)
13
Q
what is the most common route of drug administration?
A
oral
14
Q
general traits for oral route
A
- convenient and economical
- requires pt compliance
- variable absorption (generally slower)
- safest (can be reversed by emesis if needed)
15
Q
When a drug is delivered orally, greater absorption occurs in the small intestine because?
A
Small intestine has a greater surface area
16
Q
factors that affect oral drug absorption
A
- gastric emptying time
- gastric acidity/presence of food
- first-pass effect
17
Q
where does the primary site for drug metabolism occur at
A
liver
18
Q
how does first pass effect occur? (enterohepatic cycling)
A
- drug taken orally
- drug dissolved in stomach
- drug is emptied in the small intestine
- drug absorbed through portal vein to the liver
19
Q
Some drugs cannot be given orally, and some can be given orally but at a higher dose because _____
A
it has to compensate for the 1st pass effect
20
Q
drugs administered via Intravenous (IV) are placed
A
into the vein (not artery)
21
Q
Absorption is ______ potentially causing immediate effects
A
circumvented
22
Q
when is intravenous useful
A
in emergencies
23
Q
intravenous permits
A
titration of dose
(exact amount of drug over time period)
24
Q
intravenous is suitable for ______ or ______
A
large volumes or irritating substances if diluted
25
intravenous is not suitable for ______ or ______
oily solutions or insoluble substances
(can produce embolism)
26
Intravenous must be injected slowly and is also _______ and _____
dangerous and expensive
27
What type of drugs are required for intravenous (2
high molecular weight protein or peptide drugs (cannot be given orally)
28
angle in subcutaneous parenteral route
45 degree
29
angle in intramuscular parenteral route
90 degree
30
angle in intradermal parenteral route
10 to 15 degree
31
where is an intramuscular injection placed?
into the muscle (not vein)
32
Intramuscular injections can have a ______ absorption from aqueous solution or a _____ and _____ absorption from repository preparations
prompt absorption from aqueous solution (fast) or a slow and substained absorption from repository preparations (last longer)
33
Intramuscular injections are suitable for (2)
1. moderate volumes
-2. oily vehicles
34
intramuscular injection are _____ and can cause _______
painful and can cause tissue damage
35
where are subcutaneous injections placed
beneath the skin
36
At rest, absorption of subcutaneous injections is similar to
intramuscular injections
37
Subcutaneous injections are useful for _____ or _____
insoluble suspensions or solid pellets
(gives very long and sustained administration w/o having to reinject)
38
subcutaneous injection are _____ and can cause _______
painful and can cause tissue damage
39
vasoconstrictors can __________ when a subcutaneous injection is given
slow absorption
40
Very rapid distribution to CNS; no drug depot (need to keep administering since rapid)
inhalation traits
41
designed for local actions
Topical
42
designed for systemic actions
transdermal (skin patch)
43
List the drug movement (3)
1. Drug
2. Membrane
3. Transport Mechanisms
44
how does drugs move through a membrane
1. lipid
2. pores
3. channels
4. transporter and carrier proteins
45
transport mechanisms for a drug (2)
1. active
2. facilitated
46
filtration transport mechanism
moves through aqueous channels
47
facilitated diffusion transport mechanism
carrier mediated transport w/o energy
48
active transport requires
energy (ATP)
49
what are the 2 types of active transporters
1. ATP binding cassette (ABC)
2. solute carrier (SLC)
50
most common route for drug transport
passive diffusion
51
movement of molecules in passive diffusion
high to low concentration
52
Passive diffusion is proportional to
- concentration gradient of the unionized drug (ionized cannot cross)
- lipid-water partition coefficient
- membrane surface area (more absorption with more SA)
- pH gradient
53
separation of water and oil in a beaker, add a drug in and some will dissolve in the oil, some in the water. The more drug placed into the liquid phase, the more lipophilic & non polar
lipid water partition coefficient
54
Drugs are weak acid/bases & exist in ionized and non-ionized forms; the percentage of the drug that exists in an ionize and non-ionized form is related to
environmental pH
55
Ability of a drug to cross a membrane is related to _________ but only related to non-ionized portions of the drug
(Ionized cannot cross the membrane)
concentration gradient
56
weak acids (HA) and weak bases (BOH) ____
Dissociate
57
what is a weak acid
anion + hydrogen ion
58
what is a weak base
cation and hydroxide ion
59
weak acids absorbed more at ___ pH
low
60
weak bases absorbed more at ___ pH
high
61
How is pH effect on drug movement measured
Henderson-Hasselbalch equation
62
According to Le Chatelier's Principle, adding additional reactant to a system or reducing concentration of any product will shift equilibrium to the ______
right
63
According to Le Chatelier's Principle, adding additional product to a system or removing reactant from system equilibrium will shift to the _______
left
64
Another term for Le Chatelier's principle is
Common Ion Effect
65
weak acids under go greater absorption in an
acidic environment
66
HA <-> H⁺ + A⁻
Increasing [H⁺] shifts equilibrium to the ________ (non-ionized form is the form that is absorbed)
left
67
Weak bases undergo greater absorption in a relatively more _______
alkaline environment
68
BOH <-> B⁺ + OH⁻
Increasing [OH⁻] shifts equilibrium to the ______ (non-ionized form is the form that is absorbed)
left
69
What is the pKa of a drug?
The pH at which the molecule is 50% ionized and 50% unionized
pH = pKa + log(A-)/(HA)
70
process by which drug absorbed in plasma gains access to sites of action
drug distribution
71
List the factors that affect drug distribution
- Blood perfusion rate
- Membrane characteristics
- Intracellular/extracellular pH
- Sequestration in fat (many drugs are highly lipophyllic)
- Protein binding (plasma and tissues)
72
what happens when a drug is sequestered in fat?
Drug cannot be metabolized or excreted so it won't be distributed quickly
73
weak acids bind to
serum albumin
74
weak base bind to
glycoprotein
75
plasma protein binding is _____
non-specific
76
Plasma protein levels change with ____ and ______
age and disease
77
consequences of plasma protein binding
- longer duration of action (less susceptible to metabolism, distribution, or excretion. Can also be a reason for toxicity due to drug displacement)
- drug-drug interactions and displacement
- misinterpretation of drug levels
78
displacement of bilirubin by sulfonamides will causes
kernicterus
79
drug distributions that are restricted by the blood brain barrier
1. drugs with low lipid/water partition coefficients
2. ionized drugs
3. protein bound drugs
80
how does the BBB limit drug distribution?
1. tight connections limit filtration
2. perivascular sheet of glial cells (thick sheet precludes all but highly lipophilic substances)
3. extensive collection of membrane transporters expel drugs
81
In order for drugs to cross the BBB, they must be _______
very lipid soluble
82
increased permeability of BBB may be caused by
inflammation
83
drugs must be ___ to cross BBB
lipid soluble
84
many drugs under 1000 MW (not many drugs are actually this big) passively diffuse across the ________ between maternal and fetal circulation
placental barrier
85
tissue layers between __________ and ________ become progressively thinner during gestation
fetal capillaries and maternal blood
86
Distribution of a drug to a baby increases as ______
term approaches
87
Apparent volume of distribution (Vd)
concentration in plasma = drug/volume
Co = D/Vd
- drug binding to tissues elevates apparent volume of distribution
- drug binding to plasma proteins depresses apparent volume of distribution
88
body volume of distribution amounts
plasma water 3L
interstitial fluid 9L
intracellular fluid 29L
total body water 41L
89
in redistribution, lipophilic drugs administered intravenously may initially distribute to...
vessel-rich organs (brain, heart, kidneys, liver, and lungs), and then redistribute to less highly vascularized tissues (muscle, skin, fat).
90
If the site of drug action is highly vascularized then redistribution serves as a
drug elimination mechanism
91
mechanism of drug elimination for highly lipophilic drugs
redistribution ex. thiopental
92
describe the increased depth of anesthesia that occurs with metabolic acidosis and thiopental
- thiopental is a weak acid, so nonionized form crosses the BBB
- metabolic acidosis increases the plasma [H+], therefore [HA] increases in plasma- more [HA - nonionized form] crosses the BBB
