PCEUT 531 Set Exam
Tested Questions & Reviewed Correct
Detailed Answers
New Update Study Material!!
1. What is drug absorption influenced by? - ANSWER
-dissolution in GI fluids
-permeability across GI mucosa
-transit through GI tract
Steps in drug absorption - ANSWER
disintegration --> dissolution --> permeation
2. Permeability limited absorption - ANSWER
drugs with high solubility BUT low permeability (low LogP)
- ANSWER rate of absorption is constrained by passage thru GI mucosa
dissolution limited absorption
drugs with high permeability BUT low solubility (high LogP)
- ANSWER Absorption depends on rate of dissolution in GI fluids
3. What is the optimal logP for permeability?
LogP between 1-3
,4. What must drugs exhibit for dissolution? GI absorption?
- dissolution: drugs must exhibit hydrophilicity
- GI absorption: drugs must exhibit lipophilicity
noyes-whitney dissolution model
5. Factors affecting dissolution rate: - ANSWER
-particle size
-solubility
-pH
-agitation
-viscosity
-temperature
GI pH variation
stomach: 1-3, 2-5 when buffered by food
small intestine: 5-7
large intestine: 7-8
WA/WB absorption in stomach
WA: good absorption (non-ionized form)
WB: poor absorption (ionized form)
WA/WB absorption in small intestine
WA: better absorption due to large surface area (EVEN if ionized)
WB: good absorption (non-ionized form)
transport mechanisms across GI membrane
, passive diffusion: along concentration gradient, Fick's law
active transport: requires energy and carrier proteins
efflux transporters: proteins pump drugs back into GI lumen --> reduces
absorption
5. Why is the small intestine the primary site of drug absorption for WA, even if its
ionized? - ANSWER
-VERY large surface area
-even if there is ionization, it does NOT restrict permeation of a lipophilic drug
since ionic equilibrium is reversible; as a small amount of non-ionized drug is
absorbed, the ionized drug reassociates with H+ to form more non-ionized drug,
allowing further absorption
not all drugs are suitable for extended release formulations. explain
ER is not suitable for permeation limited absorption drugs because it would slow
down the absorption even more
intramuscular (IM)
advantages:
-poor oral availability drugs
-emergency situations
-prolonged effects
-high blood flow in muscle
disadvantages:
-pain at injection site
-risk of infection
-slower than IV
when to use:
-when PO not viable
-prolonged effect
Tested Questions & Reviewed Correct
Detailed Answers
New Update Study Material!!
1. What is drug absorption influenced by? - ANSWER
-dissolution in GI fluids
-permeability across GI mucosa
-transit through GI tract
Steps in drug absorption - ANSWER
disintegration --> dissolution --> permeation
2. Permeability limited absorption - ANSWER
drugs with high solubility BUT low permeability (low LogP)
- ANSWER rate of absorption is constrained by passage thru GI mucosa
dissolution limited absorption
drugs with high permeability BUT low solubility (high LogP)
- ANSWER Absorption depends on rate of dissolution in GI fluids
3. What is the optimal logP for permeability?
LogP between 1-3
,4. What must drugs exhibit for dissolution? GI absorption?
- dissolution: drugs must exhibit hydrophilicity
- GI absorption: drugs must exhibit lipophilicity
noyes-whitney dissolution model
5. Factors affecting dissolution rate: - ANSWER
-particle size
-solubility
-pH
-agitation
-viscosity
-temperature
GI pH variation
stomach: 1-3, 2-5 when buffered by food
small intestine: 5-7
large intestine: 7-8
WA/WB absorption in stomach
WA: good absorption (non-ionized form)
WB: poor absorption (ionized form)
WA/WB absorption in small intestine
WA: better absorption due to large surface area (EVEN if ionized)
WB: good absorption (non-ionized form)
transport mechanisms across GI membrane
, passive diffusion: along concentration gradient, Fick's law
active transport: requires energy and carrier proteins
efflux transporters: proteins pump drugs back into GI lumen --> reduces
absorption
5. Why is the small intestine the primary site of drug absorption for WA, even if its
ionized? - ANSWER
-VERY large surface area
-even if there is ionization, it does NOT restrict permeation of a lipophilic drug
since ionic equilibrium is reversible; as a small amount of non-ionized drug is
absorbed, the ionized drug reassociates with H+ to form more non-ionized drug,
allowing further absorption
not all drugs are suitable for extended release formulations. explain
ER is not suitable for permeation limited absorption drugs because it would slow
down the absorption even more
intramuscular (IM)
advantages:
-poor oral availability drugs
-emergency situations
-prolonged effects
-high blood flow in muscle
disadvantages:
-pain at injection site
-risk of infection
-slower than IV
when to use:
-when PO not viable
-prolonged effect
