Bps 319 - Lecture 7 Drug Absorption
Questions With Answers
small intestine The absorption takes place mainly in the ______ because of the large
surface area available for absorption in this part of the GI tract
Microvilli _____ provide more surface area for drug to absorb
Passive absorption
Active absorption Drug absorption in the small intestine can take place by:
passive absorption mechanism is passive diffusion
transcellular
paracellular
follows first-order kinetics Passive absorption can be divided into:
transcellular absorption through cell membrane
preferred by lipophilic drugs
paracellular absorption pass through gap junctions between cells
preferred by hydrophilic drugs
, active absorption occurs by active transport
Patient swallows the tablet
Tablet enters the stomach, breaks down in gastric fluid to expose/release the drug
Drug dissolves in gastric fluid
Drug passes through GI membrane
Uptake transporters - facilitates absorption
Efflux transporters - reduce absorption, can secrete drug back into the lumen
Drug-metabolizing enzymes in cell can metabolize/inactivate the drug
Drug in the capillaries, drains into hepatic artery, metabolized by the liver What are the
steps involved in oral absorption?
1. Low solubility and slow dissolution
2. Lipophilic nature of cell membrane --> limits the absorption of hydrophilic drugs
3. Variability in the gastric residence time
4. Chemical and enzymatic degradation of the drug
5. Metabolism
6. Bacterial degradation
7. P-glycoprotein drug efflux system Obstacles to drug absorption include:
Bioavailability the fraction of the dose that is reaching systemic circulation
Questions With Answers
small intestine The absorption takes place mainly in the ______ because of the large
surface area available for absorption in this part of the GI tract
Microvilli _____ provide more surface area for drug to absorb
Passive absorption
Active absorption Drug absorption in the small intestine can take place by:
passive absorption mechanism is passive diffusion
transcellular
paracellular
follows first-order kinetics Passive absorption can be divided into:
transcellular absorption through cell membrane
preferred by lipophilic drugs
paracellular absorption pass through gap junctions between cells
preferred by hydrophilic drugs
, active absorption occurs by active transport
Patient swallows the tablet
Tablet enters the stomach, breaks down in gastric fluid to expose/release the drug
Drug dissolves in gastric fluid
Drug passes through GI membrane
Uptake transporters - facilitates absorption
Efflux transporters - reduce absorption, can secrete drug back into the lumen
Drug-metabolizing enzymes in cell can metabolize/inactivate the drug
Drug in the capillaries, drains into hepatic artery, metabolized by the liver What are the
steps involved in oral absorption?
1. Low solubility and slow dissolution
2. Lipophilic nature of cell membrane --> limits the absorption of hydrophilic drugs
3. Variability in the gastric residence time
4. Chemical and enzymatic degradation of the drug
5. Metabolism
6. Bacterial degradation
7. P-glycoprotein drug efflux system Obstacles to drug absorption include:
Bioavailability the fraction of the dose that is reaching systemic circulation
