2: Absorption routes

Question 1

What are the types of drug administration?

Answer 1

• oral
• inhalation
• rectal
• topical
• parenteral (injections)

Question 2

Local versus systemic

Answer 2

Local - will not leave local area (drug wouldn’t reach plasma)
systemic - drug will go into circulation and go into the blood to distribute into other organs (you would use plasma concentrations to find drug concentration)

Question 3

Steps of oral (PO)

Answer 3

1. mouth
2. stomach (pH 1-3) - gastric fluids are low (when you take food, pH increases to 4-5 and can change the drug profile)
3. disintegration - larger piece disintegrated into small parts to smaller
4. dissolution - the drug is able to dissolve in solution
5. Drug solution goes through gastric emptying and enters the small intestine
6. the drug is in solution and is able to be absorbed and enters the liver through the hepatic vein
7. after the liver, the drug will enter systemic circulation

Question 4

(true/false) There is a grace period between absorption and circulation where you can correct wrong dosage.

Answer 4

True

Question 5

Explain First Pass Metabolism

Answer 5

A drug is administered by mouth and is absorbed from the GI tract and is transported to the liver via the portal vein. Only a small amount of the drug actually reaches circulation and its intended target tissue.

Question 6

Oral: pros and cons

Answer 6

Pros: convenient, cheaper, variety of dosage forms available
cons: first-pass effect, food and GI motility can affect drug absorption, local effect, you also do not know 100% if the patient is taking the right dose.

Question 7

Buccal and sublingual: pros and cons

Answer 7

pros: bypass first-pass effect (more drug in circulation), rapid absorption, drug stability bc of stable mouth pH
cons: inconvenient to have in mouth, better for small doses, bad drug taste

Question 8

rectal (suppository or enema): pros and cons

Answer 8

pros: reduced first-pass effect, useful for special patients that cannot take other forms of the drug
cons: incomplete absorption (not enough liquid to dissolve the drug), not well accepted by the body

Question 9

Where in the GI tract are most drugs absorbed following oral administration?

Answer 9

Small intestine!

Question 10

subcutaneous: pros and cons

Answer 10

pros: can be self-administered by patient, complete absorption
cons: can be painful, small doses

Question 11

Intramuscular: pros and cons

Answer 11

pros: larger volume than SC, a sustained release effect
cons: trained personnel, absorption is erratic, painful

Question 12

topical vs. transdermal

Answer 12

topical - local effect (ear drops, eye drops, sunscreens)
transdermal - nitroglycerin ointment (molecules of the drug must go through skin layer

Question 13

Bioavailability

Answer 13

The fraction of an administered dose that reaches systemic circulation.
Fpo=po/iv (IV bioavailability = 100)