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Pharmacokinetics > Oral Absorption > Flashcards

Oral Absorption Flashcards

1
Q

What are the 3 definitions of absorption?

A
  1. Absorption occurs when drug reaches the systemic circulation
  2. When drug reaches the portal veins blood stream
  3. Drug is assumed to be absorbed when it leaves the lumen and crosses the apical membrane of the enterocytes lining the intestine
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2
Q

What are the factors that affect drug absorption?

A
  1. Physiochemical properties of drug and environment of small intestine
  2. Dosage form
  3. Anatomy and physiology of absorption site
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3
Q

What are the properties of the absorption site an can effect drug absorption?

A
  1. SA or GIT
  2. Stomach emptying rate
  3. GI motility
  4. Blood flow to absorption site
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4
Q

What are the studies of absorption kinetics?

A
  1. Top-down
  2. Bottom-up
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5
Q

What is the difference between top-down and bottom-up?

A

TD: Based on observed clinical data
BU: Based on the broader understanding of the human body and its mechanism

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6
Q

What is the top-down approach?

A
  1. Based on compartmental models
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7
Q

What is the bottom-up approach?

A
  1. Small elements of system are defined in great detail
  2. Smaller elements are combined into subsystems, and systems to describe overall process
  3. More complicated approach with many variables
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8
Q

What is the goal of top-down and bottom-up methods?

A

To make plausible physiologic predictions

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9
Q

Describe the PK of drug absorption?

A
  1. Can be 1st or 0
  2. Rate of drug amount is dependent of rates of elimination and absorption
  3. Net rate of drug accumulation is body is equal to the rate of absorption less than elimination regardless of 0 or 1st order
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10
Q

What is the equation for PK drug absorption?

A
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11
Q

What is the absorption phase?

A
  1. Rate of drug absorption is greater than the rate of drug elimination
  2. Elimination phase still occurring during absorption phase
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12
Q

What is the peak-drug concentration?

A
  1. Rate of drug absorption equals the rate of drug elimination
  2. No net change in the amount of drug in the body
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13
Q

What is post-absorption phase?

A
  1. Immediately after peak drug absorption
  2. Some drug is still absorbed
  3. Rate of drug elimination is faster than rate of absorption
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14
Q

What is the elimination phase?

A
  1. Drug at the absorption site becomes deplete
  2. The rate of drug absorption approaches 0
  3. Curve represents elimination only
  4. First order
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15
Q

Identify the phases of drug absorption

A

A: Absoprtion
B: Peak drug concentration
C: Post absorption
D: Elimination

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16
Q

What is are the factors that effect the rate of absorption?

A
  1. Drug dissolution
  2. GI motility
  3. Blood flow
  4. Drug transport across membranes
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17
Q

What is the difference between o and 1st order absorption?

A

0: controlled release products or saturable absorption processes
1: Immediate release products

18
Q

What is ka useful for?

A

Designing multiple dose regimens

19
Q

What is k and ka useful for?

A

Determining peak and trough concentration in multiple dosing

20
Q

What is the equation associated with 0-order input, 1st order output

21
Q

What equation describes 1st order absorption (just absorption)?

22
Q

What equation describes 1st order absorption (just elimination)?

23
Q

What is equation that describe both 1st order absorption and elimination?

24
Q

What is tax?

A

Time to reach peak concentration

25
What is Cmax?
Peak concentration following a single dose
26
What factors is tmax independent and dependent on?
I: Dose D: rate constant for ka and k
27
Identify the properties of Cmax?
1. Rate of drug absorbed is equal to the rate of drug eliminated. 2. Net rate of concentration change is equal to zero 3. Directly proportional to Dose and F.
28
How do we find tmax?
29
How do we find Cmax?
30
What are the intercept methods to find k?
1. Plasma concentration 2. Amount excreted in urine
31
What is the equation for the elimination phase?
32
How do we get k?
Find in by the elimination phase slope
33
What is ka negative?
Drug is leaving the GIT and eliminating into body
34
What is lag time?
The time delay prior to the commencement of first-order drug absorption
35
What might cause lag in absoprtion?
1. Changes in Gi motility 2. Opiods 3. Metoclopramide 4. Natural aging: constipation
36
When would a flip-flop or k and ka occur?
Drugs with fast elimination (k>ka)
37
What are the effects of Ka on Cmax,Tmax, AUC?
Increased Ka: Decrease tmax, Increase Cmax, AUC unchanged
38
Effects of K on Cmax, Tmax, and AUC?
Increased K: Decreased tmax, Cmax, AUC
39
What are the effects of flip-flop Ka>K?
Increase ka and decreased k: tmax unchanged, increase Cmax and AUC
40
What is Wagner-Nelson used for?
1COM model
41
What is Loo-Riegleman used for?
2COM model

Pharmacokinetics (29 decks)

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