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AU 15 - Pharmacology > Pharmacokinetics - Lecture 5 > Flashcards

Pharmacokinetics - Lecture 5 Flashcards

1
Q

What are some pros of oral absorption?

A

Convenient, cheap, and fairly safe

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2
Q

What are some cons of oral absorption?

A

We have less control if we just tell a patient to take a pill

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3
Q

What are the most important sites of absorption for oral drugs and why?

A

Stomach (pH = 1.4) and Small intestine (pH = 3.0-7.0)
If a pill absorbs at a lower pH, it can spend more time in the stomach, but needs to get through quick if it is absorbed at a higher pH

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4
Q

What kind of drugs can passively diffuse through a membrane?

A

Lipophilic molecules

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5
Q

What is the partition coefficient, and why is it important?

A

[X1]/[X2] = PC

The larger the PC, the more likely a drug will be absorbed by passive diffusion
Smaller molecules are more likely to be absorbed by passive diffusion

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6
Q

What is the most important aspect affecting drugs that are acids or bases?

A

pH
Drugs with a low pKa (asprin) should be absorbed in the stomach - by the time it gets to the intestine, the higher pH will make it charged and it won’t get absorbed
Drugs with a high pKa (codeine) need to be absorbed in the intestine, because in the stomach it will charged and can’t be absorbed

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7
Q

What is the significance of facilitated diffusion to drug absorption?

A

Most small molecules can get taken up by passive diffusion, but some drugs taken orally require facilitated diffusion

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8
Q

What are the ways Active transport effects drug absorption?

A

1) ABC transporters can kick drugs out of cells when necessary
2) SLC transporters (exchange Na or K) are important for transport of certain drugs that are organic cids or bases

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9
Q

What factors affect oral absorption of drugs?

A 
pH
Surface area
Gastric emptying
Dosage form
Drug inactivation
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10
Q

How does surface area affect oral drug absorption?

A

More area = more absorption

Typically, the small intestine has the most surface area

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11
Q

What sort of drugs should be taken with food, why?

A

Acidic pills should be taken with food.
When you eat something, everything leaves the stomach in 30 min-4 hrs. Acidic pills want to spend as much time in the stomach as possible, because they’re best absorbed at low pH

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12
Q

What sort of drugs should be taken without food, why?

A

Basic pills.
When you drink water and take a pill, everything leaves your stomach in 15 min - 1 hr. Basic pills don’t want to be in the stomach long, because they’re charged in the stomach and can’t be absorbed there, so we want to get them through the stomach and to the intestines as quickly as possible

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13
Q

How does dosage form affect drug absorption?

A

Solids (pills) have to dissolve, and this can be controlled easier than some other forms

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14
Q

What are some other routes to administer drugs other than orally?

A 
Inhalation
Parenteral injection
Intravenous
Intramuscular
Subcutaneous
Topical
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15
Q

What sort of treatment is best suited for inhalation?

A

Asthma treatment

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16
Q

Profusion of the tissue is most important for what types of drug administration?

A

Intramuscular and Subcutaneous

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17
Q

What ways can drugs be distributed to tissues?

A

Capillary penetration

Entry into cells from interstitial fluid

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18
Q

Why is it difficult for drugs to get to the CNS?

A

Blood-brain barrier

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19
Q

Why are water soluble drugs slower to get to tissues than lipophilic drugs?

A

They have to go through endothelial gaps as opposed to going directly through the membrane

20
Q

What can the volume of distribution tell us?

A

IT provides an indication of how a drug is distributed, based on how much is in the plasma and how much was added
This is true if the drug is water soluble

21
Q

How many liters of plasma, interstitial space, and cells are there in the average person?

A

3 L of plasma
9 L of interstitial space
29 L cells
41 total L

22
Q

What is the equation for the volume of distribution?

A 
Q/C = Vd
Q = amount of drug administered
C = concentration of drug in the plasma
23
Q

If an administered drug never leaves the plasma, what would the Vd be?

A

3L

Q/(Q/3) = 3L

24
Q

If an administered drug goes to the plasma and interstitial space, but not into the cells, what would the Vd be?

A

12 L

Q/(Q/12) = 12L

25
Q

If an administered drug distributes to all tissues, what would the Vd be?

A

41 L

Q/(Q/41) = 41L

26
Q

What are the two phases of drug metabolism?

A

Phase I: Add (uncover) functional group

Phase II: Conjugation

27
Q

What is the most important site for drug metabolism?

A

The liver

28
Q

Microsomes

A

Membrane bound enzymes that metabolize drugs
Located on the smooth ER of hepatocytes
Microsomal enzymes are designed to remove foreign objects

29
Q

What enzymes can oxidize drugs?

A

P450 enzymes

Flavin monooxygenases

30
Q

What reduces drugs?

A

Done mostly by enteric bacteria, but sometimes by hepatocytes

31
Q

What are some things Microsomes can do to drugs?

A 
Oxidation
Reduction
Hydrolysis
Dehalogenation
Glucuronide conjugation
32
Q

Dehalogenation

A

Compounds that have halogens on them can be dangerous

However, this process can make morphine more potent

33
Q

When is non-microsomal metabolism done?

A

When the drug mimics a natural substance found in the body

34
Q

What are some non-microsomal mechanisms of drug metabolism?

A

Oxidation
Reduction
Hydrolysis
Conjugation

35
Q

What are some factors that affect drug metabolism?

A 
Entry into the liver
Enzyme inhibition
Enzyme induction
Genetics
Age
Pathology
36
Q

What are the two stages of drugs entering into the liver for metabolism?

A

k1 (movement into the liver)

k2 (metabolism)

37
Q

For most drugs, which is faster, k1 or k2?

A

k1 is slow and k2 is fast (usually)

Some transporters can heat up the process

38
Q

What does enzyme inhibition do to effect drug metabolism?

A

It slows it down

39
Q

What does enzyme induction do the effect drug metabolism?

A

Some drugs induce P450 enzymes to speed up the process of other drugs

40
Q

How does age effect drug metabolism?

A

Older people take more drugs, depening on th drugs can slow or speed metabolism

41
Q

How does pathology effect drug metabolism?

A

People who are sick will do things differently than healthy people

42
Q

What are the major components of drug excretion?

A

Glomerular filtration
Tubular reabsorption
Active transport/tubular secretion

43
Q

What is the major filter in glomerular filtration?

A

Basement membrane
It consists of glucosaminyl glycans, which are negatively charged proteins that allows or prevents things from entering the tubules of the kidney

44
Q

Tubular reabsorption

A

After things are filtered through bowman’s capsule, certain things can be reabsorbed back into the blood
Cl (passive)
Na (active)
H20 follows salt by osmosis

45
Q

Tubular secretion

A

Some things are actively pushed out from capillary endothelium into the urine
H, K, Urea, drugs

46
Q

If drugs are filtered but not reabsorbed or secreted back into the blood, how fast do they clear?

A

130 mL/min

So if the drug’s Vd is 12 L, the drug will have a t1/2 of about an hour

47
Q

If drugs are actively secreted and not reabsorbed, how fast do they clear?

A

650 mL/min

So if the drug’s Vd is 12L, they drug will have a t1/2 of about 13 min

AU 15 - Pharmacology (6 decks)

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