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Pharmacology > Intro 2 Pharmacokinetics > Flashcards

Intro 2 Pharmacokinetics Flashcards

1
Q

Define Pharmacology

A

study of interactions of chemicals within living systems

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2
Q

Define Medical pharmacology

A

science of substances used to prevent, diagnose, and treat disease

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3
Q

Define Drug

A

any substance that brings about a change in biologic function through its chemical actions

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4
Q

Define Receptor

A

the molecular components of the body with which a drug interacts to bring about its effects

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5
Q

a) What are the 3 types of receptor bonds and b) name an example of each?

A
  • Covalent, Electrostsatic, and Other
  • Covalent bonds: very strong, usually irreversible
  • Electrostatic bonds: weaker bonds
  • Other bonds (very weak): hydrogen bonding, etc.
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6
Q

Define Pharmacokinetics

A

Actions of the body on a drug

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7
Q

What are the 4 actions of the body on a drug?

A

Absorption, Distribution, Metabolism, and Elimination

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8
Q

Define Pharmacodynamics

A

Actions of the body on a drug

what reaction specific drugs have on the body

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9
Q

What are the major routes of administration for medications and describe each.

A

Parenteral, Enteral, and Other

  • Parenteral: Doesn’t utalize GI
  • Enteral: Utalizes GI
  • Other
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10
Q

Name the 3 major Parenteral routes

A

IV, IM, and SC

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11
Q

What are the advantages of Parenteral administration (IV, IM, SC)?

A
  • Rapid onset of action
  • avoidance of harsh GI envt
  • can be utilized in unconscious
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12
Q

What are the disadvantages of Parenteral administration (IV, IM, SC)

A
  • Overdoses can’t be as readily treated
  • pain/fear associated w/ administration
  • higher infection risk
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13
Q

What are the risks associated with IV injection?

A
  • Infections through contamination at injection site
  • Hemolysis
  • Pain/injection site reaction
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14
Q

Describe the absorption of IM administration

A
  • Requires absorption from site of administration by avoids GI tract & 1st pass
  • Drugs in aqueous solutions–> rapid absorption
  • Depot formulations (non-aqueous)–> slow absorption/sustained release
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15
Q

Describe SQ administration

A
  • requires absorption from administration site
  • slower than IV
  • minimizes some risks associated with IV administration
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16
Q

What are the advantages of Oral (PO) administration?

A
  • Easy to administer
  • Minimizes risk of systemic infections
  • Overdoses can potentially be treated
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17
Q

What are the disadvantages of PO administration?

A
  • Complicated drug absorption pathways with 1st pass effect
  • Acidic GI envirnoment
  • Absorption is influenced by food intake or other drugs
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18
Q

Describe Sublingual (SL) administration

A

Placement of drug under tongue, which allows for direct diffusion into systemic circulation

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19
Q

What are the advantages of SL administration?

A
  • Convenient administration -rapid absorption
  • low risk of infection
  • Avoidance of harsh GI environment & 1st pass effect
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20
Q

What are the advantages of Rectal (PR) administration?

A
  • Prevents destruction of drugs by harsh GI
  • Lower rates of biotransformation from the liver than PO
  • Useful in emesis (vomiting)
  • Useful in unconsciousness or actively seizing pts.
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21
Q

What are the disadvantages of PR administration

A
  • Discomfort
  • Drugs can cause irritation/inflammation of rectal mucosa
  • Absorption greatly varies
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22
Q

Describe inhalation administration

A
  • Effective for respiratory conditions due to direct delivery to the site of action
  • delivery to large surface
  • used for gases
  • minimization of systemic side effects
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23
Q

Describe intranasal administration

A

Absorbed for local effects or systemic effects

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24
Q

Describe intrathecala administration (space under membrane of brain or sc)

A
  • Direct administration into CSF

- Useful in treating meningitis

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25
Q

Describe topical administration

A
  • Mostly reserved for local effects of drugs

- Applied to skin, eyes, etc.

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26
Q

Describe transdermal administration (ex patch)

A
  • Systemic effect by application of drug to the skin
  • Varying rate of absorption based on skin condition at the site of application
  • used for sustained delivery of drugs
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27
Q

Define absorption

A

The transfer of a drug from its site of administration to the blood stream

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28
Q

Name the factors that affect absorption

A 
Solubility
Concentration
Blood flow
Surface area
Contact time
pH
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29
Q

Name the mechanisms of absorption

A

Passive diffusion, Facilitated diffusion, active transport, and endocytosis

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30
Q

Describe how concentration affects absorption

A

High concentrations of a drug lead to more absorption than low concentrations of a drug

31
Q

Describe how blood flow affects absorption

A

Greater blood flow leads to higher rates of absorption

32
Q

Describe how surface area affects absorption

A

More surface area for absorption leads to more rapid absorption (ie. lungs, intestine)

33
Q

Describe how contact time affects absorption

A

The greater the contact time, the greater the absorption

34
Q

Describe how pH affects absorption

A

pH directly determines the amount of ionized vs. unionized (which affects solubility)
-only ionized (no charge) forms can cross cell membranes

35
Q

What donates a proton to form anions?

A

Weak acids

36
Q

What accepts a proton to form cations?

A

Weak bases

37
Q

What is the Henderson-Hasselbalch used to determine?

A

The ratio of ionized to unionized

38
Q

How is a pka value linked to an acid?

A

The lower the pKavalue, the stronger the acid

39
Q

Define Bioavaliability (F)

A

Fraction of unchanged drug reaching the systemic circulation following administration

40
Q

What is the bioavaliability (f) of an IV injection?

A

100%

41
Q

What does the bioavaliability of an PO medication depend on?

A

Absorption (rate/extent) and Metabolism (1st pass effect)

42
Q

Describe the 1st pass effect

A
  • After absorption, portal blood takes the drug to the liver before entering the circulation
  • When passing through the liver, the drug may be metabolized/inactivated, or excreted into bile–> less active drug makes it to systemic circulation
43
Q

What formula is used to determine bioavaliability?

A

F = f x (1-ER)

(f)=extent of absorption (ER)=extraction ratio .

44
Q

Define distribution

A

Delivery of a drug from the systemic circulation to target tissues

45
Q

What are the major determinants of drug distribution?

A
  • Blood flow
  • Capillary permeability & Blood brain barrier
  • Drug structure,properties/ characteristics
  • Protein binding
46
Q

How does blood flow affect distribution?

A

Greater blood flow leads to faster distribution of drug

47
Q

Name high flow and low flow areas of distribution in the body

A

(high flow) brain, liver, kidney

(low flow) adipose tissue

48
Q

Define capillary permeability

A

Capacity for drug molecules to pass through capillary walls

49
Q

What type of capillary permeability does the Brain have?

A

continuous capillary structure (does not allow drugs through)

50
Q

Describe the mechanisms of the BBB

A

(Lipid soluble)
-Dissolve in membrane of endothelial cells
(Specific transporters)
-Carry the drug through the membrane of endothelial cells

51
Q

Left off on distribution factors slide 33; also revisit question 7: Describe transport mechanisms of a drug from the site of administration to the site of action.

A

go back

52
Q

Define volume of distribution (Vd)

A

Distribution of drug within the fluid compartments of the body
(tells how much blood is in the body as opposed to the blood)

53
Q

*How much body water is located intracellularly?

A

2/3

54
Q

*How much body water is located extracellularly?

A

1/3

55
Q

*How much body water is located intravascular (IV)?

A

1/4

56
Q

*How much body water is located interstitial (IS)?

A

3/4

57
Q

What percentage of the body is composed of water?

A

60%

58
Q
  • What formula is used to calculate volume of distribution?
A

Vd = D/ C

  • D: total amount of drug in body
  • C: plasma concentration of drug
59
Q

*What does a small Vd indicate?

A

The drug is primarily in the plasma

60
Q

*What does a high Vd indicate?

A

A high concentration of a drug in the extravascular space (in tissues)

61
Q
  • What formula would you use to approximate how much drug is needed to achieve the appropriate concentration level based on current plasma level?
A

(Vd) (C2-C1)

  • C1 = Current plasma concentration
  • C2 = Desired plasma concentration
62
Q

What occurs when a protein binds to a drug?

A

The protein renders the bound drug inactive

63
Q
  • What type of protein binding is reversible?
A

Binding to albumin

64
Q
  • What occurs in protein binding competition?
A

2 different drugs have a high affinity for abumin and they compete for the binding site

65
Q
  • You have a patient who is currently taking a drug (D1) that is protein bound. Another protein-bound drug is added (D2). What will occur?
A
  • D1 will be displaced from binding sites by D2
  • Toxicity may occur with D1 since the displaced drug (D1) has become activitated
  • Toxicity may occur with D2 since there is a higher fraction of free drug and no available binding sites
66
Q

*You have a patient who is taking D1 and D2 (both protein bound). What will happen if D1 is discontinued?

A
  • Once D1 is eliminated, D2 will have more avaliable protein binding sites
  • D2 will become protein bound, and thus inactive
  • Sub-therapeutic levels of D2 may occur
67
Q

What occurs during distribution?

A

The drug may initially be distributed to one area and then redistributed to another

68
Q

How might inflamed meninges alter distribution?

A

They may increase the distribution of drugs in the CSF with meningitis

69
Q

What affect might inflammation/infection have on distribution?

A
  • A layer of WBC and fluid from edema may lead to decreased drug distribution to infected area
  • inflammation may increase blood flow due to inflammatory response and increased distribution to the affected tissues
70
Q

*Which route of administration typically has the quickest onset of action (effect)?

A

Intravenous

71
Q

*What route of administration is LEAST desirable for a drug that is not stable in an acidic environment?

A

Oral

72
Q

*What mechanism of absorption is capable of moving drugs against a concentration gradient?

A

Active Transport

73
Q

*A patient taking two highly protein-bound drugs abruptly stops taking one of them. The therapeutic effect of the continued drug would be expected to

A

Decrease (because the drug is now available for binding to a protein; if the drug binds to a protein it would become inactive and decrease the therapeutic effects)

74
Q

*Estimate the oral bioavailability of a drug that is 100% absorbed and has an extraction ratio of 0.25

A

F =f x (1-ER) = 100 x (1-25)=

75%

Pharmacology (5 decks)

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