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PT 1 > L2 Pharmacokinetics I: Absorption and Distribution > Flashcards

L2 Pharmacokinetics I: Absorption and Distribution Flashcards

1
Q

___ is the time course of drug action as it relates to the concentration of the drug in the plasma.

A

Pharmacokinetics

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2
Q

What are the four major aspects of pharmacokinetics?

A

ADME:

  1. Absorption
  2. Distribution
  3. Metabolism
  4. Excretion
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3
Q

With respect to the time course of plasma drug concentration, when does the onset occur?

A

The onset occurs when the drug reaches the minimum effective concentration.

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4
Q

With respect to the time course of plasma drug concentration, what is the duration?

A

The time from onset to the time the drug drops below the minimum effective concentration

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5
Q

With respect to the time course of plasma drug concentration, what is the intensity?

A

The concentration between the minimum effective concentration and the maximum concentration reached

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6
Q

With respect to the time course of plasma drug concentration, what is the therapeutic range?

A

Maximum tolerated concentration to minimum effective concentration

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7
Q

AUC = ? (for i.v.)

A

Dose (i.v.) / CL

CL = clearance

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8
Q

AUC = ? (for p.o.)

A

DOSE (p.o.) / (CL/F)

CL = clearance
F = bioavailability
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9
Q

What are the two major uses of the AUC?

A
  1. Compare amount of drug that reaches the systemic circulation by different routes of administration (bioavailability)
  2. Compare clearance of a drug in different individuals after administration of the same dose
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10
Q

F = ?

A

AUC oral/AUC i.v. (%)

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11
Q

CLx/CLy = ?

A

AUCy/AUCx

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12
Q

What is the process by which drugs move from their site of administration to the plasma?

A

Drug absorption

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13
Q

What are some factors that affect drug absorption?

A
  1. Chemical composition of drug and delivery formulation
  2. Regional differences in blood flow
  3. Transport mechanisms
  4. Permeability characteristics
  5. Ion-trapping
  6. Non-specific binding
  7. Surface area
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14
Q

Lipid solubility is affected by the degree of ___.

A

Ionization

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15
Q

pKa = ?

A

Acids: pH + log[AH]/[A-]
bases: pH + log [BH+]/[B}

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16
Q

Weak acids are non-ionized most in ___ environments such as the ___; weak bases are non-ionized most in ___ environments such as the ___.

A

Acidic; stomach; basic; small intestine

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17
Q

What is the main site of absorption of most orally administered drugs and why?

A

Small intestine; much larger surface area than the stomach.

18
Q

What are the three major processes that reduce bioavailability?

A
  1. First-pass metabolism
  2. Secretion into bile and reabsorption into the intestine
  3. Incomplete absorption
19
Q

What is the fraction (F) of the administered dose that reaches the systemic circulation in its active form?

A

Bioavailability

20
Q

F oral = ?

A

AUC p.o. / AUC i.v.

21
Q

Dose p.o. = ?

A

Dose i.v. / F oral

22
Q

What is the salt factor (S)?

A

The fraction of the total drug that will be delivered as active drug to the systemic circulation when a fraction of the total weight is inactive salt

23
Q

What must be adjusted by the salt factor to achieve a specific target concentration of the active drug?

A

Loading or maintenance doses (multiply F by S)

24
Q

What are the advantages and disadvantages to sublingual and buccal drug administration?

A

Advantages: avoids first pass metabolism, higher pH better for absorption of basic drugs

Disadvantages: taste and discomfort

25
Q

What are the advantages and disadvantages to rectal drug administration?

A

Advantages: 50-60% of absorbed drug bypasses first pass; useful in cases of nausea and vomiting
Disadvantages: discomfort, inconvenience

26
Q

Drug absorption via inhalation varies based on what two factors?

A

Depth and duration of inspiration

27
Q

What are the advantages and disadvantages to parenteral drug administration?

A

Advantages: greater degree of reliability and precision of administered dose, fewer problems with absorption

Disadvantages: sight of the needle, pain, tissue damage/irritation, drugs must be in solution, limited volume

28
Q

What are the advantages and disadvantages to subcutaneous parenteral drug administration?

A

Advantages: slow, even absorption; depot; rate may be modified by altered blood flow

Disadvantages: not effective when peripheral circulation is impaired, limited volume

29
Q

What are the advantages and disadvantages to intramuscular parenteral drug administration?

A

Advantages: more rapid absorption than subcutaneous, rate may be modified

Disadvantages: risk for infection and nerve damage, risk of inadvertent i.v. administration

30
Q

What are the advantages and disadvantages to intravenous parenteral drug administration?

A

Advantages: fastest and most reliable

Disadvantages: risk of overdose by bolus effect

31
Q

What factors affect distribution of absorbed drugs?

A
  1. Regional differences in blood flow
  2. Tissue mass
  3. Transport mechanisms
  4. Permeability characteristics
  5. Ion-trapping
  6. Protein binding
32
Q

___ binds acidic drugs; ___ binds basic drugs.

A

Albumin; alpha-1 acid glycoprotein

33
Q

What happens to protein-bound drugs?

A

They stay in the plasma

34
Q

What is volume of distribution (Vd)?

A

A measure of how evenly distributed a drug is in the body; the theoretical volume of fluid in which the total drug administered would have to be diluted to produce the concentration in plasma

35
Q

Vd = ?

A

Dose/C0 (concentration at time = 0)

Vp + [Vt * (fraction unbound in plasma/fraction unbound in tissue)]

36
Q

An increase in the unbound fraction of total [drug] will result in an increase in ___.

A

The apparent volume of distribution (Vd)

37
Q

What are the major compartments of the body in which drug distribution occurs?

A
  1. Plasma (5%)
  2. Interstitial fluid (16%)
  3. Intracellular fluid (35%)
  4. Transcellular fluid (2%)
  5. Fat (20%)
38
Q

What type of drugs may reach all compartments?

A

Lipid-soluble drugs

39
Q

What three things can act as drug reservoirs?

A
  1. Fat
  2. Muscle
  3. Plasma proteins
40
Q

___ may compete for protein binding and increase the unbound fraction of other drugs.

A

Sulfonamides

PT 1 (34 decks)

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