3 Absorption and Distribution Flashcards

1
Q

What two factors affect area under the curve?

A

bioavailability of the drug

clearance rate of the person

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2
Q

Clearance is inversely related to what?

A

area under the curve

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3
Q

What is drug absorption?

A

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

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4
Q

What factors affect drug absorption?

A
  1. chemical composition and delivery of drug
  2. regional differences in blood flow
  3. transport mechanisms
  4. permeability characteristics (lipid solubility)
  5. ion-trapping
  6. nonspecific binding
  7. surface area
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5
Q

What is aqueous diffusion?

A

small molecules

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6
Q

What is lipid diffusion?

A
  • passive process
  • driven by concentration gradient
  • rate of absorption increases with increasing drug concentration
  • the more lipid soluble the faster the rate of transport
  • if too lipid soluble may not be soluble in aqueous gut fluid and this limits absorption
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7
Q

When acids or bases are protonated are they charged? Is the ionized form more soluble or less lipid soluble?

A

acids protonated= uncharged (acidic env good)
bases protonated= charged
(basic env good)

ionized=less lipid soluble

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8
Q

Degree of ionization depends on what?

A

difference between pH and pKa

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9
Q

Where is the main site of drug absorption?

A

stomach

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10
Q

What type of metabolism is oral administration? How is this affected by enterohepatic circulation?

A

first pass: pass through liver, only a fraction of drug reaches system circulation (bioavailability, F)
Enterohepatic circulation: drugs may be secreted into the bile and reabsorbed via instentine-can delay delivery to systemic circulation and reduce bioavailability

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11
Q

What is the salt factor?

A

the fraction of total drug that will be delivered as active drug to the systemic circulation ( like bioavailability)

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12
Q

What are the advantages to sublingual(similar to buccal)?

A
  • bypass portal circulation and avoid first pass metabolism

- higher pH may be beneficial for absorption of more basic drugs

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13
Q

What are the advantages to rectal?

A

50-60% of absorbed drug by-passes portal circulation and therefore avoids first pass metabolism
-useful in cases of nausea and vomiting

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14
Q

How are inhaled drugs absorbed?

A

passive diffusion and is facilitated by large surface area

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15
Q

How are transdermal drugs absorbed? WHat are the benefits? COns?

A

passive diffusion across skin driven by concentration gradient
Pros
-controlled release of drug-steady blood-level profile
-user friendly
-bypass GI

Con
-skin barrier limits the number of drugs that can be delivered

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16
Q

How does blood flow affect IV drug administration? What are the pros of parterenteral?

A
  • blood flow to the area maintains the concentration gradient
  • drug absorption is faster in highly vascularized tissue such as skeletal muscle

Pro

  • greater degree of reliability and precision
  • fewer problems with absorption
17
Q

WHat are disadvantages of parenteral?

A
  • tissue damage and irritation
  • drug must be in solution
  • limited volume
18
Q

What are the factors that affect distribution?

A
  1. regional differences in blood flow
  2. tissue mass
  3. transport mechanics
  4. permeability characteristics
  5. ion trapping
  6. protein binding
19
Q

What does albumin bind to?

A

acidic drugs

20
Q

What does alpha 1 acid glycoprotein bind to?

A

basic drugs

21
Q

What is one compartment distribution?

A

rapid equilibrium is achieved between plasma and tissue distribution following drug administration
-plasma concentration-time profile declines mono-exponentially

22
Q

What is two compartment distribution?

A

rapid distribution to a central compartment(plasma) is followed by slow distribution to other tissues/binding sites.
-bi-exponential plasma concentration-time profile

23
Q

What is volume of distribution?

A

how evenly distributed a drug is in the body

24
Q

What is Vd?

A

theoretical volume of fluid into which the total drug administered would have to be diluted to produce the concentration in the plasma

25
What can serve as drug reservoirs?
fat and muscle and plasma proteins (sulfonamides compete)