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elcrs - 팜 > PHARM 4: Pharmacokinetics > Flashcards

PHARM 4: Pharmacokinetics Flashcards

1
Q

List the journey of a drug through the body:

Hint = AADMEV

A

AADMEV

  • administration
  • absorption
  • distribution
  • metabolism
  • excretion
  • voided
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2
Q

Routes of administration can be either systemic or local.

what does it mean by systemic or local?

A

SYSTEMIC = entire organism is getting exposed to the drug

LOCAL = restricted to one area of the organism

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3
Q

Routes of administration can also be enteral or parenteral.

what does it mean by enteral or parenteral?

A

ENTERAL = via GI tract

PARENTERAL = everything except the GI tract

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4
Q

What are the different methods of absorption?

A
  • through GI tract (via hepatic portal system)
  • ## inhalation (lung = well perfused)
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5
Q

Why would you administer intravenously?

A
  • provides systemic exposure very quickly
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6
Q

Drug molecules move around the body in 2 ways:
a)
b)

A

Drug molecules move around the body in 2 ways:

a) BULK FLOW TRANSFER
- in the bloodstream, it moves in bulk to the tissues

b) DIFFUSION TRANSFER
- moves molecule by molecule over short distances.

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7
Q

What are the different methods of crossing barriers?

A
  • diffuse through lipid
  • diffuse though aq pores in lipid
  • carrier molecules
  • pinocytosis
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8
Q

NOTE:
- most drugs = either weak base/acid

  • so drugs exist in ionised/non ionized form
  • ratio of ionized : non ionized depends on PH of environment + pKa of the molecules.
A

-

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9
Q

What is the

PH Partition Hypothesis?

A
  • aspirin = acidic
  • aspirin pKa = 3.4

SO

  • when aspirin enters stomach (PH1 with lower pKa compared to aspirin)
  • it becomes non ionized (non polar)
  • so it can readily diffuse across the lipid bilayer
  • into the small intestine (more basic)
  • PH of s.int is higher so aspirin becomes ionized
  • once ionised –> difficult to go through memb
  • so slower absorption in s.int than stomach
  • once it goes from liver –> systemic circulation, aspirin = in aq environment
  • so proportion of aspirin = in ionized form
  • -> ION TRAPPING
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10
Q

What are 4 factors influencing drug distribution?

A
  • Regional blood flow
  • -> better perfusion = higher drug exposure
  • -> high metabolically active tissues have more capillary density
  • Extracellular binding
  • -> if plasma protein = bound to drug (can’t be absorbed)
  • Capillary permeability
  • -> fenestrated, continuous, discontinuous
  • Localisation in tissues
  • -> drugs that are lipophilic tend to accumulate/ localize in fatty tissue
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11
Q

What are the 2 major routes of excretion?

A
  • Liver
  • -> concentrates drugs in bile + secretes into intestines
  • Kidney
  • -> converts drug into water soluble product
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12
Q

Liver tends to excrete :

Kidneys tend to excrete:

A

Liver tends to excrete :
- large molecular weight drugs

Kidneys tend to excrete:
- xenobiotics

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13
Q

Why is the majority of excreted drugs get into urine via active secretion rather than ultrafiltration?

A
  • because you can’t filter large, protein bound drug complexes.
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14
Q

describe process of excretion in kidneys

a) glomerulus
b) PCT
c) PCT/ DCT

A

a) glomerulus
- drug protein complexes not filtered

b) PCT
- active secretion of acids + bases

c) PCT/ DCT
- lipid soluble drugs

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15
Q

Why might treatment with IV sodium bicarbonate increase aspirin excretion?

A
  • IV NaHCO3 will increase urine PH
  • increase urine PH –> ionizes aspirin
  • makes it less lipid soluble
  • less aspirin = reabsorbed by tubules
  • -> increase rate of excretion
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16
Q

Describe the process of excretion by the liver

A
  • biliary excretion: concentrates large molecular weight molecules that are lipophilic
  • active transport systems: for transport of bile acids + glucuronides –> into the bile
17
Q

How might billiary excretion cause problems?

A
  • drug gets excreted into gut via bile
  • then is reabsorbed
  • taken to liver and excreted again
    (ENTEROHEPATIC RECYCLING )

–> Leads to DRUG RESISTANCE

18
Q

Define Bioavailability

A

Bioavailability = proportion of the administered drug that is available in the body to exert its pharmacological effect.

note: linked to absorption

amount of drug that gets into the systemic circulation

19
Q

Define Apparent Volume of Distribution

A

Apparent Volume of Distribution = volume in which a drug appears to be distributed.
(indicator of pattern of distribution)

note: linked to distribution

20
Q

Define Biological Half Life

A

Biological Half Life = time taken for conc of drug to fall to half its original value

note: linked to metabolism/excretion

21
Q

Define Clearance

A

Clearance = volume of plasma cleared of a drug per unit time.

note: linked to excretion

22
Q

Define First Order Kinetics

A

First Order Kinetics = rate of elimination of a drug where the amount of drug decrease at a rate proportional to the conc of drug remaining in the body

23
Q

What is First order kinetics dependent on?

A
  • conc of drug at any given time
    note:
T1/2 = Vd x 0.7/Cl 
0.7 = Log 2
24
Q

The log of conc is proportional to_____

A

The log of conc is proportional to time

25
Q

Volume of distribution =

A

Volume of distribution = dose / initial conc of drug in plasma

26
Q

What is Zero Order Kinetics?

A

Zero Order Kinetics = amount of drug decreases at a rate independent of conc of drug remaining in the body

Note: Implies a saturable (usually enzymic) metabolic process

27
Q

are antacids local/ systemic

A

-local

28
Q

are nicotine patches systemic / local?

A
  • systemic
29
Q

is betnovate local/systemic

A

-local

30
Q

note: drugs have to transverse both aqueous + lipid environment

A

-

31
Q

Why is protein bound drug not very likely to penetrate lipid memb?

A
  • because it has low bioavailability

- as it is bound to the plasma protein

elcrs - 팜 (36 decks)

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