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PHARMACOLOGY - Antiviral, Classic Chemo, ADME > ADME 1 > Flashcards

ADME 1 Flashcards

1
Q

What are the boundaries of the therapeutic window?

A

Maxima:
- Minimum Toxic Concentration/ Maximum Tolerable Concentration

Minima:
- Minimum Effective Concentration

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2
Q

What is the Therapeutic index?

A

Therapeutic Index = Minimum Toxic Conc. (for 50%)/Minimum Effective Conc. (for 50%)

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3
Q

See Graph for differences in getting into the therapeutic window for IV and Oral administration methods.

A

See Graph for differences in getting into the therapeutic window for IV and Oral administration methods.

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4
Q

What is the principle concern of pharmacokinetics?

A

The Fate of the Drug in the body

  • How does it get in
  • Where does it go
  • what changes are made to it
  • how does it get out
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5
Q

What determines the pharmacokinetics of a drug?

- what do the factors govern?

A
  • Absorption
  • Distribution
  • Metabolism
  • Excretion
    (ADME)

These govern:

  • Onset
  • Intensity
  • Duration of drug action
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6
Q

What is the relationship between absorption, metabolism and excretion during the rising and falling phase of a drug?

A

Rising Phase:
Abs. > Metabolism and Excretion

Falling Phase:
Metabolism and Excretion > Abs.

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7
Q

Determine the following for a lipid membrane:

  • water permeable?
  • Size of Drug that can pass through?
  • Permability to peptides?
  • What passes through best?
A
  1. Yes, its water permeable, small polar uncharged particles can cross
  2. Low MW (100-200 Da) drugs can pass through pores
  3. Relatively impermeable to proteins and peptides
  4. Lipophilic and Non-polar and non-ionized compounds may pass through the membrane
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8
Q

What methods do most drugs used to cross membranes?

A

Passive Diffusion

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9
Q

What is Fick’s Law?

- what do each of the variables mean?

A

Diffusion Rate = -DAK(Cin-Cout)/∆x

D - Diffusion coefficient (inverse proportion to size)
A - Surface area
K - Solubility of the Drug (affects by ionization and thus pH)
∆x - membrane thickness

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10
Q

What methods do large and/or polar molecules use to get across lipid membranes?

A

They must be carried by Carrier-Mediated Biotransport

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11
Q

T or F: the electrochemical gradient dictates the direction of movement of molecules transported by Carrier-Mediated Biotransport.

A

True, drugs carried by this method CANNOT go against their biochemical Gradient

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12
Q

Determine which if the following applies to facilitated diffusion, active transport, or both?

  • Movement against Concentration Gradient
  • Utilization of Energy
  • Saturation Kinetics
A

Facilitated Diffusion:

  • CANNOT move against gradient
  • DOES NOT use energy
  • YES, it DOES display saturation kinetics

Active Transport:

  • Yes, it can move against gradient
  • Yes, it requires energy
  • Yes, is displays saturation kinetics
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13
Q

How do riboflavin and B12 cross membranes?

A

Via Facilitated Diffusion

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14
Q

How does 5-flurouracil cross membranes?

A

Active transport

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15
Q

Don’t for get about co-transport and counter-transport.

A

Don’t for get about co-transport and counter-transport.

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16
Q

What does P-glycoprotein act on?

A

Its an MDR pump that pumps out chemotherapeutic agents

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17
Q

How are vitamins A, D, E, and K taken up?

A

Pinocytosis

**This can be clathrin dependent or independent

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18
Q

What are the two requirements for a drug to get into and out of a lipid membrane?

A

Must be soluble in the membrane

Must be soluble in the AQUEOUS phase to get out of the membrane

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19
Q

What is the pH-partition theory?

A

Says that pH and pka determine if a drug will be charged in a given environment, if that molecule neutral at a time, it will be much more likely to cross the lipid membrane.

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20
Q

What is the driving force for a drug across the membrane?

A

**the concentration gradient that exist for the NONionized form.

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21
Q

What is the Henderson Hasselbach equation for acids and for bases?

A

Acids:
- pH = pKa + log[A-]/[HA]

Bases:
- pH = pKa + log [B]/[BH+]

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22
Q

What is the implication of most drugs being weak electrolytes?

A

Ion trapping can occur - acidic drugs will be neutral in an acidic environment, and they can move across the membrane into a more basic environment. When they move into the basic environment they get trapped because they become charged and can no longer cross the membrane

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23
Q

If there is an acidic and basic side to a membrane, which side will basic drugs get trapped on?

A

The acidic side

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24
Q

Define absorption.

A

The RATE at which a drug leaves its entry point and the EXTENT to which that occurs

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25
Q

What is bioavailability and what is the range of bioavailability?

A

Bioavailability - a range from 0 to 1 to describing the fraction of drug that reaches its site of action or a biological compartment to where is can reach its site of action.

  • IV drugs are naturally 1
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26
Q

What are the two general ways in which a medicine can be adiministered?

A

Enteral (by GI tract) and Parenteral (not by GI tract)

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27
Q

What are the Enteral Routes of Administration?

A
  1. Oral
  2. Sublingual
  3. Rectal
28
Q

What are the Parenteral Routes of Administration?

A
  1. Intravenous (IV)
  2. Subcutaneous
  3. Intramuscular
  4. Intraarterial
  5. Inhalation
  6. Topical
29
Q

For drugs that have low solubility or that are given a high dose enterally, do you expect dissolution or absorption to be the rate limiting step?

A

Dissolution controls the rate in these cases

30
Q

What are the advantages and disadvantages to oral administration of drugs?

A

Advantages:

  • Safe and Painless
  • Cheap
  • no need to sterilize

Disadvantages:

  • Slow onset usually > 1hr
  • Patient noncompliance
  • First pass metabolism - low bioavailability
31
Q

What two methods of GI administration allow for bypass of 1st pass metabolism?

A
  • Buccal

- Large Intestine

32
Q

Why are drugs absorbed so quickly by the buccal route of administration?
- what is the surface area and pH of the buccal route?

A

Thin Membranes
Good Blood Supply

pH = 7
Surface area = Small

33
Q

What areas of the GI tract have a large surface area?

- what is their pH?

A

Duodenum - pH = 5-6.5

Small Intestine - pH = 8

34
Q

How much time do drugs spend in:

  • Stomach
  • Duodenum
  • Small Intestine
A

Stomach - 30-40min
Duodenum - very short
Small intestine - Long ~3hr

35
Q

Why does increasing gastric emptying time typically increase drug absorption?
- how would you increase gastric emptying time?

A
  • Large surface area of the Small Intestine typically allows for better absorption so the quicker you get it out of the stomach and into the S.I. the better.
  • Gastric Emptying time can be increased by Taking drinking water with your pill
36
Q

Which would you expect to get absorbed better in the stomach: acidic or basic drug?

A

Acidic drugs because they will be neutral in the stomach and can more easily cross membranes

37
Q

What factors affect gastric emptying?

A

Volume of ingested material: Bulky Materials tend to empty more slowly than liquids

Type of Meal: Fatty Foods Decrease Gastric Emptying

Lying on the left side: Decreases Gastric Emptying (because pyloric sphincter is on the right)

Drugs: Anticholinergics, Narcotics, Analgesics reduce gastric emptying

38
Q

What are the advantages and disadvantages to administering a drug sublingually?

A

Advantages:

  • Avoid First Pass
  • Rapid absorption (good bs to the mouth)
  • Neutral pH in mouth means drug is stabile

Disadvantages:

  • Holding dose in the mouth is inconvenient
  • Useful when drug dosage is small
39
Q

Rectal Route advantages and disadvantages

A

Advantages:

  • Useful in Children
  • Unconscious/Vomitting Patients can take it
  • Not 1st pass

Disadvantages:

  • Absorption is erratic
  • People don’t like Sticking things up their ass
40
Q

There are lots of advantages and disadvantages to IV drug admin. What are some important ones?

A

Advantage

  • You can control how fast the drug gets in
  • high bioavailability

Disadvantage

  • Expensive because it must be sterile
  • you need trained personnel
41
Q

What are some advantages and disadvantages to Subcutaneous drug admin?

A

Adv.

  • no 1st pass
  • absorption can be varied with rapid aqueous solutions and slow delivery from insoluble preps.
  • Patient can give it themselves

Dis.

  • painful
  • local tissue damage
  • must be given in small volumes (2mL max)
42
Q

What are the advantages to IM admin?

A

Adv.

  • Avoid 1st pass
  • Rapid

Dis.

  • Trained personnel needed
  • Site of injection influences absorption
  • gender differences
  • Pain
  • Volume limited to (4-5 mL)
43
Q

Why would you give a drug intraarterially?

A

adv.
- Can be used to target specific organs

dis.
- Experts only can do this

44
Q

What is an intrathecal injection?

A
  • Injection into the subarchnoid space to rapidly transverse the BBB
45
Q

What are examples of some systemic and local drugs administered via inhalation?
*what to watch out for when giving these

A

Local - Bronchodilators
Systemic - General Anesthesia

  • Allergic Reactions can happen
46
Q

What chemical properties must a drug have that is given topically?

A

Must be lipid soluble

47
Q

What factors determine the Rate of Distribution of a drug?

A
  • Cardiac output and regional Blood Flow
  • Tissue Volume
  • Capillary Permeability
48
Q

What factors determine the Extent of Distribution for a drug?

A
  • Membrane Transport Abilities
  • Plasma Protein Binding
  • Intracellular Binding
49
Q

Where is total blood flow greatest in the body?
Which have the highest perfusion?
What is the consequence of this?

A
  • Brain
  • Kidneys
  • Liver
  • Muscle

Same for perfusion except muscle is not included and the Heart is

Consequence:
- These are the organs where you would expect drug concentration to rise the most rapidly

50
Q

Take a drug that is 30 kD in weight, how do you think it will be absorbed?

A

Most likely absorbed via Pinocytosis

51
Q

What two variations in capillary structure result in variation from normal Drug tissue permeability?

A
  1. Renal Capillaries have large fenestrations leading to more drugs going out of the capillary bed via Filtration
  2. Brain Capillaries have tight junctions creating the BBB
52
Q

How can plasma proteins affect the concentration of free drug in the blood?
- What plasma proteins are involved with what drugs generally?

A

Causes drugs to stay in the central blood compartment and limits distribution of free drug to its site of action

Albumin - soaks up acidic drugs
Globulins - soak up basic drugs

53
Q

What determines how much of a drug will be bound by a plasma protein?
- what does this entail?

A

AFFINITY of the Plasma Protein binding sites for the drug at low concentration

At high concentration the NUMBER of binding sites becomes the main variable

**Will show typical characteristics of binding kinetics, its a SATURABLE and NON-LINEAR process

54
Q

T or F: even slight changes in the percent of Drug bound to plasma protein can cause HUGE changes in the free drug concentration.

A

True, this is of greatest concern with drugs that have a narrow therapeutic window

55
Q

What is often the cause of Drugs accumulating in tissues?

- what are the kinetics of this process?

A

Active Transport into the tissue or Tight Binding to the Tissue

Kinetics = Reversible and Saturable

56
Q

What can be an advantage of ion trapping of a drug?

A

Bound ion Trapped Drugs are relatively inaccessible to systemic circulation and will be released at low levels over a long period of time to prolong the drugs effect

57
Q

What are some Common Reservoirs for Drugs?

- what drugs do they often trap?

A
  1. Stomach - Traps BASIC drugs due to ionization (ex. Codeine)
  2. Albumin - Limits the availability of free drug (Warfari 99% bound)
  3. Tissue - Liver Concentrates drugs like quinacrine
    - Thyroid concentrates Iodine
    - Bone - can accumulate Tetracycline, Divalent Chelating agents, and Heavy Metals
  4. Fat can accumulate lipid soluble compounds
58
Q

What is drug redistribution?

A
  • When the drug moves from the site of action to other tissues or to bound proteins
  • Direction of blood flow often affects this
59
Q

What are the 4 drug distibution patterns?

  • general types of drugs that lead to these patterns?
  • What pattern do most drugs adhere to?
A
  1. Drug remains largely in the vascular system
    - Plasma substitutes and Drugs Strongly bound to plasma Protein
  2. Uniform distribution through body water
    - Water soluble drugs (e.g. EtOH)
  3. Concentration into one or more tissues
    - Iodine in thyroid
    - Tetracycline in developing Teeth
  4. Non-uniform Distribution in the body MOST DRUGS
    - due combined effects of 1,2,3
60
Q

What is the Volume of Distribution and What is its formula?

A
  • Tells you what volume of H2O that drug is in
  • Tells you (generally) which compartment the drug is in

Vd = Drug administered / [Drug in Plasma]

61
Q

What are the volumes of distribution for:

  • Extracellular Fluid
  • Plasma
  • Intrerstitial Fluids
  • Intracellular Fluids
  • Total Body Water
A
  • Extracellular Fluid - 13-16 liters
  • Plasma - 4
  • Intrerstitial Fluids - 10-13
  • Intracellular Fluids - 25-28
  • Total Body Water - 40
62
Q

If a drug has a Vd of 8 what could you assume?

A

The drug is likely concentrated in the plasma or interstitial Fluid

63
Q

If a drug has a Vd of 35 what could you assume?

A

That it is uniformly distributed throughout the total body water

64
Q

If a drug has a Vd or 130 what could you assume?

A

The drug is concentrating in multiple tissues, really you would assume this with anything much greater than 40

65
Q

The effects of the body on the drug is what?

A

Pharmacokinectics

pharmacodynamics is what the body does to the drug

66
Q

Compare the Rate of Distribution to the Extent of Distribution based on the factors that they are dependent on.

A

Rate of Distribution:

  • Cardiac Output
  • Tissue Volume
  • Capillary Permeability

Extent of Distribution:

  • Membrane Transport Ability
  • Plasma Protein binding
  • Intracellular Binding

PHARMACOLOGY - Antiviral, Classic Chemo, ADME (18 decks)

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