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PAR2031 - Pharmacology > Week 3 > Flashcards

Week 3 Flashcards

1
Q

What is needed for a drug to be effective?

A
  • drug dose
  • PK plasma
  • Transport
  • PK Biophase
  • binding
  • Signal transduction
  • target activation
  • effect
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2
Q

What is PK plasma?

A

The drug getting into the blood stream?

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3
Q

What is PK Biophase?

A

What the body does with the drug

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4
Q

What is pharmacokinetics?

A

The study of the movement of drugs into, within, and out of the body and the factors effecting this…..

what the body does to the drug

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5
Q

what are the 4 key components of pharmacokinetics?

A
  • absorption
  • Distribution
  • Metabolism
  • Excretion
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6
Q

what is the goal of drug therapy?

A

achieving efficacy without toxicity

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7
Q

What factors affect drug absorption?

A
  • Nature of cell membrane
  • Blood flow
  • Solubility
  • Ionisation
  • Formulation
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8
Q

How does ionisation affect drug movement through membranes?

A

slightly ionised - move through well

high ionisation - hard to move through

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9
Q

What is the pH of most drugs?

A

Weak acids

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10
Q

What are the 3 transports through cellular membrane?

A
  • diffusion through lipid
  • diffusion through aqueous channels
  • Carriers
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11
Q

What affects the passive diffusion of drugs?

A
  • Size (<500)
  • Lipid solubility
  • pKa/ionisation
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12
Q

What does pKa mean?

A

relates to ionisation of drugs and ph environments and how they interact

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13
Q

describe ionised

A
  • charged

- low lipid solubility

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14
Q

describe unionised

A
  • uncharged

good lipid solubility

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15
Q

How to weak and strong acids move across membranes?

A

Weak acids move well

strong acids don’t

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16
Q

What is bioavailability?

A

Proportion of drug that reaches the systemic circulation as intact drug

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17
Q

What are factors the influence oral bioavailability?

A

DRUG FACTORS

  • pH
  • size
  • susceptibility to breakdown/ digestion in gut
  • susceptibility to breakdown liver enzymes

PATIENT FACTORS

  • presence of food
  • gastric motility
  • blood flow
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18
Q

What are the factors that affect drug distribution?

A

HO EASILY IT MOVES OUT OF THE VASCULATURE

  • Size
  • lipophilic tendency of the drug
  • degree of ionisation
  • binding to the plasma proteins

HOW WELL IT”S DELIVERED TO THE TISSUES
- blood flow to a particular region

WHETHER ITS HELD IN TISSUE
- binding to extravascular sites including tissues

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19
Q

What happens when drugs bind to plasma?

A

Drugs bind to plasma are confined to the vascular compartments and cannot interact with target, enter cells etc.

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20
Q

Why causes drugs to bind in plasma?

A

the drug binds to proteins and become too large to move through membrane

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21
Q

what does volume of distribution mean?

A

the amount of drug that has left the plasma/appears to be distributed

22
Q

What can lead to a larger volume of distribution?

A

drug distributed to more compartments

23
Q

What are the implications of a higher volume of distribution?

A

Higher VD -> less in plasma -> decreased elimination

24
Q

What is the half life of a drug with High VD

A

Longer

25
Q

What are the barriers to distribution?

A

Blood brain barrier - only lets lipid soluble drugs in

Placental barrier - lipophilic again

26
Q

What is metabolism performed by?

A

Enzymes

27
Q

What is the primary site of drug metabolism?

A

Liver

28
Q

What is metabolism?

A

Aim is to prepare drugs to excretion, though sometimes to convert into active state

29
Q

What does metabolism do to lipid soluble drugs?

A

makes them more water soluble so they can be excreted by the kidneys

30
Q

With enzymatic metabolism of drugs, what is phase 1 reactions?

A
  • Catabolic reaction
  • Functionalisation

Makes the drug have higher polarity thus more water soluble

31
Q

With enzymatic metabolism of drugs, what is phase 2 reactions?

A
  • Synthetic
  • Conjugation

Drug combines with endogenous molecule

  • makes more water soluble
32
Q

What is an isoenzyme

A

enzymes that catalyse the same reaction but have different:

  • amino acid sequences
  • kinetic parameters
  • substrate specificity
  • regulation
33
Q

WHat are some variants of drug metabolisation?

A
  • genetic factors
  • enzyme differences
  • Other drugs, good and drink
  • > competition
  • > induction
34
Q

What is enzyme induction?

A

increase your ability to break down drug.

Increase activity of metabolism enzymes
increases rate of metabolism

think alcohol

35
Q

What is enzyme inhibition?

A

competition for the same metabolism enzyme

decrease rate of metabolism

36
Q

what are some routes of excretion?

A
  • Biliary
  • renal
  • pulmonary
  • sweat
  • saliva
  • breast milk
37
Q

What does clearance mean?

A

vol of plasma cleared of drug per unit of time

38
Q

What are the major sites of drug clearance?

A

Kidneys

Liver

39
Q

why is metabolism important for excretion?

A

If it isnt metabolised from lipophilic to hydrophilic state,, can easily be reabsorbed through tubules in kidney during excretion

40
Q

What would happen with highly ionised molecules in the renal excretion?

A

gets trapped in tubules. Build up of drugs

41
Q

what is ion trapping?

A

gets stuck in blood stream ca’t get out in urine

42
Q

What is first order kinetics

A

constant % of drug eliminated. Rate of elimination is relative to concentration of drug

  • has a half life
43
Q

How many half lives are needed to get a drug below 10%

A

4

44
Q

what are the benefits for intravenous infusion?

A

amount in = amount out

can create a steady state of drug in the plasma

45
Q

When do we start to reach plateau concentration with first order kinetics?

A

Approx 4-5 half lifes

46
Q

What is zero order kinetics

A

rate of elimination is constant

the rate of reaction is independent to concentration

has no half life

47
Q

What are some zero order kinetic drugs

A

warfarin
heparin
aspirin
alcohol

48
Q

What are some patient factors influencing metabolism and excretion?

A

Baby

  • organ function
  • fat distribution

Elderly

Illness

Lifestyle

49
Q

Should a child be treated as a small adult?

A

No

50
Q

What are some factors of excretion and metabolism displayed by infants?

A
  • drug metabolism less efficient

- renal function not fully developed

51
Q

What are some metabolism factors displayed by children?

A
  • over 2 can oxidise drugs more rapidly than adults

- conjugation r reactions develop more slowly

52
Q

What are factors the elderly face when dealing with metabolism and excretion?

A
  • decreased renal and hepatic capabilities
  • less enzymes
  • decreased in adipose tissue and muscle mass

PAR2031 - Pharmacology (13 decks)

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