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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

25
What are the barriers to distribution?
Blood brain barrier - only lets lipid soluble drugs in Placental barrier - lipophilic again
26
What is metabolism performed by?
Enzymes
27
What is the primary site of drug metabolism?
Liver
28
What is metabolism?
Aim is to prepare drugs to excretion, though sometimes to convert into active state
29
What does metabolism do to lipid soluble drugs?
makes them more water soluble so they can be excreted by the kidneys
30
With enzymatic metabolism of drugs, what is phase 1 reactions?
- Catabolic reaction - Functionalisation Makes the drug have higher polarity thus more water soluble
31
With enzymatic metabolism of drugs, what is phase 2 reactions?
- Synthetic - Conjugation Drug combines with endogenous molecule - makes more water soluble
32
What is an isoenzyme
enzymes that catalyse the same reaction but have different: - amino acid sequences - kinetic parameters - substrate specificity - regulation
33
WHat are some variants of drug metabolisation?
- genetic factors - enzyme differences - Other drugs, good and drink - >competition - >induction
34
What is enzyme induction?
increase your ability to break down drug. Increase activity of metabolism enzymes increases rate of metabolism think alcohol
35
What is enzyme inhibition?
competition for the same metabolism enzyme decrease rate of metabolism
36
what are some routes of excretion?
- Biliary - renal - pulmonary - sweat - saliva - breast milk
37
What does clearance mean?
vol of plasma cleared of drug per unit of time
38
What are the major sites of drug clearance?
Kidneys | Liver
39
why is metabolism important for excretion?
If it isnt metabolised from lipophilic to hydrophilic state,, can easily be reabsorbed through tubules in kidney during excretion
40
What would happen with highly ionised molecules in the renal excretion?
gets trapped in tubules. Build up of drugs
41
what is ion trapping?
gets stuck in blood stream ca't get out in urine
42
What is first order kinetics
constant % of drug eliminated. Rate of elimination is relative to concentration of drug - has a half life
43
How many half lives are needed to get a drug below 10%
4
44
what are the benefits for intravenous infusion?
amount in = amount out can create a steady state of drug in the plasma
45
When do we start to reach plateau concentration with first order kinetics?
Approx 4-5 half lifes
46
What is zero order kinetics
rate of elimination is constant the rate of reaction is independent to concentration has no half life
47
What are some zero order kinetic drugs
warfarin heparin aspirin alcohol
48
What are some patient factors influencing metabolism and excretion?
Baby - organ function - fat distribution Elderly Illness Lifestyle
49
Should a child be treated as a small adult?
No
50
What are some factors of excretion and metabolism displayed by infants?
- drug metabolism less efficient | - renal function not fully developed
51
What are some metabolism factors displayed by children?
- over 2 can oxidise drugs more rapidly than adults | - conjugation r reactions develop more slowly
52
What are factors the elderly face when dealing with metabolism and excretion?
- decreased renal and hepatic capabilities - less enzymes - decreased in adipose tissue and muscle mass

PAR2031 - Pharmacology (13 decks)

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