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BRS YR2 > Principles of Pharmacology > Flashcards

Principles of Pharmacology Flashcards

1
Q

Pharmacology Definition

A

The study of drug action

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2
Q

Therapeutics Definition

A

Drug prescribing and the treatment of disease (more focused on the patient)

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3
Q

Pharmacodynamics

A

what the drug does to the body

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4
Q

Pharmacokinetics

A

what the body does to the drug

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5
Q

Main 3 questions for pharmacodynamics

A
  • Where is this effect produced?
  • What is the target for the drug?
  • What is the produced response after interaction with the target?
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6
Q

What are the 4 main drug targets?

A
  • Receptors
  • Enzymes
  • Ion channels
  • Transport proteins
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7
Q

Selectivity

A
  • lock and key model

- necessary for a drug to be an effective therapuetic agent

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8
Q

What is a factor that impacts dosage?

A

The selectivity of the drug, however it is difficult to accurately predict how much of a drug might bind to the desired target protein

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9
Q

What are the 4 ways drugs can interact with target receptors?

A
  • Electrostatic
  • Hydrophobic
  • Covalent
  • Stereospecific
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10
Q

What is an electrostatic interaction?

A

MOST COMMON

involves hydrogen bonds and Van der Waals forces

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11
Q

What is a hydrophobic interaction?

A

Involved with lipid-soluble drugs

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12
Q

What is a covalent interaction?

A

LEAST COMMON

tendency to be irreversible

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13
Q

What is a stereospecific interactions?

A

due to the presence of stereoisomers and interact stereospecifically with receptors.

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14
Q

Describe the relationship between drug+receptor and the drug-receptor complex

A

Proportional, at equilibrium

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15
Q

Agonists

A

drugs that bind and activate receptors

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16
Q

Antagonists

A

drugs that only bind tot he receptors

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17
Q

Affinity

A

determines the strength of the binding of the drug to the receptor, and therefore the drug-receptor complex

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18
Q

A high affinity leads to…

A

High receptor occupancy

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19
Q

Efficacy

A

the ability of an individual drug molecule to produce an effect once bound to a receptor

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20
Q

Difference between antagonists, partial agonists and full agonists

A

The size of the response caused by the binding of the drug molecule to the receptor

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21
Q

Potency

A

concentration or dose required to produce a defined effect.

22
Q

Measure of potency

A

the concentration/dose required to produce a 50% tissue response EC/D50
(half maximal effective concentration/dose)

23
Q

A highly potent drug…

A

produces a large response at relatively low concentrations

24
Q

A highly efficacious drug…

A

produces a maximal response, irrelevant of the drug concentration

25
Q

What are the 4 major pharmacokinetic factors?

A
  • Absorption
  • Distribution
  • Metabolism
  • Excretion
26
Q

Absorption

A

the passage of a drug from the site of administration into the plasma

27
Q

Bioavailability

A

the fraction of the initial dose that gains access to systematic circulation

28
Q

Difference between absorption and bioavailability

A

absorption is the process, whereas bioavailability is the outcome of the transfer

29
Q

What are the main forms of drug administration?

A 
- IV administration (100%)
Lower than 100%:
- Oral
- Inhalational
- Dermal (percutaneous)
- Intra-nasal
30
Q

What are the 2 main forms of drug transfer?

A
  • Bulk Flow transfer (bloodstream - 100%)
  • Diffusional transfer
    (molecule by molecule - <100%, lipid membrane)
31
Q

2 unlikely routes for diffusion

A
  • pinocytosis

- diffusion across aqueous route

32
Q

2 most likely routes for drug transport

A
  • diffusion across lipid membranes (only possible if lipid soluble)
  • carrier mediated transport (including a transmembrane protein)
33
Q

The solubility of most drugs is…

A

water soluble not lipid soluble

34
Q

What is the impact of ionisation on solubility?

A

The unionised form of the drug retains more lipid solubility, and therefore more likely to diffuse across lipid membranes.

35
Q

What does ionisation depend on?

A
  • The dissociation constant (pKa) of the drug

- The pH of the part of the body

36
Q

if the pKa (of the drug) and the pH (of the tissue) are equal…

A

The drug will be equally dissociated between the 2 forms

37
Q

What pKa do most weak acids have?

A

Between pKa 3-5

38
Q

For weak acids, as pH decreases…

A

The unionised form starts to dominate

39
Q

For weak acids, as the pH increases…

A

The ionised form starts to dominate

40
Q

Factors that effect tissue distribution

A
  • Regional blood flow
  • Plasma protein binding
  • Capillary permeability
  • Tissue localisation
41
Q

Regional blood flow by organs

A
  • Liver: 27%
  • Heart: 4%
  • Brain: 14%
  • Kidneys: 22%
  • Muscles: 20%
    changes depending on circumstance (exercise or food)
42
Q

Factors affecting plasma protein binding

A
  • the free drug concentration
  • the affinity for the protein binding sites
  • the plasma protein concentration
43
Q

What is the plasma concentration required for a clinical effect in the majority of drugs?

A

A maximum of 1.2mmol/l

the same as the binding capacity fo albumin alone

44
Q

Saturation and plasma protein binding

A

Plasma proteins are NEVER fully saturated

45
Q

What causes the difference in the extent of plasma protein binding?

A

Due to the particular affinity for the protein binding sites for that particular drug

46
Q

What nature of drugs bind better to plasma proteins?

A

Acidic drugs bind well to albumin.

47
Q

Why do drugs dissociate from plasma proteins?

A

Only free drug is able to diffuse out of blood and into tissues.

48
Q

What are the different types of capillary structure?

A
  • H2O filled gap junction, continuous
  • Tight junction (blood brain barrier)
  • Continuous, discontinuous and fenestrated
49
Q

Transport through continuous membranes.

A
  • Very lipid soluble: diffuse across endothelial cells

- Carrier proteins

50
Q

What are the benefits of the discontinuous capillaries in the liver?

A

Allows for drugs to easily diffuse out of the bloodstream and match the high metabolic demands of the liver

51
Q

The glomerulus of the kidney and fenestrated capillaries

A

Main function of the kidney is excretion

52
Q

What is the impact Tissue localisation on drug transport in the BBB?

A

Drugs move down the concentration gradient, the brain has a high concentration of lipids, the blood has a higher water content. Equilibrium means water soluble drugs are retains in the plasma and vice versa.

BRS YR2 (70 decks)

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