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Neuropharmacology > Lecture 1 > Flashcards

Lecture 1 Flashcards

1
Q

What is the clinical aim of a drug?

A

Achieved effective drug concentration at site of action long enough to produce a therapeutic effect

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2
Q

What is the therapeutic index?

A

Ratio of a drug’s toxic level to the level that provides therapeutic benefits

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3
Q

What is bioavailability?

A

Proportion of a dose that reaches systemic circulation

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4
Q

What does 100% bioavailability mean?

A

All of the unchanged drug has reached the site of action

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5
Q

Positives of intravenous injections

A
  • 100% bioavailability - rapid action
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6
Q

Negatives of intravenous injections

A
  • sterile equipment - trained personnel - expensive - potentially painful
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7
Q

Positives of Oral Administration

A
  • safest - most convenient - most cheap
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8
Q

Negatives of oral administration

A
  • always less than 100% bioavailability - destruction by enzymes, pH, bacteria - drugs can complex with food - absorption depends on rate of passage - irritation may cause vomiting - requires patient compliance
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9
Q

Factors affecting passive diffusion

A
  • size of drug molecule - ionisation of drug - lipid solubility
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10
Q

Which drug ionisation is better absorbed?

A

Unionised drugs

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11
Q

What is the main site of drug absorption?

A

small intestine

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12
Q

Why is the small intestine the main site of drug absorption?

A
  • large surface area - alkali pH - large blood flow from capillaries
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13
Q

What are the two other sites of drug absorption?

A

Stomach and colon

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14
Q

How does formulation affect GI absorption

A

Drug form affects likelihood of entering hepatic portal vein

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15
Q

Do tablets or fine particles better enter the hepatic portal vein

A

Fine particles

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16
Q

Two factors affecting rate of absorption

A
  • gut motility - splanchnic blood flow
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17
Q

Examples of orally administered drugs with potential problems

A
  • phenomethylpenicillin (pen V) - tetracyclines - aspirin (NSAIDS)
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18
Q

Phenomethylpenicillin (pen v) issue

A
  • absorbed by food - reduced bioavailability when this happens
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19
Q

Tetracyclines issue

A

Chelate metals so absorption reduced by milk, antacids, and iron preparations

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20
Q

Aspirin (NSAIDS) issue

A
  • irritate the stomach= dyspepsia, nausea, vomiting and diarrhoea - gastric damage
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21
Q

Issues of taking antibiotics and oral contraceptives

A
  • drug interactions - oral contraceptives undergo enterohepatic cycling
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22
Q

first pass metabolism

A

Degradation of an orally administered drug caused by enzyme metabolism in the liver and gut lumen before the drug reaches the systemic circulation

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23
Q

Why is a high first pass metabolism bad

A
  • orally ineffective - a drug will be broken down before it reaches system circulation
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24
Q

Different routes of administration

A
  • inhalation - transdermal - buccal and sublingual - intranasal - rectal - subcutaneous - intramuscular
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25
Q

Inhalation mechanisms

A
  • absorption depends on particle size - lipid soluble anaesthetics
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26
Q

Transdermal mechanisms

A
  • stratum corneum acts as a rate limiting step - lipophilic - low input rates (slow absorption)
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27
Q

Examples of transdermal drugs

A
  • nicotine patches - HRT (oestrogen/progesterone) - fentanyl patches - ibuprofen gels
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28
Q

Buccal and sublingual mechanisms

A

Passive absorption, washed away by saliva

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29
Q

Examples of buccal and sublingual drugs

A
  • GTN (angina) - temgesic (buprenorphine)
30
Q

Intranasal mechanisms

A
  • epithelial metabolism - passive diffusion
31
Q

Examples of intranasal drugs

A
  • GTN (angina) - desmopressin (diabetes insipidus, nocturnal enuresis)
32
Q

Rectal mechanisms

A
  • avoids first pass metabolism in the middle/lower rectum - erratic passive diffusion
33
Q

Examples of rectal drugs

A
  • diazepam rectal tubes (status epilepticus) - diclofenac suppositories (pain and inflammation)
34
Q

Subcutaneous mechanisms

A
  • passive diffusion to primary absorption capillary wall - lipophilic, water soluble - dependent on blood flow/release from dosage form - slow absorption rate
35
Q

Examples of subcutaneous drugs

A
  • insulin - heparin - growth hormone
36
Q

Intramuscular mechanisms

A
  • reliable route - quick uptake into body - good for depot preparations (long lasting) - absorption is perfusion limited- exercise
37
Q

Examples of intramuscular drugs

A
  • vaccines - antipsychotics - contraceptives
38
Q

Which route of administration has the shortest duration

39
Q

Which route of administration has the longest duration?

A

Intravenous

40
Q

What type of proteins do drugs bind to?

A

Plasma proteins

41
Q

What are the three plasma proteins that drugs bind to?

A
  • plasma albumin - beta globulin - acid glycoprotein
42
Q

Which protein binds to weak acids?

43
Q

Which proteins bind to weak bases?

A

Acid glycoprotein

44
Q

What is the relationship between dose and free (active) concentration?

A

Non-linear

45
Q

How does a small increase in drug concentration create a large increase in free drug concentration?

A
  • majority of the drug has already been bound - increases in concentration= more free drug in the plasma - few proteins to bind to
46
Q

What is a concern of taking drugs like aspirin/sulphonylureas?

A

Drug interactions

47
Q

How do drug interactions increase the likelihood of overdose?

A
  • two drugs can be bound to plasma proteins - binding of one drug can prevent the binding of the other - large concentration of free drug=overdose
48
Q

What factors affect tissue distribution?

A
  • lipid solubility - plasma protein binding - molecular weight ETC
49
Q

Which drug will end up leaving the plasma- heparin or ethanol?

50
Q

Which drug will end up diffusing from the extracellular space into the total body water- theophylline or paracetamol

A

Paracetamol

51
Q

How do lipid soluble drugs pass the blood brain barrier?

A

Passive diffusion

52
Q

How do water soluble drugs pass pass the blood brain barrier?

A

Carrier mechanisms

53
Q

Which cells in the liver metabolise drugs?

A

Hepatocytes

54
Q

What happens to drugs after metabolism?

A
  • converted to inactive metabolites - converted to active metabolites e.g. benzodiazepines - excreted unchanged
55
Q

Where does drug metabolism occur?

56
Q

Which enzyme carries out phase 1 metabolism?

A

Cytochrome P450 enzymes

57
Q

Describe phase 1 of drug metabolism

A
  • transforms molecular structure of the drug e.g. oxidation, hydrolysis, reduction - introduce a polar group and increase water solubility - abolishes activity - produces toxic or non-toxic metabolites
58
Q

Which enzyme carries out phase 2 metabolism?

A

Transferases

59
Q

Describe phase 2 (conjugation) metabolism

A
  • attaches endogenous substance (e.g. sulphate) to parent drug/phase 1 metabolite - increases polarity/water solubility so can be exerted in urine or bile
60
Q

What type of metabolites does phase 1 metabolism produce?

61
Q

What type of metabolites does phase 2 metabolism produce?

62
Q

Why is there a concern of a drug interaction from parent drug/metabolites?

A

Parent drug/metabolites can inhibit/induce metabolism of other drugs

63
Q

What is the major route of excretion?

64
Q

Is the bound or unbound drug excreted?

65
Q

What is the consequence of lipid soluble drugs being reabsorbed in renal tubules?

A

Action is prolonged

66
Q

How does changing urinary pH aid excretion?

A

Polarises and ionises the drug which aids excretion e.g. bicarbonate and aspirin

67
Q

Consequence of kidney damage for excretion

A

Drug accumulation

68
Q

Which form of drug is the most dangerous when kidney damage occurs- changed or unchanged drugs

A

Unchanged e.g. lithium, penicillins, atenolol

69
Q

Possible consequences of biliary excretion into intestine

A
  • conjugation - reabsorption from bile (enterohepatic circulation) back into the bloodstream e.g. imipramine, morphine
70
Q

Alternative routes of excretion

A
  • saliva - sweat - tears - expired air - breast milk

Neuropharmacology (15 decks)

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