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EDAIC PART II > Pharmacology > Flashcards

Pharmacology Flashcards

1
Q

How do drugs work? Targets from drug mechanism?

A
  1. Receptors
  2. Carriers
  3. Channels
  4. Enzymes
  5. Neutralisation (Physiochemical)
  6. Chelation (Physiochemical)
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2
Q

Example of drug mechanism of action?

A
  1. Acetylcholinesterase inhibitor (Neostigmine)
  2. Pyridostigmine - Myasthenia gravis
  3. Voltage gated sodium channels - LA
  4. Na/K-ATPase - Digoxin inhibition - Myocardial Stabilization
  5. Chelation - Roc + Sugammadex
  6. Neutralization - Citrate / activated charcoal
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3
Q

Properties of agonists?

A
  1. Increasing the dose increaes the effect
  2. They produce maximal effect
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4
Q

Properties of partial agonists?

A
  1. Produce submaximal effect
  2. Low efficacy
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5
Q

Properties of antagonists?

A
  1. Bind to receptor with no intrinsic activity
  2. May displace agonists from receptors
  3. No efficacy
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6
Q

What is drug efficacy?

A
  1. Ability to produce maximal effect
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7
Q

What is potency?

A
  1. Dose required to generate effect
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8
Q

What is the semilogarithmic plot?

A
  1. Used to assess efficacy and potency
  2. Assesses concentration and receptor response
  3. Negative log of conc of drug at which half-maximal response occurs is used to compare drug potency.
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9
Q

What is oral bioavailability?

A

This is the fraction of drug reaching the systemic circulation unchanged after oral administration.

It is the ratio of the area under the plasma concentration-time curve for oral and IV doses

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10
Q

Factors affecting bioavailability?

A
  1. Impaired GIT motility or rapid transit
  2. Neutralisation - Activated charcoal
  3. Mucosal surface area
  4. Blood flow
  5. Hepatic function & 1st pass metabolism
  6. Drug - SR preparations
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11
Q

Patient factors influencing drug effects? in relation to Absorption, distribution, metabolism and elimination.

A
  1. Acquired or inherited
  2. Physiological
  3. Pathological
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12
Q

Physiological changes affecting drug effetcs? Especially volume of distribution?

A
  1. TBW
  2. Fat
  3. Compartment size
  4. Protein binding
  5. Age-related decline in organ function
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13
Q

Patholgical changes aftecting drug action?

A
  1. Renal impairment
  2. Hepatic impairment
  3. Pyrexia & acidosis
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14
Q

Examples of drugs affected by pathological conditions?

A
  1. Atracurium rapid breakdown with pyrexia & acidosis (Short duration of action)
  2. Intropes and vasopressors - Acidosis
  3. Codeine - CYP2D6 mutation
  4. Sux apnoea- Defective plasma cholinesterase
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15
Q

How is codeine converted?

A

Converted to Morphine by O-demethylation by CYP2D6

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16
Q

What is the structure of GABAa receptor?

A
  1. It is a pentameric structure
  2. Its a ligand-gated ion channel
  3. It contains 5 protein subunits - 2A/2B/1G
  4. Inward conductance of chloride ions
  5. Hyperpolarisation + Inhibition of synaptic transmission
  6. Propofol, Etomidate, Thiopental and Benzo
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17
Q

What are the determinants of the speed of onset of IV induction agents?

A
  1. Speed of injection
  2. CBF
  3. Protein binding, pH & pKa
  4. Lipid solubility
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18
Q

Termintion of action of IV hypnotics?

A
  1. Diffusion out of the brain
  2. Diffusion into the tissue
  3. Slow release back into plasma
  4. Transfer to the liver for metabolism
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19
Q

After terminatio of infusion, what influences the CSHT? - Prolongs the effect

A
  1. Fatty tissue - Slow blood flow
  2. Hepatic metabolism
  3. A reverse gradient is produced
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20
Q

Action of propofol?

A
  1. Direct vasodilatory effect
  2. Loss of sympathetic tone
  3. Decreased venous return, RV filling & CO
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21
Q

What patients are suscptible to the hypotensive response seen with propofol?

A
  1. Cardiomyopathy
  2. Stenotic valvular lesions
  3. Constrictive pericardial disease
  4. Right - Left intracardiac shunts
  5. Antihypertensive medications
22
Q

What is an enzyme?

A

This is a biological catalyst which increases the speed of chemical reaction without being consumed in the reaction itself.

23
Q

List drugs which induce hepatic cytochrome P450 enzyme system?

A
  • Barbiturates
  • Phenytoin
  • Carbamazepine
24
Q

List drugs which inhibit hepatic cytochrome P450 enzyme system?

A
  • Amiodarone
  • Oral hypoglycaemics
  • Antibiotics
25
Q

What is a first order reaction?

A

The reaction is dependent on the concentration of the components of the reaction. This is an exponential process.

26
Q

What is a zero order reaction ?

A

The rate of reaction is independent of concentration, hence it is constant

27
Q

What happens when an enzyme system is saturated ?

A

A first order reaction may become a zero order reaction once enzyme system is saturated

28
Q

what is the Meyer-Overton hypothesis ?

A

The potency of an anaesthetic agent is related to its lipid solubility

29
Q

List common anaesthetic agents in order of increasing potency ?

A
  • Nitrous
  • Xenon
  • Desflurane
  • Sevoflurane
  • Enflurane
  • Isoflurane
  • Halothane
30
Q

What is a summative reaction?

A

The action of both drugs are additive but have actions of their own. Example: Midazolam & Propofol

31
Q

What is potentiation?

A

The action of one drug is amplified by another which has no independent action of its own . Example: Penicillin & Heparin

32
Q

what is synergism?

A

The combined action of two drugs is greater than one alone - Propofol & Remifentanil

33
Q

What is a Ligand?

A

This is a chemical messenger that is able to bind to a receptor. May be endogenous or exogenous

34
Q

What is a receptor?

A

This is the component of a cell which is able to interact with a compound selectively to initiate a biochemical change

35
Q

What is the law of mass action?

A

The rate of a reaction is proportional to the concentration of the reacting compounds

36
Q

What is affinity?

A

A measure of how avidly a drug binds to a receptor

37
Q

How can affinity be measured?

A

This can be measured as concentration of a drug that occupies 50% of the available receptor

38
Q

What is efficacy?

A
  • Intrinsic activity
  • Measure of magnitude of effect
39
Q

What is potency ?

A

This is the measure of the quantity of drug needed to produce maximal effect.

40
Q

How is potency measured?

A

It is measured using the median effective dose (ED50)

41
Q

What is the median effective concentration?

A

The concentration of a drug that induces effect halfway between baseline and maximal effect

42
Q

What is the median effective dose?

A

The dose of a drug that induces effect in 50% of the population (ED 50)

43
Q

Describe EC50 & ED50 in relation to potency?

A

A drug with a low EC50 or ED50 will have a higher potency

44
Q

Draw the log-dose response curve?

A

The attached image can be used to define drug interaction

45
Q

What is the median lethal dose?

A

This is the dose of drug that is lethal in 50% of the population (LD50)

46
Q

What is the therapeutic index?

A

This is the balance between beneficial and toxic effect. It is LD50/ED50

47
Q

What is an agonist?

A
  • It has affinity
  • It has intrinsic activity
  • Induces a response
48
Q

What is an antagonist?

A
  • Affinity
  • No intrinsic activity
49
Q

What is a full agonist ?

A

This is a drug which produces maximal response once bound to receptor.

50
Q

What is a partial agonist?

A

This is a drug with significant affinity but submaximal intrinsic activity. They lack efficacy

51
Q

Agonist curves, please see attached diagrams..

A

Review the potency of the different drugs in the curve

52
Q

Describe an alternative partial agonist?

A

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EDAIC PART II (15 decks)

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