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Primary FRCA > Pharmacology > Flashcards

Pharmacology Flashcards

1
Q

Isomerism

A

Structural - dynamic or static
Stereo - enantiomers or diastereoisomers

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2
Q

Chiral centre

A

Central atom bound to 4 dissimilar groups

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3
Q

Enantiomer

A

Stereoisomer with a single chiral centre, producing non-superimposable isomers

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4
Q

Tautomerism

A

Dynamic change between 2 different forms depending on environmental conditions, often pH

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5
Q

Optical isomerism

A

Ability to rotate polarised light in different directs

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6
Q

What is the time constant?

A

Time taken for plasma conc to fall to 0 if initial rate of elimination continued
Reciprocal of the rate constant 1/e
Always longer than half life (half life is shorter by a factor of 0.693)

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7
Q

Clearance

A

Volume of plasma cleared per unit time

Cl = Input/plasma conc

Cl = Ke x Vd (where Ke is elimination rate constant)

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8
Q

Loading dose - equation

A

Vd * desired concentration

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9
Q

Maintenance dose - equation

A

Steady state con x clearance

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10
Q

Zero Order Kinetics

A

Independent of the conc of reactants
Constant amount
Fixed amount cleared; half life decrease
No steady state reached - accumulation will occur e.g. ethanol

(may be due to maximal enzyme activity - some reactions will initially be first order then at saturation point become zero order e.g thiopentone)

Horizontal line on graph

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11
Q

First Order Kinetics

A

Dependent on conc of reactants.
Constant proportion
Half life and clearance are constant
Reaches steady state - doesn’t accumulate - propofol

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12
Q

Michaelis-Menten Equation

A

Predicts rate according to substrate concentration and specific enzyme characteristics

V= Vmax[substrate]/Km + [substrate]

Where Km = substrate conc at which velocity is half of max (equivalent to ED50)

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13
Q

Agonists

A

Demonstrate affinity and intrinsic activity;
full agonists = 1
partial agonists < 1

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14
Q

Antagonists

A

Demonstrate affinity but no intrinsic activity

Competitive antagonists:
-same site binding
-shift the dose response to the right, but can achieve the same Emax with increased dose

Non-competitive antagonists
-allosteric binding
-reduce the Emax, effect not overcome by ^^ dose

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15
Q

Mixed agonist/antagonists

A

Opioids - pentazocine, buprenorphine
Mirtazepine
Pindolol, xameterol

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16
Q

Volume of Distribution

A

Theoretical volume a drug would have to occupy to produce plasma conc.

Vd= dose/conc

Small non polar molecules distribute freely = large Vd 40L
Small polar molecules exit circulation to ECF = Vd ~ 14L
Large polar molecules trapped in circulation = small Vd 5l

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17
Q

When can Vd be larger than total body water?

A

This effect can be due to protein binding, plasma degradation, sequestration into other tissues e.g. propofol into adipose

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18
Q

Extraction ratio

A

The efficiency of an organ in eliminating a drug

If ER is high, then clearance depends only on blood flow.

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19
Q

Phase 1 Elimination Reactions

A

Makes a substance water soluble, unmasks function group

CYP450 reactions;
oxidation - barbs, benzos, paracetamol, omeprazole
reduction - prednisone to prednisolone
hydrolysis - mao > adrenaline, esterases > remifentanil, atracurium, alcohol dehydrogenase > ethanol to acetic acid

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20
Q

Phase 2 Elimination Reactions

A

Conjugation with a functional group

Glucuronidation - morphine activation, propofol inactiv
Acetylation - isoniazid, hydralazine
Sulphation - paracetamol
Methylation - catecholamines
Glutathione conjug - paracetamol

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21
Q

TCI Models

Marsh

A

Developed for plasma effect site

Requires lean body weight

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22
Q

TCI Models

Schnider

A

Requires ABW, age, height, gender
Smaller initial bolus so safer for old/frail/high ASA

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23
Q

Efficacy

A

Magnitude of receptor response

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24
Q

Affinity

A

Ability to bind to receptor
Reciprocal of the equilibrium dissociation constant

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25
Q

Potency

A

Conc (EC50) or dose (ED50) required to produce 50% max effect
LHS with increasing potency

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26
Q

Tolerance

A

Decrease in response following repeated administration
-pharmacodynamic: receptor subunit modification
-pharmacokinetic: CYP450 enzyme induction
-behavioural: learning to function

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27
Q

Tachyphylaxis

A

Hyperacute tolerance after only 1-2 doses

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28
Q

Adverse Drug Reactions

Type A

A

Augmented
85-90% of ADR
Related to pharmacological effects, dose related.
e.g. cough with ACEI

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29
Q

Adverse Drug Reactions

Type B

A

10-15% of ADRs
Unpredictable
e.g. MH, sux apnoea

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30
Q

Concentration effect

A

The phenomenon by which the speed of onset of inhalational anaesthetic agents is increased when they are administered with N2O

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31
Q

The Second Gas Effect

A

The phenomenon by which the rise in the alveolar partial pressure of nitrous oxide is disproportionately rapid when administered in high concentrations

N2O diffuses into blood faster than N2 diffuses out thereby shrinking the alveolar volume and concentrating the remaining gas

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32
Q

Volatiles

Lipid Solubility

A

Ability to cross the BBB and exert effect
Potency

High lipid solubility = high potency = low MAC = high OG coefficient

33
Q

Volatiles

Water Solubility

A

Ability to dissolve into the blood
Speed of onset

Low water solubility = slow speed of onset = low BG coefficient

34
Q

MAC

Definition

A

Minimum alveolar concentration of anaesthetic vapour @ equilibirum required to prevent movement to standard surgical stimulus in 50% of unpremedicated subjects at 1 atm

35
Q

MAC

Agents in ascending order

A

Halothane 0.75
Isoflurane 1.17
Enflurane 1.68
Sevo 2
Des 6.6
Xenon 71
N20 105

36
Q

Factors increasing MAC

A

Childhood

Hyperthermia/hyperthyroidism
Hypernatraemia

Catecholamines/sympathomimetics
Chronic opioids/ETOH
Acute Amphetamines

37
Q

Factors decreasing MAC

A

Neonates/old age
Pregnancy

Hypotension/hypothermia/hypothyroidism
Lithium

Alpha agonists/sedatives
Acute opioids/ETOH
Chronic amphetamines

38
Q

Critical temp = 36.5
Critical pressure = 72bar
Mol weight = 44
MAC = 105
BP = -88
SVP = 5200
BG = 0.47
OG = 1.4

A

Nitrous Oxide

Manufactured by heating ammonium nitrate to 250 C
Stored as a liquid in French blue, @ 5 bar
Filling ratio 0.75 (less in warmer climates)

39
Q

MW = 131
BP = -108
MAC = 71
BG = 0.14
OG = 1.9

A

Xenon

Odourless, inert gas produced by fractional distillation of air, expensive.

Variable increase in CBF; analgesic; no affect on contractility

40
Q

Halothane

A

Halogenated hydrocarbon containing bromine, chlorine and fluorine

41
Q

Henderson Hasselbach Equation

A

pH = pKa + log10 [HCO3-]/[H2CO3]

42
Q

Definition of pH

A

Negative log10 of H+ concentration - nmol.L

43
Q

Weak acids ionised above their pKa
Weak bases ionised below their pKa

A
44
Q

pKa

A

The pH at which 50% of the drug is ionised - exists in equal portions of ionised to unionised.

45
Q

Acidic Drugs

A

Aspirin

46
Q

Basic Drugs

A

Local anaesthetics
Morphine

47
Q

Drugs that cause uterine contraction

A

Syntocinon
Ergometrine
Prostaglandin F2 - carbaprost, haemabate

48
Q

Drugs that cause tocolysis

A

Salbutamol, terbutaline
Isoflurane/sevoflurane
Magnesium
Ritodrine
GTN

49
Q

Drugs that cross the placenta - lipid soluble, uncharged

A

Morphine
Warfarin
Lignocaine

50
Q

Drugs that prolong neuromuscular block

A

Antibiotics such as streptomycin, polymxyin and neomycin
Cocaine, procaine and lidocaine
Lithium due to its hypokalaemic effect
Verapmil and lidocaine by open channel block mechanism
Tricyclic antidepressants by closed channel block
Acidosis and hypercarbia
Hypothermia

51
Q

Tell me about Ketamine…

A

Phencyclidine derivative.
An acid (3.5-5.5) in solution, poor protein binding (12%), T1/2 of 3 hours.
S(+) enantiomer is 2-4x more potent and less psychoactive than the R(-).
Can be administered PO, IM, IV, PR, nasally as well as intrathecal/extradural.

Not a true IV induction agent as takes more than one arm-brain circulation.
Causes a state of dissociative anaesthesia.

Inc sympathetic outflow causes tachycardia and increased CO - good when sick but not in IHD.
Causes profound bronchodilator so useful adjunct for status asthmaticus.
Also used as infusion for refractory status epilepticus.

52
Q

What groups of drugs are associated with gynaecomastia?

A

Oestrogens or drugs with oestrogen like activity - digoxin!!
Drugs that enhance oestrogen synthesis
Drugs that inhibit testosterone synthesis or activity
Drugs that act by unknown mechanisms

53
Q

These drugs cause gynaecomastia by unknown mechanisms

A

Methyldopa
Busulfan
Amiodarone
TCAs
Diazepam
Omeprazole
Penicillamine
CCB
ACEI
Alcohol
Marijuana
Heroin

54
Q

Tell me about mannitol…

A

An osmotic diuretic filtered at the glomerulus but not reabsorbed, creating an osmotic gradient in the tubule, thus excreted with an osmotic equivalent of water.

Useful to force diuresis in drug overdose, cerebral oedema.

Also has oxygen free radical scavenging properties which may reduce the risk of reperfusion injury.

55
Q

Tell me about entonox…

A

Entonox is a 50:50 mix of oxygen and nitrous oxide.
Stored at 137bar in blue cylinders with blue and white quartered shoulders.

It has a pseudocritical temperature of -6 and can separate into its components below this.

It exhibits the Poynting effect - change in properties of a mixture not explained by the properties of the individuals.

56
Q

What is a prodrug?

A

A drug with no inherent activity that becomes converted to its active form when metabolised, e.g:

Enalapril - enalaprilat
Diamorphine - 6-monoacetlymorphine
Codeine - morphine
Parecoxib - valdecoxib

57
Q

What do these drugs have in common?

Cytotoxics
Thiazide diuretics
Furosemide
Ethambutol
Pyrazinamide
Sulphonamides
Salicylates

A

Cause hyperuricaemia

58
Q

What are the common side effects of loop diuretics?

A

High protein bound, secreted into tubular lumen by organic acid transporter
Inhibit the Na+/K+/2CL- co-transporter in the ascending LOH, increasing delivery of Na and H20 to the DCT.

Hypokalaemia
Hyponatraemia
Hypomagnesaemia
Metabolic alkalosis

59
Q

Long term effects of phenytoin…

A

Osteomalacia and osteoporosis
Hirsuitism
Gingivial hyperplasia
Ataxia

60
Q

Alpha half life in a two compartment model…

A

Initial distribution phase following drug administration, where drug equilibrates between the central and peripheral compartments

61
Q

Beta half life in a two compartment model…

A

The time required for the plasma drug concentration to decrease by half during elimination phase

Predominantly influenced by slower compartment

62
Q

Thiazide diuretics…

A

Inhibit transluminal NaCL transport in the early DCT
Inhibit NA reabsorption, stimulate excretion of Na, Cl and K - assoc with metabolic alkalosis
Reduce ECF - activates RAAS
Side effects:
Hypokalaemia, hypomagnesaemia, hypochloraemic alkalosis
Hypercalcaemia
Impaired glucose tolerance
Gout
Photosensitivity, rashes, postural hypotension, aplastic anaemia

63
Q

Drugs that reduce renal concentrating ability…

(cause diabetes insipidus)

A

Lithium
Gentamicin
Amphotericin B
Demeclocylcine

64
Q

CYP450 Inducers

A

Anticonvulsants - phenytoin, carbamazepine
Steroids
Antibiotics - rifampicin, griseofulvin
Nicotine, alcohol, St John’s Wort

65
Q

CYP450 Inhibitors

A

Azoles
Antibiotics - macrolides, sulfonamides, metro, cipro, chloramphenicol, isoniazid
Cimetidine
Omeprazole
Sodium valproate

66
Q

Metabolites of tramadol…

A

In humans the main metabolic pathways are N- and O-demethylation (phase I reactions) and conjugation of O-demethylated compounds (phase II reactions).

Eleven metabolites are known, five arising by phase I reactions (M1 to M5) and six by phase II reactions (glucuronides and sulfates of M1, M4 and M5).

The five phase I metabolites are

Mono-O-desmethyl-tramadol (M1)
Mono-N-desmethyl-tramadol (M2)
Di-N-desmethyl-tramadol (M3)
Tri-N,O-desmethyl-tramadol (M4) and
Di-N,O-desmethyl-tramadol (M5).
Eighty two per cent of tramadol is excreted unchanged.

67
Q

Weak acid pKa 11
Vd 4L/kg
>95% protein bound
Onset 60s
Duration 3-5mins
Clearance 25-50ml/kg/min
CSHT 20 mins (up to 8hr infusion)

A

Propofol
2,6 diisopropylphenol
Highly lipid soluble ilipd emulsion
Egg lecithin, soya bean protein - v low allergy risk in adults

Stimulates GABAa, inhibits NMDA, 5HT3 and D2

68
Q

Keto and enol forms depend on pH - tautomerism
Vd 2.5l/kg
pKa 7.6
65-80% protein bound
Onset 30s
Duration - rapid
Clearance 3ml/kg/min

A

Thiopentone
Barbiturate ring

Triexponential decline
Phenobarbitone - inactive metabolite
C/I in porphyria

CVS depressant, drops ICP, CBF, CMRO so good in TBI
Lowers IOP

69
Q

pKa 4.2 - prepared with propylene glycol
Vd 4.5l/kg
76% protein bound
Onset 10-60secs
Duration 6-10mins
Clearance 870-1700ml/min

85% renal excretion, 15% bile

A

Etomidate
Imidazole ring

Steroid suppression?
Resp relatively maintained - apnoea, TV down but RR up
CVS -stable, mild drop in MAP
CNS - vasoconstrictor

70
Q

pKa 7.5
Vd 3L/kg
Onset 30 secs
Clearance 18ml/kg/min
Racemic mixture - S more potent and less psychoactive

Na/Ca influx - K efflux

A

Ketamine
Phencyclidine derivative
Non-competitive NMDA antagonist
Dissociative anaesthesia - analgesia, amnesia, hypnosis and some LA action

Resp - bronchodilator, preserves reflexes
CVS - inc BP, HR, CO
CNS - inc ICP, emergence phenomena
GI - secretions ++
MSK - increased tone

71
Q

MW 200.1
BP 58.5
SVP 22.7
MAC 1.8
BG 0.7
OG 80

A

Sevoflurane (7 X F)
Polyfluorinated isopropyl methyl ether - no chiral centre
Stored with 300pm H2O to avoid Lewis acid reaction
Metabolised by CYP4502E1 - compound A ?toxic

Resp; pleasant odour and non-irritant, good for gas induction
CVS: lowers SVR, BP, coronary and cerebral vascular resistance
CNS: post op delirium in children

72
Q

MW 168
BP 23.5
SVP 89.2
MAC 6.6
BG 0.42
OG 29

A

Desflurane (6 X F)
Fluoroinated ethyl methyl ether
Tec 6 vaporiser at 39°C and 2 atm

0.02% metabolised, trifluoroacetic acid, low toxicity
Pungent smell
Low BG means fast onset/offset so good for prolonged surgery
Bad for the environment - highest global warming potential

73
Q

MW 184.5
BP 48.5
SVP 33.2
MAC 1.17
BG 1.4
OG 98

A

Isoflurane
Halogenated ethyl methyl ether - chiral centre at position 3

0.2% hepatic metabolism; renal tox is rare; trifluoroacetic acid

maintains CBF up to MAC 1
Coronary steal syndrome
Pungent/irritant but also bronchodilator

Produces CO when reacts with dry soda lime

74
Q

MW 184.5
BP 56.5
SVP 23.3
MAC 1.68
BG 1.8
OG 98

A

Enflurane
Halogenated ethyl methyl ether - chiral centre at end

Metabolised to organic and inorganic fluorides
Compound F

75
Q

MW 131
BP -108
SVP -
MAC 71
BG 0.14
OG 1.9

A

Xenon
Produced by fractional distillation of air = expensive

CVS: no effect on contractility
CNS: variable increase in CBF, analgesic

75
Q

MW 197
BP 50.2
SVP 32.3
MAC 0.75
BG 2.4
OG 224

A

Halothane
Halogenated hydrocarbon
Stored with 0.01% thymol to prevent liberation of bromine

CVS: myocardial depressant - inc vagal tone
CNS - most increase in CBF

Halothane hepatits? releases Br, Cl and F

76
Q
A
77
Q

MW 44
BP -88
SVP 5200
MAC 105
BG 0.47
OG 1.4

CT 36.5°C
CP 72bar

A

Nitrous Oxide
Manufactured by heating ammonium nitrate to 250°C
French blue cylinders at 51bar, filling ratio 0.75
Tare weight not gauge pressure
Diffusion hypoxia -
Oxidises cobalt in B12 - megaloblasts > agranulocytosis

78
Q
A

Primary FRCA (6 decks)

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