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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
Potency
Conc (EC50) or dose (ED50) required to produce 50% max effect LHS with increasing potency
26
Tolerance
Decrease in response following repeated administration -pharmacodynamic: receptor subunit modification -pharmacokinetic: CYP450 enzyme induction -behavioural: learning to function
27
Tachyphylaxis
Hyperacute tolerance after only 1-2 doses
28
Adverse Drug Reactions Type A
Augmented 85-90% of ADR Related to pharmacological effects, dose related. e.g. cough with ACEI
29
Adverse Drug Reactions Type B
10-15% of ADRs Unpredictable e.g. MH, sux apnoea
30
Concentration effect
The phenomenon by which the speed of onset of inhalational anaesthetic agents is increased when they are administered with N2O
31
The Second Gas Effect
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
32
Volatiles Lipid Solubility
Ability to cross the BBB and exert effect Potency High lipid solubility = high potency = low MAC = high OG coefficient
33
Volatiles Water Solubility
Ability to dissolve into the blood Speed of onset Low water solubility = slow speed of onset = low BG coefficient
34
MAC Definition
Minimum alveolar concentration of anaesthetic vapour @ equilibirum required to prevent movement to standard surgical stimulus in 50% of unpremedicated subjects at 1 atm
35
MAC Agents in ascending order
Halothane 0.75 Isoflurane 1.17 Enflurane 1.68 Sevo 2 Des 6.6 Xenon 71 N20 105
36
Factors increasing MAC
Childhood Hyperthermia/hyperthyroidism Hypernatraemia Catecholamines/sympathomimetics Chronic opioids/ETOH Acute Amphetamines
37
Factors decreasing MAC
Neonates/old age Pregnancy Hypotension/hypothermia/hypothyroidism Lithium Alpha agonists/sedatives Acute opioids/ETOH Chronic amphetamines
38
Critical temp = 36.5 Critical pressure = 72bar Mol weight = 44 MAC = 105 BP = -88 SVP = 5200 BG = 0.47 OG = 1.4
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
MW = 131 BP = -108 MAC = 71 BG = 0.14 OG = 1.9
Xenon Odourless, inert gas produced by fractional distillation of air, expensive. Variable increase in CBF; analgesic; no affect on contractility
40
Halothane
Halogenated hydrocarbon containing bromine, chlorine and fluorine
41
Henderson Hasselbach Equation
pH = pKa + log10 [HCO3-]/[H2CO3]
42
Definition of pH
Negative log10 of H+ concentration - nmol.L
43
Weak acids ionised above their pKa Weak bases ionised below their pKa
44
pKa
The pH at which 50% of the drug is ionised - exists in equal portions of ionised to unionised.
45
Acidic Drugs
Aspirin
46
Basic Drugs
Local anaesthetics Morphine
47
Drugs that cause uterine contraction
Syntocinon Ergometrine Prostaglandin F2 - carbaprost, haemabate
48
Drugs that cause tocolysis
Salbutamol, terbutaline Isoflurane/sevoflurane Magnesium Ritodrine GTN
49
Drugs that cross the placenta - lipid soluble, uncharged
Morphine Warfarin Lignocaine
50
Drugs that prolong neuromuscular block
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
Tell me about Ketamine...
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
What groups of drugs are associated with gynaecomastia?
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
These drugs cause gynaecomastia by unknown mechanisms
Methyldopa Busulfan Amiodarone TCAs Diazepam Omeprazole Penicillamine CCB ACEI Alcohol Marijuana Heroin
54
Tell me about mannitol...
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
Tell me about entonox...
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
What is a prodrug?
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
What do these drugs have in common? Cytotoxics Thiazide diuretics Furosemide Ethambutol Pyrazinamide Sulphonamides Salicylates
Cause hyperuricaemia
58
What are the common side effects of loop diuretics?
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
Long term effects of phenytoin...
Osteomalacia and osteoporosis Hirsuitism Gingivial hyperplasia Ataxia
60
Alpha half life in a two compartment model...
Initial distribution phase following drug administration, where drug equilibrates between the central and peripheral compartments
61
Beta half life in a two compartment model...
The time required for the plasma drug concentration to decrease by half during elimination phase Predominantly influenced by slower compartment
62
Thiazide diuretics...
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
Drugs that reduce renal concentrating ability... (cause diabetes insipidus)
Lithium Gentamicin Amphotericin B Demeclocylcine
64
CYP450 Inducers
Anticonvulsants - phenytoin, carbamazepine Steroids Antibiotics - rifampicin, griseofulvin Nicotine, alcohol, St John's Wort
65
CYP450 Inhibitors
Azoles Antibiotics - macrolides, sulfonamides, metro, cipro, chloramphenicol, isoniazid Cimetidine Omeprazole Sodium valproate
66
Metabolites of tramadol...
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
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)
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
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
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
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
Etomidate Imidazole ring Steroid suppression? Resp relatively maintained - apnoea, TV down but RR up CVS -stable, mild drop in MAP CNS - vasoconstrictor
70
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
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
MW 200.1 BP 58.5 SVP 22.7 MAC 1.8 BG 0.7 OG 80
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
MW 168 BP 23.5 SVP 89.2 MAC 6.6 BG 0.42 OG 29
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
MW 184.5 BP 48.5 SVP 33.2 MAC 1.17 BG 1.4 OG 98
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
MW 184.5 BP 56.5 SVP 23.3 MAC 1.68 BG 1.8 OG 98
Enflurane Halogenated ethyl methyl ether - chiral centre at end Metabolised to organic and inorganic fluorides Compound F
75
MW 131 BP -108 SVP - MAC 71 BG 0.14 OG 1.9
Xenon Produced by fractional distillation of air = expensive CVS: no effect on contractility CNS: variable increase in CBF, analgesic
75
MW 197 BP 50.2 SVP 32.3 MAC 0.75 BG 2.4 OG 224
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
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77
MW 44 BP -88 SVP 5200 MAC 105 BG 0.47 OG 1.4 CT 36.5°C CP 72bar
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

Primary FRCA (6 decks)

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