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Pharmacology Flashcards

1
Q

Levidopa/Carbidopa

A

Used in Parkison’s.
Levodopa = metabolic precursor of dopamine.
Carbidopa = peripheral decarboxylase inhibitor, which prevents peripheral breakdown to increase CNS levels.

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2
Q

Selegline

A

MAO-B inhibitor
Used in early Parkinson’s as breaks down dopamine selectively.
Caution with SSRIs.

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3
Q

Entacapone

A

Used in Parkinson’s to increase the half-life of L-dopa so there are less motor fluctuations and dyskinesia.

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4
Q

Donepezil

A

Selective reversible AChE inhibitor.
Binds at peripheral site.
Given once daily.
Dose 5-10mg.
ADRs: N+V, insomnia, diarrhoea, bradycardia.

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5
Q

Rivastigmine

A

Reversible AChE inhibitor. Also acts on butylcholinesterase.
Given BD.
Dose 1.5-6mg BD.
Also available as transdermal patch.

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6
Q

Galantamine

A

Selective competitive AChE inhibitor. Also acts as antagonist at nicotinic receptors.
Given BD.
Dose 12mg BD.
ADRs: N+V.
Not subsidised in NZ.

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7
Q

Memantine

A

NMDA-receptor antagonist.
Blocks excitotoxic glutamate activity.
Indicated in moderate/severe dementia.

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8
Q

Acetylcholinesterase inhibitors

A

Indications: Alzheimer’s, Lewy body, Parkinson’s, vascular dementia.
Better evidence in mild/mod than severe.
Contraindications: FTD, pure alcoholic dementia, large strokes, MCI.
Stabilise symptoms for 6-12 months, with subtle improvement in 50% (sx improved include apathy, spontaneity, delusions/hallucinations).

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9
Q

Bupropion

A

Dopamine + NA reuptake inhibitor.
Indicated in smoking cessation (reduces withdrawals, post-cessation weight gain) and depression.
ADRs: psychiatric sx, seizures

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10
Q

Varenicline

A

Nicotine α4β2 partial receptor agonist
Indicated in smoking cessation
ADRs: nausea, dry mouth, depression/SI

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11
Q

Disulfiram

A

Prevents ETOH breakdown by aldehyde dehydrogenase.
Indicated in alcohol abuse as negative reinforcement.
ADRs: can affect liver and thyroid

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12
Q

Naltrexone

A

Opiate receptor antagonist
Used in alcohol dependence as reduces pleasure, no withdrawal, no negative effects, minimal ADRs/interactions
But high relapse rate, withdrawal sx if using opiates

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13
Q

Acamprosate

A

GABA analogue, acts on GABA and glutamate systems, allosteric modulator of GABA-A
Used in alcohol dependence
Dose: <60kg = 333mg TDS, >60kg = 666mg TDS

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14
Q

Lofexidine

A

α2A adrenergic receptor agonist
Can be used in opiate withdrawal to reduce sx

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15
Q

Methadone

A

Full opioid agonist
Start low and give incremental doses as per withdrawal scale
Usual dose 60-120mg, can take 6 weeks to stabilise
Need to monitor LFTs and QTc
Advantages: well absorbed, long half-life (OD dosing, in urine for 3 days), used in pregnancy

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16
Q

Suboxone

A

Buprenorphine (long acting partial mu agonist, weak kappa agonist, delta agonist) + naloxone (opioid antagonist).
Diminishes cravings and helps with withdrawal.
Safe in overdose due to ceiling effect. Blocks other opioid agonists in dose-dependent fashion. Can precipitate withdrawal so first dose given when already in withdrawal.
Usual dose 2-8mg. Half-life 24-37 hours.
Advantages: milder withdrawal, alleviates cravings, long-acting, greater blockade effect
Caution with CYP3A4 inhibitors (inducer).

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17
Q

First generation antipsychotics

A

Predominantly dopamine blockers in mesolimbic pathway (to reduce psychotic sx), but not selective, so also act on mesocortical (secondary negative sx, depression, cognitive dysfunction), nigrostriatal (EPSE) and tuberoinfundibular (raised PL) pathways.

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18
Q

Second generation antipsychotics

A

Combination of D2 blockade plus 5HT-2 blockade, which causes reciprocal increase in dopamine, so effects more specific to mesolimbic pathway, with reduced side effects.
Variable in how tightly they bind D2 and how quickly they dissociate.
If used in high doses, dopamine blockade exceeds 60-80%, and they start to act as typical antipsychotics.

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19
Q

Benztropine

A

Anticholinergic and antihistamine
Used in movement disorders, such as parkinsonism and dystonia, and EPSE, such as akathisia.
Not useful in tardive dyskinesia.
ADRs: dry mouth, blurry vision, nausea, constipation
Benztropine overdose presents with confusion, trouble swallowing, hot and dry skin, dilated pupils, tachycardia, urinary retention, irregular pulse, fainting or seizures.
Antidote = physostigmine

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20
Q

Tetrabenazine

A

Inhibits vesicular monoamine transporter and depletes presynaptic dopamine.
Used for treatment of hyperkinetic movement disorders, such as tardive dyskinesia, hemiballismus, Huntington’s chorea, tics.
Depletes dopamine so can lead to depression/SI.

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21
Q

Bromocriptine

A

Partial D2 agonist
Used in NMS, as well as hyperprolactinaemia and acromegaly

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22
Q

Aripiprazole

A

Partial D2 agonist, 5HT-2A antagonist, partial 5HT-1A agonist.
High affinity for receptor but low intrinsic activity (Goldilock’s effect).
Can be used as augmentation to reduce side effects.
Highly protein bound (99%).
Long half-life (94 hours).
CYP3A4 substrate.

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23
Q

Amisulpride

A

Selective D2/D3 antagonist.
D3 are presynaptic autoreceptors in frontal lobe so antagonism increases dopamine.
At <400mg, amisulpride enhances dopamine transmission.
At higher doses, it blocks D2 and can cause raised PL.
Purely excreted renally. Can be used in hepatic disease. Avoid in renal impairment.
Given BD at doses >300mg to increase therapeutic effect and reduce adverse effects.

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24
Q

Chlorpromazine

A

D1/D2/D3/D4 antagonist
Also acts as antagonist of 5-HT, H1, alpha1-2, M1-M2
Highest risk of sunburn due to increased skin photosensivity

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25
Clozapine - Mechanism + Metabolism
D2 and 5HT-2 antagonist with hit-and-run mechanism (highest dissociation rate) Highest affinity for D4 Potent anticholinergic CYP1A2 - so caffeine increases levels and smoking reduces levels CYP3A4 responsible for 35% of clozapine metabolism - so drug interactions
26
Clozapine - Side effects
- Most epileptogenic antipsychotic - Agranulocytosis (usually first 18 weeks, contraindicated with carbamazepine) - Myocarditis (usually first 8 weeks) - Cardiomyopathy - VTE and PE - Constipation - Tachycardia
27
Flupenthixol
D2 antagonist, also acts on 5HT Typical antipsychotic Antidepressant effect at lower doses Available as depot
28
Haloperidol
D2 antagonist Typical antipsychotic Can be used in renal and hepatic impairment, and in pregnancy (1st line for mania) Indicated for tics in Tourette;s Available as depot
29
Olanzapine
D2 and 5HT-2 antagonist, H1 blockade (sedating) Can be used in renal impairment. CYP1A2 involved (nicotine, caffeine). Half-life 30 hours. Highest passage across placenta of SGAs, associated with high birth weight, macrosomia, increased ICU admissions. Need to monitor for post-injection syndrome.
30
Paliperidone
D2 and 5HT-2 antagonist Major active metabolite of risperidone Low potential for drug interactions as limited hepatic metabolism Half-life 24-28 hours
31
Quetiapine
D2 (higher dissociation so lower risk of EPSE) and 5HT-2 antagonist, H1 blockade (sedating) CYP3A4 involved Half-life 6-12 hours so multiple daily dosing
32
Risperidone
D2 and 5HT-2 antagonist At higher doses, binds selectively to D2 so more risk of EPSE and high PL. Potent alpha-1 blocker so first dose hypotensive effect. Extensive first pass metabolism by CYP2D6 to 9-OH risperidone. Half-life of metabolite = 24 hours. Second highest passage across placenta.
33
Sertindole
Strong D2 and 5HT-2 antagonist Potent alpha-1 blocker Highest potential for QTc prolongation
34
Sulpride
Dose-related antagonist at presynaptic D3 (<800mg/day) and postsynaptic D2 (>800mg/day). Purely renally excreted. Avoid in renal impairment. Recommended in hepatic disease.
35
Trifluoperazine
D1/D2 antagonist Typical antipsychotic
36
Thioridazine
Not available due to highest risk of prolonged QTc
37
Ziprasidone
D2 and 5HT-2 antagonist, 5HT-1A agonist, monoamine reuptake inhibitor Acts as antidepressant at low doses (due to MAOI effect). Reduces weight through 5HT agonism. High risk for prolonged QTc. CYP3A4 involved. Half-life = 7-12 hours.
38
Zuclopenthixol
D1/D2 antagonist, 5HT-2 antagonist, alpha-1 adrenergic Typical antipsychotic Available as decanoate (depot), acetate (accuphase, effect peaks at 48-72 hours) and oral. Interacts with paroxetine due to shared hepatic metabolism.
39
Lurasidone
D2/D3 antagonist, 5HT-2A/5HT-7 antagonist, 5HT-1A partial agonist, alpha-2c antagonist Atypical antipsychotic Used in bipolar depression, alone or as an adjunct. Low risk of weight gain.
40
SSRIs - Mechanism
Block SERT (serotonin reuptake transporter) so serotonin remains in synaptic cleft and can bind to various serotonin receptors. Initially, there is an increase in signaling across synapses that use 5HT as main neurotransmitter. With time, increased occupancy of post-synaptic 5HT receptor downregulates release of 5HT from presynaptic neurons, which ultimately leads to downregulation of postsynaptic 5HT receptors.
41
Serotonin receptors involved in SSRIs
5HT1A = presynaptic autoreceptor, acts as brake. 5HT-2A = postsynaptic receptor, effects include anxiety, akathisia, emotional blunting, insomnia. 5HT-2C = postsynaptic, can lead to sexual dysfunction and anorexia. 5HT-3 = postsynaptic, can lead to nausea and diarrhoea, ligand gated. 5HT-7 = circadian rhythms.
42
SSRIs - side effects
Initial anxiety Sleep disturbance GI upset Headaches Hyponatraemia GI bleeding Sexual dysfunction Side effects dominate when SSRI first started, but they should reduce as receptors down regulate. Paroxetine has most weight gain and sexual side effects.
43
SSRIs - Interactions
Enzyme inhibitors so can increase levels of clozapine, olanzapine, benzos, TCAs, methadone. Do not prescribe with MAOIs due to risk of serotonin syndrome.
44
Mirtazapine - Mechanism
NASSA (NA serotonin specific antagonist) At doses of 15-30mg, it is primarily a serotonin antagonist, so effects are: - 5HT-2A = antianxiety, treats akathisia, improves slow wave sleep - 5HT-2C = increased appetite, no sexual effects - anti-H1 = increased appetite, sedation At doses of 45-60mg, it primarily has a noradrenergic dopaminergic effect, by antagonising alpha-2 presynaptic receptor, increasing NA and dopamine => broad spectrum antidepressant.
45
Mirtazapine - Side effects
Sedation at low doses (H1). Weight gain, increased appetite. Agranulocytosis. Caution in epilepsy. No sexual dysfunction. Minimal risk of serotonin syndrome.
46
SNRIs - Mechanism
SNRIs = venlafaxine, duloxetine. Serotonin noradrenergic reuptake inhibitors. - Block SERT to increase serotonin. - Block NET to increase NA and dopamine. Broad spectrum effect. Half-life 4-5 hours. Venlafaxine predominantly acts as SSRI up to 225mg, then has SNRI effects above that.
47
SNRIs - Side effects
Side effects of both SSRIs and dopamine-related effects (activation, agitation). Sexual dysfunction. Hypertension at doses >225mg. Greater risk of discontinuation syndrome. Caution in epilepsy (seizure risk).
48
Agomelatine - Mechanism
Melatonin agonist (M1/M2) = improves slow wave sleep. 5HT-2C antagonist Also increases frontal lobe dopamine and NA.
49
Agomelatine - Side effects
LFT derangement No risk of serotonin syndrome No sexual dysfunction
50
Tricyclics - Mechanism
Broad spectrum antidepressants Act primarily as SNRIs by blocking SERT and NET. Weak affinity for DAT. Many also have high affinity as 5HT antagonists, alpha-1 adrenergic and NMDA receptors, and as sigma agonists. Also have potent anticholinergic and antihistaminergic effects.
51
Tricyclics - Examples
Amitriptyline, nortriptyline Clomipramine, desipramine, imipramine Dosulepine, doxepine
52
MAOIs - Examples
Non-selective = phenelzine, tranylcypromine Selective MAO-A = moclobemide Selective MAO-B = selegline
53
MAOIs - Mechanism
Broad spectrum antidepressants - Inhibit MAO to prevent breakdown of monoamine neurotransmitters - MAO-A preferentially acts on serotonin, melatonin, adrenaline and NA - MAO-B preferentially acts on phenethylamine and other trace amines - Dopamine equally affected by both
54
MAOIs - Side effects
Hypertensive crisis - which can be fatal. Need to avoid eating food contained tyramine (cheese, fermented food, liver).
55
NARIs
Atomoxetine (used in ADHD) and reboxetine. Noradrenergic reuptake inhibitors Can cause liver failure and SI
56
Vortioxetine
SSRI + serotonin modulator, so blocks SERT to increase serotonin, but with minimal sexual dysfunction or weight gain. 5HT-7 antagonist = pro-cognitive effects.
57
SARIs
Nefazodone and trazodone. Serotonin antagonist and reuptake inhibitor (of 5HT, NA and dopamine). Also antagonist alpha-1 adrenergic receptors.
58
Buspirone
5HT-1A partial agonist with high affinity Acts as a full agonist at presynaptic receptor, to decrease serotonin levels for anti-anxiety effect. Acts as a partial agonist at postsynaptic receptors, for anti-depressant effects. Also a D2 antagonist. Half-life 2-12hours. Can be used in depression, GAD. Main side effect is dizziness (titrate dose slowly).
59
Cyproheptadine
Antihistamine with anti-serotonergic effects (5HT-1 and 2 blockade). Used in treatment of serotonin syndrome
60
Lithium - Mechanism
Acts via "second messenger system". Effects include decreased NA release, increased 5HT synthesis, inhibition of excitatory neurotransmitters (dopamine, glutamate) and promotion of glutamate (inhibitory). Likely has neuroprotective/neuroproliferative effects.
61
Lithium - Pharmacology
Half-life 18-36 hours. Peak plasma concentration at 1-2 hours (standard release) or 4-5 hours (ER). Starting dose 250mg BD or 400mg nocte. Loading dose 20-30mg/kg. Bioavailability 80-100% Follows zero order kinetics Almost exclusively excreted by kidney as free ion
62
Lithium - Indications
Prophylaxis and treatment of mania, hypomania and depression in BPAD Prophylaxis and treatment of unipolar depression Augmentation agent to antidepressants Note full prophylactic effect may take 6-12months
63
Lithium - Plasma levels
Narrow therapeutic/toxic ratio Levels taken on day 7, 12 hours post-dose. Targets: - 0.4-0.6 for tx of depression - 0.6-08 for prophylaxis - 0.8-1.2 for tx of mania
64
Lithium - Toxicity
Level >1.5 Tremor, ataxia, dysarthria, nystagmus, renal impairment, convulsions, death.
65
Lithium - Side effects
Common - polyuria, thirst, tremor, impaired memory/cognition, hair loss, acne Serious - hypothyroidism, hyperparathyroidism, renal damage
66
Lithium - Interactions
Avoid diuretics, ACEIs, ARBs, NSAIDs All increase lithium level
67
Lithium - Pregnancy
Potential risk of fetal heart malformations, especially in 1st trimester. If taken during pregnancy, levels may drop in later stages due to increased GFR. Lithium passes freely into breast milk.
68
Valproate - Mechanism
Unknown, but proposed ideas include affecting GABA levels, blockage of voltage-gated Na+ channels, inhibiting histone deacetylases.
69
Valproate - Pharmacology
Half-life 16 hours Bioavailability close to 100% 90% protein bound (levels may be inaccurate in hypoalbuminaemia, can displace other drugs such as warfarin, phenytoin, carbamazepine) Metabolised by liver Loading dose 20-30mg/kg
70
Valproate - Indications
Treatment of mania, mixed mood episodes, rapid cycling BPAD Prophylaxis in BPAD
71
Valproate - Levels
Not routinely monitored as poor correlation with therapeutic efficacy. May be useful in non-adherence, suspected toxicity. Trough level - 350-700 μmol/L
72
Valproate - Side effects
Common = N+V, dry mouth, somnolence, hair loss, peripheral oedema. Serious = liver failure (monitor LFTs), pancreatitis, increased suicide risk, thrombocytopenia. Can lead to hyperammonaemic encephalopathy in people with disorders of carnitine metabolism.
73
Valproate - Pregnancy
Highly teratogenic Contraindicated in women of childbearing age
74
Valproate - Interactions
Can increase lamotrigine levels by inhibiting gluconuridation
75
Carbamazepine - Mechanism
Blocks voltage-gated Na+ channels, reduces glutamate release, decreases adrenaline/NA turnover
76
Carbamazepine - Pharmacology
Bioavailability 80% Variable absorption 75% bound to plasma protein Induces its own metabolism (CYP3A4)
77
Carbamazepine - Indications
Prophylaxis in BPAD, rapid cycling
78
Carbamazepine - Levels
Trough level 16-40 μmol/L Check 4-6 monthly or if dose adjusted
79
Carbamazepine - Side effects
Common = drowsiness, headaches, N+V, constipation, dizziness Serious = severe skin reactions (SJS, toxic epidermal necrolysis), agranulocytosis, aplastic anaemia, porphyria
80
Carbamazepine - Interactions
- Potent CYP3A4 inducer - interacts with OCP, antipsychotics (can decrease levels), methadone, thyroxine - Levels may be increased by fluoxetine/paroxetine - Contraindicated with clozapine
81
Lamotrigine - Mechanism
Blocks voltage-gated Na+ channels, with secondary effect on Ca2+ transport, leading to membrane stabilisation and decreased glutamate release. Weak 5HT-3 antagonist.
82
Lamotrigine - Pharmacology
Half-life 28 hours 55% protein bound
83
Lamotrigine - Indications
Prevention of depression in BPAD Not effective for mania
84
Lamotrigine -rash
About 8% get a rash in first 4/12 of tx. In 0.1%, this is SJS or TEN, so lamotrigine must be stopped at first sign of a rash. Risk of rash increased with rapid titration, higher doses, co-administration with valproate.
85
Lamotrigine - Interactions
Carbamazepine decreases levels by 50% Valproate increases levels by 50% COCP induces glucuronidation, increasing excretion x3
86
Gabapentin/Pregabalin
Structural analogues of GABA Bind to voltage-gated Na+ channel Act on 1-amino acid transporter and increases GABA availability in brain Anxiolytic, analgesia and anticonvulsant effects
87
Tiagabine
Potent inhibitor of GABA uptake into neuros and glial cells, by selective inhibition of GAT1 (GABA transporter) Used an anticonvulsant, as well as in anxiety and panic disorders
88
Vigabatrin
Selective irreversible GABA-transaminase inhibitor Indicated as anticonvulsant
89
Topiramate
Modifies Na+ and Ca2+ dependent channels Selective inhibitor of kainate-mediated AMPA glutamate receptors Enhances GABA-mediated Cl- flux into neurons Potentiates action of GABA-A receptor Indicated in epilepsy, migraine prophylaxis
90
Benzodiazepines - Mechanism
Enhance effect of GABA on GABA-A receptor to decrease excitability of neurons, resulting in sedative, hypnotic, anxiolytic, anticonvulsant and muscle-relaxant properties
91
Benzodiazepines - half-lives
Short acting = midazolam (half-life 2hrs), triazolam Intermediate acting = clonazepam (half-life 19-60hrs), lorazepam (half-life 10-20hrs) and temazepam Long acting = diazepam (half-life 20-80hrs)
92
Benzodiazepines - Side effects
Withdrawal (due to decreased brain GABA function), tolerance and dependence Drowsiness, dizziness, cognitive impairment (anterograde amnesia) Paradoxical reactions Can precipitate coma in hepatic impairment
93
Z-drugs
Very similar to benzodiazepines Used for anxiolytic and hypnotic effects Mechanism: agonists of GABA-A alpha-1 subunit on omega-1 receptor (also called benzodiazepine-associated receptor), which potentiates GABA Similar benefits, risks and side effects to benzos
94
Prazosin
Alpha-2 presynaptic agonist Reduces NA in brain to help with hyperarousal and nightmares
95
Clonidine
Alpha-2 adrenergic agonist
96
Melatonin
Hormone released from pineal gland Melatonin 1 and 2 receptor agonist Mixed evidence of efficacy for sleep Half-life 3-4 hours
97
Promethazine
H1 receptor antagonist, anticholinergic Side effects = headache, antimuscarinic effects, psychomotor impairment, excitation in young/old
98
Methylphenidate
Ritalin = immediate release Concerta = sustained release Side effects: tachycardia, hypertension, anorexia, dry mouth, GI effects First line for ADHD
99
N-acetylcysteine
Used for paracetamol overdose Reduces oxidative and neuroinflammatory stress Can also be used as augmentation agent in mood disorders, especially BPAD
100
Dantrolene
Direct or indirect ryanodine receptor antagonist, to decrease intracellular Ca2+ and relax muscles Used in treatment of rigidity in NMS
101
Flumenazil
Selective GABA-A receptor antagonist Used as antagonist and antidote to benzodiazepines, through competitive inhibition
102
Desfuroxamine
Used as antidote in iron overdose
103
BAL
Dimercaprol or British anti-Lewisite Used as antidote in arsenic and lead poisoning
104
Sodium bicarbonate
Used to prevent metabolic acidosis in overdose of TCAs
105
Thyroxine
Usual maintenance dose 100mcg Half-life of 7-10 days, but much longer biological effect Children require larger doses by bodyweight
106
SSRIs - Half-life
Fluoxetine has longest half-life = 5-7 days (washout period is about 35 days). Least likely to cause discontinuation sx. Paroxetine has shortest half-life (21hrs) so has highest risk of discontinuation sx. Other SSRIs have half-life of 20-72 hours (so washout period about 2 weeks)
107
Ketamine
NMDA receptor antagonist In sub-anaesthetic doses, it non-competitively binds to NMDA receptors as an antagonist
108
Baclofen
GABA-B agonist Used as a muscle relaxant and to reduce alcohol cravings
109
Sildenafil
Phosphodiesterase inhibitor Binds to PDE5 competitively, and inhibit cGMP hydrolysis, leading to an erection.
110
Zero order kinetics
When the clearance system is saturated, a constant amount is eliminated. This means the levels in the body will increase with increase in doses, so toxicity can occur. For example; phenytoin, lithium, depots, alcohol.
111
First order kinetics
A constant fraction of the drug is eliminated regardless of dose. The rate of clearance only depends on concentration. Most psychotropics are excreted via first order kinetics.
112
Bioavailability
The fraction of the dose that reaches systemic circulation
113
Bioequivalence
Measure of the comparability of plasma levels of two different formulations of the same active drug
114
Non-competitive antagonist
Binds to receptor at site distinct from active site, and induces a confirmational change in receptor which alters the affinity of the receptor for the endogenous ligand, so that effects cannot be reversed completely by increasing the dose of agonist.
115
Irreversible antagonist
Binds to the receptor but cannot be displaced
116
Tigabine
A potent inhibitor of GABA uptake into neurons and glial cells, by inhibiting GAT-1, a GABA transporter. Anticonvulsant.
117
Caffeine
Acts as antagonist of adenosine A1 receptors Half-life 4-6 hours
118
Beta-blockers
Overdose leads to hypoglycaemia Hence treat with glucagon
119
Antidepressant recommended post-MI
Sertraline
120
CYP1A2
Involved in metabolism of clozapine, olanzapine. Inducers = smoking Inhibitors = caffeine, grapefruit, fluvoxamine, ciprofloxacin
121
CYP2D6
Involved in metabolism of risperidone, codeine. Inhibitors = SSRIs (especially paroxetine, fluoxetine) Significant ethnic differences in rate of metabolism/enzyme levels
122
CYP3A4
Involved in metabolism of clozapine, quetiapine, ziprasidone, carbamazepine Inducers = carbamazepine, phenytoin, barbituates, rifampicin Inhibitors = erythromycin, ketoconazole, protease inhibitors
123
CYP2C19
Inhibitors = fluoxetine, fluvoxamine Ethnic differences (20% of Japanese/Chinese are deficient)

Psych MCQs (10 decks)

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