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Pharmacology > 20 Neurodegenerative disorders > Flashcards

20 Neurodegenerative disorders Flashcards

1
Q

20.01 DRUGS USED IN PARKINSON’S DISEASE

Levodopa (co-beneldopa, co-careldopa) - actions

A

relieves the symptoms of Parkinson’s disease by being decarboxylated to dopamine in the brain

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2
Q

20.01 DRUGS USED IN PARKINSON’S DISEASE

Levodopa (co-beneldopa, co-careldopa) - MOA

A

decarboxylation of levodopa to dopamine restores some activity in the nigrostriatal pathway
given with a peripheral dopa decarboxylase inhibitor (benserazide or carbidopa), which inhibits levodopa decarboxylation outside the brain
this allows the use of smaller doses and reduces peripheral side effects of dopamine

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3
Q

20.01 DRUGS USED IN PARKINSON’S DISEASE

Levodopa (co-beneldopa, co-careldopa) - abs/distrib/elim

A

given orally
levodopa half-life is 1-2h when co-administered with carbidopa

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4
Q

20.01 DRUGS USED IN PARKINSON’S DISEASE

Levodopa (co-beneldopa, co-careldopa) - clinical use

A

first-line treatment in Parkinson’s disease
more effective against akinesia and rigidity than against tremor
effectiveness diminishes over some months to a few years

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5
Q

20.01 DRUGS USED IN PARKINSON’S DISEASE

Levodopa (co-beneldopa, co-careldopa) - adverse effects

A

anorexia, nausea and vomiting
postural hypotension
hallucinations, daytime somnolence
more slowly developing effects: dyskinesia (in most patients after 2 years) and ‘on-off’ effects (rapid fluctuations between dyskinesia and hypokinesia/rigidity)
peripheral neuropathy

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6
Q

20.01 DRUGS USED IN PARKINSON’S DISEASE

Levodopa (co-beneldopa, co-careldopa) - special notes

A

sudden withdrawal may cause neuroleptic malignant syndrome

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7
Q

20.02 DRUGS USED IN PARKINSON’S DISEASE

Dopamine agonists: pramipexole, ropinirole, rotigotine, pergolide, apomorphine - actions

A

direct stimulation of post-synaptic dopamine receptors

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8
Q

20.02 DRUGS USED IN PARKINSON’S DISEASE

Dopamine agonists: pramipexole, ropinirole, rotigotine, pergolide, apomorphine - MOA

A

two main types of dopamine agonists: ‘ergot’ agonists (have an ergoline structure) and ‘non-ergot’ agonists
non-ergot agonists are D2/3 selective and stimulate striatal dopamine receptors
ergot agonists have potent and long-lasting dopamine D2 receptor agonist properties
in addition, cabergoline exerts a central dopaminergic effect via D2 receptor stimulation

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9
Q

20.02 DRUGS USED IN PARKINSON’S DISEASE

Dopamine agonists: pramipexole, ropinirole, rotigotine, pergolide, apomorphine - abs/distrib/elim

A

given orally
short plasma half-life (6-8h), requiring three times daily dosing
slow-release (once a day) formulations are now available
rotigotine is given via transdermal patch
apomorphine can be given via SC injection or continuous SC infusion via an external pump

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10
Q

20.02 DRUGS USED IN PARKINSON’S DISEASE

Dopamine agonists: pramipexole, ropinirole, rotigotine, pergolide, apomorphine - clinical use

A

motor symptoms of Parkinson’s disease
apomorphine is used in advanced Parkinson’s disease

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11
Q

20.02 DRUGS USED IN PARKINSON’S DISEASE

Dopamine agonists: pramipexole, ropinirole, rotigotine, pergolide, apomorphine - adverse effects

A

rarely show the same long-term effects of levodopa (dyskinesia, ‘on-off’ fluctuations)
ergot agonists (especially pergolide) are associated with fibrosis (lung, heart, retroperitoneum) and need cardiorespiratory monitoring
nausea and vomiting
sleep disturbances
impulse control disorders
haemolytic anaemia is a rare adverse effect of apomorphine infusion

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12
Q

20.03 DRUGS USED IN PARKINSON’S DISEASE

Catechol-O-methyl transferase (COMT) inhibitors: entacapone, tolcapone - actions

A

synergises with the antiparkinsonian effects of levodopa/carbidopa
potentiates actions of catecholamines

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13
Q

20.03 DRUGS USED IN PARKINSON’S DISEASE

Catechol-O-methyl transferase (COMT) inhibitors: entacapone, tolcapone - MOA

A

reversible inhibition of COMT in the periphery reduces levodopa breakdown (like peripheral dopa decarboxylase inhibitors) allowing more of levodopa dose to penetrate brain

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14
Q

20.03 DRUGS USED IN PARKINSON’S DISEASE

Catechol-O-methyl transferase (COMT) inhibitors: entacapone, tolcapone - abs/distrib/elim

A

given orally
short half-life (1h) necessitates dosing several times/day

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15
Q

20.03 DRUGS USED IN PARKINSON’S DISEASE

Catechol-O-methyl transferase (COMT) inhibitors: entacapone, tolcapone - clinical use

A

adjunct to levodopa/carbidopa therapy - especially for patients showing ‘end-of-dose’ symptoms (no antiparkinsonian effect by itself)

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16
Q

20.03 DRUGS USED IN PARKINSON’S DISEASE

Catechol-O-methyl transferase (COMT) inhibitors: entacapone, tolcapone - adverse effects

A

exacerbates adverse effects of levodopa/carbidopa taken at the same time
dyskinesia, nausea, diarrhoea
postural hypotension
hallucinations
anxiety and sleepiness

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17
Q

20.04 DRUGS USED IN PARKINSON’S DISEASE

Monoamine oxidase (MAOB) inhibitors: selegiline, rasagiline - actions

A

prevent breakdown of dopamine in synapses

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18
Q

20.04 DRUGS USED IN PARKINSON’S DISEASE

Monoamine oxidase (MAOB) inhibitors: selegiline, rasagiline - MOA

A

selective irreversible inhibition of MAOB, the isozyme which has dopamine as a preferred substrate
potentiates action of endogenous dopamine and dopamine formed from administered levodopa

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19
Q

20.04 DRUGS USED IN PARKINSON’S DISEASE

Monoamine oxidase (MAOB) inhibitors: selegiline, rasagiline - abs/distrib/elim

A

given orally (but low bioavailability)
half-lives: selegiline 2h, rasagiline 3h

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20
Q

20.04 DRUGS USED IN PARKINSON’S DISEASE

Monoamine oxidase (MAOB) inhibitors: selegiline, rasagiline - clinical use

A

adjunct to levodopa/carbidopa, as their effect wanes, in Parkinson’s disease
irreversible nature of MAO inhibition prolongs effects of drug for some days
also approved for major depression

21
Q

20.04 DRUGS USED IN PARKINSON’S DISEASE

Monoamine oxidase (MAOB) inhibitors: selegiline, rasagiline - adverse effects

A

adverse effects mainly due to increased action of levodopa taken concurrently: nausea, dyskinesia, depression, insomnia, postural hypotension, hallucinations, confusion
if dose >10 mg, selegiline can block MAOA - the enzyme involved in the metabolism of tyramine-containing foods (cheese, red wine) which can result in hypertensive crisis
severe interactions may occur with tricyclic and SSRI antidepressants

22
Q

20.05 DRUGS USED IN PARKINSON’S DISEASE

Antiviral agent: amantadine - actions

A

anti-dyskinetic drug, originally developed as an antiviral

23
Q

20.05 DRUGS USED IN PARKINSON’S DISEASE

Antiviral agent: amantadine - MOA

A

thought to act by increasing dopamine release from nerve endings in striatum
antimuscarinic actions, like those of benztropine, may also contribute
more recently, block of NMDA receptors by stabilising closed states of the channel has been described

24
Q

20.05 DRUGS USED IN PARKINSON’S DISEASE

Antiviral agent: amantadine - abs/distrib/elim

A

given orally
mostly excreted unchanged in urine
half-life 17h

25
Q

20.05 DRUGS USED IN PARKINSON’S DISEASE

Antiviral agent: amantadine - clinical use

A

Parkinson’s disease
generally less effective than levodopa, dopamine agonists or MAOB inhibitors
effective against the dyskinesia associated with levodopa therapy
(antiviral action is used for influenza infection)

26
Q

20.05 DRUGS USED IN PARKINSON’S DISEASE

Antiviral agent: amantadine - adverse effects

A

nausea, dizziness, insomnia
postural hypotension
anxiety, confusion, hallucinations
antimuscarinic action is important contributor to death from overdose

27
Q

20.06 DRUGS USED IN PARKINSON’S DISEASE

Centrally acting muscarinic antagonists: benztropine, trihexyphenidyl, orphenadrine, procyclidine - actions

A

to treat tremor in Parkinson’s disease

28
Q

20.06 DRUGS USED IN PARKINSON’S DISEASE

Centrally acting muscarinic antagonists: benztropine, trihexyphenidyl, orphenadrine, procyclidine - MOA

A

reduces muscarinic actions of acetylcholine in striatum
(restores ‘balance’ between dopaminergic and cholinergic activities)
action is probably on M1 receptors

29
Q

20.06 DRUGS USED IN PARKINSON’S DISEASE

Centrally acting muscarinic antagonists: benztropine, trihexyphenidyl, orphenadrine, procyclidine - abs/distrib/elim

A

orally active
half-lives: benztropine ~36h, trihexyphenidyl 3-4h

30
Q

20.06 DRUGS USED IN PARKINSON’S DISEASE

Centrally acting muscarinic antagonists: benztropine, trihexyphenidyl, orphenadrine, procyclidine - clinical use

A

now rarely used for Parkinson’s disease
much less effective than those drugs increasing dopaminergic transmission, but has value in treating tremor
used in antipsychotic-induced parkinsonism and acute dykinesias

31
Q

20.06 DRUGS USED IN PARKINSON’S DISEASE

Centrally acting muscarinic antagonists: benztropine, trihexyphenidyl, orphenadrine, procyclidine - adverse effects

A

confusion - best avoided in older patients
effects due to parasympathetic block - dry mouth, inhibition of peristalsis, raised intraocular pressure (avoid in narrow-angle glaucoma), blurred vision, urinary retention, tachycardia, etc.

32
Q

20.07 DRUGS USED IN ALZHEIMER’S DISEASE

Cholinesterase inhibitors: donepezil, rivastigmine, galantamine - actions

A

ameliorate symptoms of Alzheimer’s disease

33
Q

20.07 DRUGS USED IN ALZHEIMER’S DISEASE

Cholinesterase inhibitors: donepezil, rivastigmine, galantamine - MOA

A

reversible inhibition of acetylcholinesterase
enhance cholinergic transmission in the cerebral cortex and hippocampus

34
Q

20.07 DRUGS USED IN ALZHEIMER’S DISEASE

Cholinesterase inhibitors: donepezil, rivastigmine, galantamine - abs/distrib/elim

A

orally active
half-lives: donepezil 70h, rivastigmine 1.5h, galantamine 7h

35
Q

20.07 DRUGS USED IN ALZHEIMER’S DISEASE

Cholinesterase inhibitors: donepezil, rivastigmine, galantamine - clinical use

A

mild to moderate Alzheimer’s disease, providing limited relief from the symptoms but having no effect on disease progression

36
Q

20.07 DRUGS USED IN ALZHEIMER’S DISEASE

Cholinesterase inhibitors: donepezil, rivastigmine, galantamine - adverse effects

A

predictable parasympathomimetic side effects: nausea, diarrhoea, vomiting, bradycardia (baseline ECG required), increased gastric acid secretion
anorexia with weight loss and insomnia also occur

37
Q

20.08 DRUGS USED IN ALZHEIMER’S DISEASE

N-methyl-D-aspartate (NMDA) receptor antagonist: memantine - actions

A

originally developed as an antiviral drug
potential inhibitor of excitotoxicity

38
Q

20.08 DRUGS USED IN ALZHEIMER’S DISEASE

N-methyl-D-aspartate (NMDA) receptor antagonist: memantine - MOA

A

open-channel block of NMDA receptors
prevents Na+ and, more importantly, Ca2+ entry into the neuron, so reducing glutamate excitotoxicity
normal glutamatergic transmission continues

39
Q

20.08 DRUGS USED IN ALZHEIMER’S DISEASE

N-methyl-D-aspartate (NMDA) receptor antagonist: memantine - abs/distrib/elim

A

oral administration
half-life 60-80h

40
Q

20.08 DRUGS USED IN ALZHEIMER’S DISEASE

N-methyl-D-aspartate (NMDA) receptor antagonist: memantine - clinical use

A

moderate to severe Alzheimer’s disease
provides only symptomatic relief of the cognitive and memory impairment of the disease
no effect on the degenerative process
can be used in combination with centrally acting anticholinesterases

41
Q

20.08 DRUGS USED IN ALZHEIMER’S DISEASE

N-methyl-D-aspartate (NMDA) receptor antagonist: memantine - adverse effects

A

usually well tolerated
confusion, dizziness, drowsiness, headache, insomnia, agitation, hallucinations

42
Q

20.09 DRUGS USED IN MULTIPLE SCLEROSIS

Glatiramer acetate - multiple sclerosis

A

interferes with immune response to myelin
given by SC injection
reduces relapses

43
Q

20.09 DRUGS USED IN MULTIPLE SCLEROSIS

Dimethyl fumarate - multiple sclerosis

A

given orally
reduces relapse rate and slows progression

44
Q

20.09 DRUGS USED IN MULTIPLE SCLEROSIS

Fingolimod - multiple sclerosis

A

inhibits cytotoxic CD8-expressing T cells
given orally
reduces relapse rate, but increases risk of progressive multifocal leukoencephalopathy (PML) and ventricular arrhythmias

45
Q

20.09 DRUGS USED IN MULTIPLE SCLEROSIS

Beta-interferons - multiple sclerosis

A

modulate immune response
given by SC or IM injection
reduces relapse rate

46
Q

20.09 DRUGS USED IN MULTIPLE SCLEROSIS

Natalizumab - multiple sclerosis

A

monoclonal antibody (α4-integrin)
IV infusion (monthly)
slows progression of disability in relapsing MS
can cause PML

47
Q

20.09 DRUGS USED IN MULTIPLE SCLEROSIS

Alemtuzumab - multiple sclerosis

A

monoclonal antibody (CD52)
IV infusion

48
Q

20.09 DRUGS USED IN MULTIPLE SCLEROSIS

Ocrelizumab - multiple sclerosis

A

monoclonal antibody (CD20)
IV infusion

Pharmacology (34 decks)

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